US20070125657A1 - Method of direct plating of copper on a substrate structure - Google Patents
Method of direct plating of copper on a substrate structure Download PDFInfo
- Publication number
- US20070125657A1 US20070125657A1 US11/255,368 US25536805A US2007125657A1 US 20070125657 A1 US20070125657 A1 US 20070125657A1 US 25536805 A US25536805 A US 25536805A US 2007125657 A1 US2007125657 A1 US 2007125657A1
- Authority
- US
- United States
- Prior art keywords
- copper
- substrate surface
- plating
- layer
- copper layer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000010949 copper Substances 0.000 title claims abstract description 192
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 title claims abstract description 179
- 229910052802 copper Inorganic materials 0.000 title claims abstract description 178
- 239000000758 substrate Substances 0.000 title claims abstract description 146
- 238000000034 method Methods 0.000 title claims abstract description 131
- 238000007747 plating Methods 0.000 title claims description 157
- 238000000151 deposition Methods 0.000 claims abstract description 105
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 claims abstract description 25
- 239000002253 acid Substances 0.000 claims abstract description 24
- 229910001431 copper ion Inorganic materials 0.000 claims abstract description 24
- 230000002378 acidificating effect Effects 0.000 claims abstract description 15
- 239000010410 layer Substances 0.000 claims description 277
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 claims description 36
- 229910052707 ruthenium Inorganic materials 0.000 claims description 36
- 239000011229 interlayer Substances 0.000 claims description 32
- MZLGASXMSKOWSE-UHFFFAOYSA-N tantalum nitride Chemical compound [Ta]#N MZLGASXMSKOWSE-UHFFFAOYSA-N 0.000 claims description 21
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 20
- 230000006911 nucleation Effects 0.000 claims description 19
- 238000010899 nucleation Methods 0.000 claims description 18
- 229910052715 tantalum Inorganic materials 0.000 claims description 18
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims description 18
- 229910001362 Ta alloys Inorganic materials 0.000 claims description 16
- -1 tungsten nitride Chemical class 0.000 claims description 16
- CMIQNFUKBYANIP-UHFFFAOYSA-N ruthenium tantalum Chemical compound [Ru].[Ta] CMIQNFUKBYANIP-UHFFFAOYSA-N 0.000 claims description 10
- 229910052721 tungsten Inorganic materials 0.000 claims description 10
- 239000010937 tungsten Substances 0.000 claims description 10
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 9
- 239000010948 rhodium Substances 0.000 claims description 9
- 229910017052 cobalt Inorganic materials 0.000 claims description 7
- 239000010941 cobalt Substances 0.000 claims description 7
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical group [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 7
- 239000008139 complexing agent Substances 0.000 claims description 6
- 229910052741 iridium Inorganic materials 0.000 claims description 6
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 claims description 6
- 229910052762 osmium Inorganic materials 0.000 claims description 6
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 claims description 6
- 229910052703 rhodium Inorganic materials 0.000 claims description 6
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 claims description 6
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 5
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical compound [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 claims description 5
- 229910001080 W alloy Inorganic materials 0.000 claims description 5
- 229940079895 copper edta Drugs 0.000 claims description 5
- BDXBEDXBWNPQNP-UHFFFAOYSA-L copper;2-[2-[bis(carboxylatomethyl)amino]ethyl-(carboxylatomethyl)amino]acetate;hydron Chemical compound [Cu+2].OC(=O)CN(CC([O-])=O)CCN(CC(O)=O)CC([O-])=O BDXBEDXBWNPQNP-UHFFFAOYSA-L 0.000 claims description 5
- FWBOFUGDKHMVPI-UHFFFAOYSA-K dicopper;2-oxidopropane-1,2,3-tricarboxylate Chemical compound [Cu+2].[Cu+2].[O-]C(=O)CC([O-])(C([O-])=O)CC([O-])=O FWBOFUGDKHMVPI-UHFFFAOYSA-K 0.000 claims description 5
- 239000010936 titanium Substances 0.000 claims description 5
- 229910052719 titanium Inorganic materials 0.000 claims description 5
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 5
- UGACIEPFGXRWCH-UHFFFAOYSA-N [Si].[Ti] Chemical compound [Si].[Ti] UGACIEPFGXRWCH-UHFFFAOYSA-N 0.000 claims description 4
- HWEYZGSCHQNNEH-UHFFFAOYSA-N silicon tantalum Chemical compound [Si].[Ta] HWEYZGSCHQNNEH-UHFFFAOYSA-N 0.000 claims description 4
- 230000004888 barrier function Effects 0.000 abstract description 73
- 229910052751 metal Inorganic materials 0.000 abstract description 43
- 239000002184 metal Substances 0.000 abstract description 43
- 230000002829 reductive effect Effects 0.000 abstract description 10
- 239000003870 refractory metal Substances 0.000 abstract description 4
- 230000008021 deposition Effects 0.000 description 79
- 238000012545 processing Methods 0.000 description 47
- 239000000243 solution Substances 0.000 description 44
- 239000010408 film Substances 0.000 description 26
- 150000001875 compounds Chemical class 0.000 description 21
- 238000002203 pretreatment Methods 0.000 description 20
- 238000005240 physical vapour deposition Methods 0.000 description 15
- 230000015572 biosynthetic process Effects 0.000 description 10
- 238000005229 chemical vapour deposition Methods 0.000 description 10
- 239000003792 electrolyte Substances 0.000 description 10
- 239000000463 material Substances 0.000 description 10
- 238000007254 oxidation reaction Methods 0.000 description 9
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 8
- 239000003446 ligand Substances 0.000 description 8
- 230000003647 oxidation Effects 0.000 description 8
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 8
- 238000000231 atomic layer deposition Methods 0.000 description 7
- 230000008901 benefit Effects 0.000 description 7
- 239000013078 crystal Substances 0.000 description 7
- 239000002585 base Substances 0.000 description 6
- 230000000536 complexating effect Effects 0.000 description 6
- 239000008151 electrolyte solution Substances 0.000 description 6
- 238000009713 electroplating Methods 0.000 description 6
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 description 5
- 239000000654 additive Substances 0.000 description 5
- 230000000996 additive effect Effects 0.000 description 5
- 239000003002 pH adjusting agent Substances 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 4
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 4
- 239000000356 contaminant Substances 0.000 description 4
- 238000011109 contamination Methods 0.000 description 4
- 238000004070 electrodeposition Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 150000002739 metals Chemical class 0.000 description 4
- 239000011734 sodium Substances 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 239000003929 acidic solution Substances 0.000 description 3
- 239000012670 alkaline solution Substances 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 150000007942 carboxylates Chemical class 0.000 description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- 238000012864 cross contamination Methods 0.000 description 3
- 230000001419 dependent effect Effects 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000007772 electroless plating Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 229910021645 metal ion Inorganic materials 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 229910052763 palladium Inorganic materials 0.000 description 3
- 229910052697 platinum Inorganic materials 0.000 description 3
- 238000006722 reduction reaction Methods 0.000 description 3
- 229910001925 ruthenium oxide Inorganic materials 0.000 description 3
- WOCIAKWEIIZHES-UHFFFAOYSA-N ruthenium(iv) oxide Chemical compound O=[Ru]=O WOCIAKWEIIZHES-UHFFFAOYSA-N 0.000 description 3
- 239000004065 semiconductor Substances 0.000 description 3
- 239000000080 wetting agent Substances 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 2
- RPNUMPOLZDHAAY-UHFFFAOYSA-N Diethylenetriamine Chemical compound NCCNCCN RPNUMPOLZDHAAY-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- ATHHXGZTWNVVOU-UHFFFAOYSA-N N-methylformamide Chemical compound CNC=O ATHHXGZTWNVVOU-UHFFFAOYSA-N 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 229910019897 RuOx Inorganic materials 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 238000013459 approach Methods 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 238000005137 deposition process Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
- XLYOFNOQVPJJNP-ZSJDYOACSA-N heavy water Substances [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 238000001465 metallisation Methods 0.000 description 2
- 150000007522 mineralic acids Chemical class 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 239000001508 potassium citrate Substances 0.000 description 2
- 229960002635 potassium citrate Drugs 0.000 description 2
- QEEAPRPFLLJWCF-UHFFFAOYSA-K potassium citrate (anhydrous) Chemical compound [K+].[K+].[K+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O QEEAPRPFLLJWCF-UHFFFAOYSA-K 0.000 description 2
- 235000011082 potassium citrates Nutrition 0.000 description 2
- LWIHDJKSTIGBAC-UHFFFAOYSA-K potassium phosphate Substances [K+].[K+].[K+].[O-]P([O-])([O-])=O LWIHDJKSTIGBAC-UHFFFAOYSA-K 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 229910052814 silicon oxide Inorganic materials 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- LPMBTLLQQJBUOO-KTKRTIGZSA-N (z)-n,n-bis(2-hydroxyethyl)octadec-9-enamide Chemical compound CCCCCCCC\C=C/CCCCCCCC(=O)N(CCO)CCO LPMBTLLQQJBUOO-KTKRTIGZSA-N 0.000 description 1
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- 239000004254 Ammonium phosphate Substances 0.000 description 1
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-M Bisulfite Chemical compound OS([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-M 0.000 description 1
- 239000004135 Bone phosphate Substances 0.000 description 1
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- KRKNYBCHXYNGOX-UHFFFAOYSA-K Citrate Chemical compound [O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O KRKNYBCHXYNGOX-UHFFFAOYSA-K 0.000 description 1
- 235000013162 Cocos nucifera Nutrition 0.000 description 1
- 244000060011 Cocos nucifera Species 0.000 description 1
- FEWJPZIEWOKRBE-JCYAYHJZSA-N Dextrotartaric acid Chemical compound OC(=O)[C@H](O)[C@@H](O)C(O)=O FEWJPZIEWOKRBE-JCYAYHJZSA-N 0.000 description 1
- IAYPIBMASNFSPL-UHFFFAOYSA-N Ethylene oxide Chemical compound C1CO1 IAYPIBMASNFSPL-UHFFFAOYSA-N 0.000 description 1
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- AFVFQIVMOAPDHO-UHFFFAOYSA-N Methanesulfonic acid Chemical compound CS(O)(=O)=O AFVFQIVMOAPDHO-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- GOOHAUXETOMSMM-UHFFFAOYSA-N Propylene oxide Chemical compound CC1CO1 GOOHAUXETOMSMM-UHFFFAOYSA-N 0.000 description 1
- 229910021607 Silver chloride Inorganic materials 0.000 description 1
- 229920002125 Sokalan® Polymers 0.000 description 1
- ROZSPJBPUVWBHW-UHFFFAOYSA-N [Ru]=O Chemical class [Ru]=O ROZSPJBPUVWBHW-UHFFFAOYSA-N 0.000 description 1
- 235000011054 acetic acid Nutrition 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 125000003545 alkoxy group Chemical group 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 150000001408 amides Chemical group 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- 150000001413 amino acids Chemical class 0.000 description 1
- 239000000908 ammonium hydroxide Substances 0.000 description 1
- VBIXEXWLHSRNKB-UHFFFAOYSA-N ammonium oxalate Chemical compound [NH4+].[NH4+].[O-]C(=O)C([O-])=O VBIXEXWLHSRNKB-UHFFFAOYSA-N 0.000 description 1
- ZRIUUUJAJJNDSS-UHFFFAOYSA-N ammonium phosphates Chemical class [NH4+].[NH4+].[NH4+].[O-]P([O-])([O-])=O ZRIUUUJAJJNDSS-UHFFFAOYSA-N 0.000 description 1
- 235000019289 ammonium phosphates Nutrition 0.000 description 1
- 239000002518 antifoaming agent Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- NHJPVZLSLOHJDM-UHFFFAOYSA-N azane;butanedioic acid Chemical compound [NH4+].[NH4+].[O-]C(=O)CCC([O-])=O NHJPVZLSLOHJDM-UHFFFAOYSA-N 0.000 description 1
- NGPGDYLVALNKEG-UHFFFAOYSA-N azanium;azane;2,3,4-trihydroxy-4-oxobutanoate Chemical compound [NH4+].[NH4+].[O-]C(=O)C(O)C(O)C([O-])=O NGPGDYLVALNKEG-UHFFFAOYSA-N 0.000 description 1
- 239000003637 basic solution Substances 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 229910052792 caesium Inorganic materials 0.000 description 1
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000002738 chelating agent Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 229960004106 citric acid Drugs 0.000 description 1
- 235000015165 citric acid Nutrition 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000001010 compromised effect Effects 0.000 description 1
- 150000004699 copper complex Chemical class 0.000 description 1
- 229910000365 copper sulfate Inorganic materials 0.000 description 1
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- PEVJCYPAFCUXEZ-UHFFFAOYSA-J dicopper;phosphonato phosphate Chemical compound [Cu+2].[Cu+2].[O-]P([O-])(=O)OP([O-])([O-])=O PEVJCYPAFCUXEZ-UHFFFAOYSA-J 0.000 description 1
- UZLGHNUASUZUOR-UHFFFAOYSA-L dipotassium;3-carboxy-3-hydroxypentanedioate Chemical compound [K+].[K+].OC(=O)CC(O)(C([O-])=O)CC([O-])=O UZLGHNUASUZUOR-UHFFFAOYSA-L 0.000 description 1
- CVOQYKPWIVSMDC-UHFFFAOYSA-L dipotassium;butanedioate Chemical compound [K+].[K+].[O-]C(=O)CCC([O-])=O CVOQYKPWIVSMDC-UHFFFAOYSA-L 0.000 description 1
- IRXRGVFLQOSHOH-UHFFFAOYSA-L dipotassium;oxalate Chemical compound [K+].[K+].[O-]C(=O)C([O-])=O IRXRGVFLQOSHOH-UHFFFAOYSA-L 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 150000004677 hydrates Chemical class 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 150000004715 keto acids Chemical group 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 238000001459 lithography Methods 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 238000004377 microelectronic Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 235000005985 organic acids Nutrition 0.000 description 1
- 239000006259 organic additive Substances 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 235000006408 oxalic acid Nutrition 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 235000021317 phosphate Nutrition 0.000 description 1
- 235000011007 phosphoric acid Nutrition 0.000 description 1
- 229920002401 polyacrylamide Polymers 0.000 description 1
- 229920005646 polycarboxylate Polymers 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 229920000570 polyether Polymers 0.000 description 1
- 229960003975 potassium Drugs 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- KYKNRZGSIGMXFH-ZVGUSBNCSA-M potassium bitartrate Chemical compound [K+].OC(=O)[C@H](O)[C@@H](O)C([O-])=O KYKNRZGSIGMXFH-ZVGUSBNCSA-M 0.000 description 1
- 235000011009 potassium phosphates Nutrition 0.000 description 1
- 159000000001 potassium salts Chemical class 0.000 description 1
- 239000001472 potassium tartrate Substances 0.000 description 1
- 229940111695 potassium tartrate Drugs 0.000 description 1
- 235000011005 potassium tartrates Nutrition 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical class [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 1
- NLJMYIDDQXHKNR-UHFFFAOYSA-K sodium citrate Chemical compound O.O.[Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NLJMYIDDQXHKNR-UHFFFAOYSA-K 0.000 description 1
- 229960000999 sodium citrate dihydrate Drugs 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 229940095064 tartrate Drugs 0.000 description 1
- YWYZEGXAUVWDED-UHFFFAOYSA-N triammonium citrate Chemical compound [NH4+].[NH4+].[NH4+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O YWYZEGXAUVWDED-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D3/00—Electroplating: Baths therefor
- C25D3/02—Electroplating: Baths therefor from solutions
- C25D3/38—Electroplating: Baths therefor from solutions of copper
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
- C25D5/10—Electroplating with more than one layer of the same or of different metals
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
- C25D5/34—Pretreatment of metallic surfaces to be electroplated
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
- C25D5/60—Electroplating characterised by the structure or texture of the layers
- C25D5/615—Microstructure of the layers, e.g. mixed structure
- C25D5/617—Crystalline layers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/28—Manufacture of electrodes on semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/268
- H01L21/283—Deposition of conductive or insulating materials for electrodes conducting electric current
- H01L21/288—Deposition of conductive or insulating materials for electrodes conducting electric current from a liquid, e.g. electrolytic deposition
- H01L21/2885—Deposition of conductive or insulating materials for electrodes conducting electric current from a liquid, e.g. electrolytic deposition using an external electrical current, i.e. electro-deposition
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
- H01L21/76841—Barrier, adhesion or liner layers
- H01L21/76843—Barrier, adhesion or liner layers formed in openings in a dielectric
- H01L21/76846—Layer combinations
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
- H01L21/76841—Barrier, adhesion or liner layers
- H01L21/76868—Forming or treating discontinuous thin films, e.g. repair, enhancement or reinforcement of discontinuous thin films
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
- H01L21/76841—Barrier, adhesion or liner layers
- H01L21/76871—Layers specifically deposited to enhance or enable the nucleation of further layers, i.e. seed layers
- H01L21/76873—Layers specifically deposited to enhance or enable the nucleation of further layers, i.e. seed layers for electroplating
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
- H01L21/76877—Filling of holes, grooves or trenches, e.g. vias, with conductive material
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/52—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames
- H01L23/522—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body
- H01L23/532—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body characterised by the materials
- H01L23/53204—Conductive materials
- H01L23/53209—Conductive materials based on metals, e.g. alloys, metal silicides
- H01L23/53228—Conductive materials based on metals, e.g. alloys, metal silicides the principal metal being copper
- H01L23/53238—Additional layers associated with copper layers, e.g. adhesion, barrier, cladding layers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/0001—Technical content checked by a classifier
- H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
Definitions
- Embodiments of the present invention generally relate to a method to deposit a metal layer with electrochemical plating and more particularly, to the direct plating of a copper layer onto a barrier or adhesion layer.
- Metallization for sub-quarter micron sized features is a foundational technology for present and future generations of integrated circuit manufacturing processes.
- the multilevel interconnects that lie at the heart of these devices are generally formed by filling high aspect ratio interconnect features with a conductive material (e.g., copper or aluminum).
- a conductive material e.g., copper or aluminum.
- CVD chemical vapor deposition
- PVD physical vapor deposition
- plating techniques such as electrochemical plating (ECP) and electroless plating have emerged as viable processes for filling sub-quarter micron sized, high aspect ratio interconnect features in integrated circuit manufacturing processes.
- ECP processes are generally two stage processes, wherein a seed layer is first formed over the surface features of the substrate (this process may be performed in a separate system), and then the substrate surface features are exposed to an electrolyte solution while an electrical bias is simultaneously applied between the substrate and an anode positioned within the electrolyte solution.
- the electrolyte solution is generally rich in ions to be plated onto the surface of the substrate. Therefore, the application of the electrical bias drives a reductive reaction to reduce the metal ions and precipitate the respective metal. Upon precipitating, the metal plates onto the seed layer to form a film.
- a thick copper layer e.g., >200 ⁇
- a thick copper layer e.g., >200 ⁇
- copper purity is generally questionable due to difficult complete precursor-ligand removal.
- ALD techniques though capable of giving generally conformal deposition with good adhesion to the barrier layer, suffer from very low deposition rates for depositing a continuous copper film on the sidewalls of adequate thickness to serve as a seed layer
- barrier materials such as tantalum or tantalum nitride
- barrier materials such as tantalum or tantalum nitride
- conductive barrier materials e.g., cobalt
- the integrity of the barrier layer may be compromised during the electroplating of a copper layer.
- PVD has been a preferred technique to deposit a copper seed layer and electroless plating techniques for depositing a seed layer onto a barrier layer of tantalum or tantalum nitride are known.
- these techniques have suffered from several problems, such as adhesion failure between the copper seed layer and the barrier layer, as well as the added complexity of a complete electroless deposition system and the associated difficulties of process control.
- adhesion failure between the copper seed layer and the barrier layer
- a well-adhered seed layer has several benefits, such as protecting the barrier layer from the acidic solutions utilized during the electroplating of the bulk copper layer.
- the copper seed supports the subsequently deposited bulk copper and minimizes peeling from the barrier layer.
- the process should deposit the copper seed layer with a strong adhesion to the underlying layer and with good uniformity over the entire substrate surface. Also, the process should be applicable for a range of barrier/adhesion layer materials, including cobalt, tungsten, tungsten nitride, titanium, titanium nitride, Ti—W alloy, tantalum, tantalum nitride, ruthenium, Ru—Ta alloy, rhodium, palladium, osmium, iridium and platinum.
- the barrier or adhesion layer should be maintained with little or no oxidation during seed layer deposition and also should not be chemically reduced during the deposition process. Finally, the process should allow the deposition of a seed layer and a gapfill layer sequentially in the same plating bath.
- the present invention teaches a method for depositing a copper seed layer onto a substrate surface, generally onto a barrier layer or an adhesion layer.
- the barrier or adhesion layer may include a refractory metal and/or a group VIII metal.
- the method includes cathodically pre-treating the substrate surface in an acid-containing solution that is free of copper ions.
- the substrate is then placed into a neutral or alkaline (pH ⁇ 7.0) copper solution that includes complexed copper ions and a current or bias is applied across the substrate surface.
- the complexed copper ions include a carboxylate ligand, such as oxalate or tartrate, or ethylenediamine (ED), EDTA and/or acetate.
- the complexed copper ions are reduced to deposit a copper seed layer onto the barrier or adhesion layer.
- a complex alkaline bath is then used to electrochemically plate a gapfill layer on the substrate surface, followed by overfill in the same bath.
- the ECP deposition of the seed layer, the gap fill layer and the overfill layer may be performed in the same processing chamber.
- an acidic bath ECP gapfill process is performed on the substrate surface, followed by ECP overfill, also in an acidic plating bath.
- the copper plating solutions in all embodiments may also contain one or more additive compounds, including suppressors, levelers, brighteners and stabilizers.
- FIGS. 1A-1C illustrate cross-sectional views of a substrate at different stages of a copper interconnect fabrication sequence.
- FIG. 2 illustrates a copper layer formed on a substrate that may be comprised of multiple copper layers deposited by different electrochemical plating processes.
- FIG. 3 is a graph depicting the relationship of critical current density on a substrate surface during plating versus sulfuric acid concentration in the plating bath.
- FIG. 4 is a top plan view of an electrochemical processing system capable of implementing the methodology of the present invention.
- FIG. 5 illustrates a sectional view of an exemplary plating cell and plating head assembly capable of implementing the methodology of the present invention.
- FIG. 6 is a flow chart of a substrate process sequence for embodiments of the invention.
- the present invention teaches a method for depositing a copper layer onto a substrate surface, generally onto a barrier or adhesion layer.
- the barrier layer may include a refractory metal and/or a group VIII metal.
- group VIII metals e.g., old CAS system notation
- group 8, 9 and 10 elements such as ruthenium (Ru), rhodium (Rh), palladium (Pd), cobalt (Co), nickel (Ni), osmium (Os), iridium (Ir), and platinum (Pt).
- the method includes cathodically pre-treating the substrate surface in an acid-containing solution that is free of copper ions.
- This pre-treatment reduces the critical current density (CCD) required for forming a continuous and void-free seed layer on the barrier or adhesion layer via an ECP process.
- the substrate is then placed into a neutral or alkaline (pH ⁇ 7.0) complex copper solution that includes complexed copper ions and a current or bias is applied across the substrate surface.
- a “complex bath” or “complex solution”, as used herein, is defined as a plating solution containing at least one complexing, or chelating, compound and a metal ion source, wherein the metal ion source comprises the metal to be plated on the substrate, e.g. copper.
- Alkaline as used herein, is defined as pH ⁇ 7.0.
- the complexed copper ions are reduced to deposit a continuous, void-free copper seed layer onto the barrier or adhesion layer.
- a complex alkaline bath is then used to electrochemically plate a gapfill layer onto the seed layer, followed by electrochemical plating of an overfill layer using an acid plating bath.
- the ECP deposition of the seed layer and the gap fill layer may be performed in the same processing chamber and preferably with the same plating solution.
- an acid bath ECP gap fill process is performed on the substrate surface, followed by ECP overfill, also in an acid bath.
- Ruthenium (Ru) thin films can be a potential candidate for a seedless interlayer between intermetal dielectric (IMD) and copper interconnect for ⁇ 45 nm technology.
- Interlayer is defined as a layer deposited between a dielectric layer and a subsequently deposited metal layer. Examples of an interlayer include a copper barrier layer, an adhesion layer, and a combined barrier/adhesion layer.
- Ruthenium is a group VIII metal that has a relatively low electrical resistivity (resistivity ⁇ 7 ⁇ -cm) and high thermal stability (high melting point ⁇ 2300° C.). It is relatively stable even in the presence of oxygen and water at ambient temperature.
- the thermal and electrical conductivities of ruthenium are twice those of Tantalum (Ta). Ruthenium also does not form an alloy with copper below 900° C. and shows good adhesion to copper. Therefore, the semiconductor industry has shown an interest in using Ru as an interlayer layer or adhesion layer.
- the low resistivity of ruthenium can be an advantage when trying to fill ruthenium-coated features with copper without a seed layer.
- ruthenium layers are often very thin (10-100 ⁇ ) and have over three times the electrical resistivity of copper, ruthenium layers still exhibit high sheet resistances, e.g. >20 ohm/square for 100 ⁇ thick ruthenium films.
- the terminal effect associated with trying to plate a material on materials that have a high sheet resistance can make obtaining uniform, void-free copper films on 200 and 300 mm substrates problematic.
- FIGS. 1A-1C illustrate cross-sectional views of a substrate at different stages of a copper interconnect fabrication sequence incorporating a group VIII metal layer.
- FIG. 1A illustrates a cross-sectional view of a substrate 100 having metal contacts 104 and a dielectric layer 102 formed thereon.
- the substrate 100 may comprise a semiconductor material such as, for example, silicon, germanium, or gallium arsenide.
- the dielectric layer 102 may comprise an insulating material such as, silicon dioxide, silicon nitride, silicon oxynitride and/or carbon-doped silicon oxides, such as SiO x C y , for example, BLACK DIAMONDTM low-k dielectric, available from Applied Materials, Inc., located in Santa Clara, Calif.
- the metal contacts 104 may comprise, for example, copper, among others.
- Apertures 120 may be defined in the dielectric layer 102 to provide openings over the metal contacts 104 .
- the apertures 120 may be defined in the dielectric layer 102 using conventional lithography and etching techniques.
- the width of apertures 120 may be as large as about 900 ⁇ and as small as about 400 ⁇ .
- the thickness of dielectric layer 102 could be in the range between about 1000 ⁇ to about 10000 ⁇ .
- a barrier layer 106 may be formed in the apertures 120 defined in the dielectric layer 102 .
- the barrier layer 106 may include one or more refractory metal-containing layers used as a copper-barrier material such as, for example, cobalt, titanium, titanium nitride, titanium silicon nitride, tantalum, tantalum nitride, tantalum silicon nitride, tungsten, tungsten nitride and Ti—W alloy, among others.
- the barrier layer 106 may be formed using a suitable deposition process, such as ALD, chemical vapor deposition (CVD) or physical vapor deposition (PVD).
- the thickness of the barrier layer is between about 5 521 to about 150 ⁇ and preferably less than 100 ⁇ .
- the barrier layer 106 may instead comprise a thin film of group VIII metal, such as ruthenium (Ru), a ruthenium-tantalum alloy, rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt).
- group VIII metal such as ruthenium (Ru), a ruthenium-tantalum alloy, rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt).
- group VIII metal which is resistant to corrosion and oxidation, may provide a surface upon which a copper layer is subsequently deposited using an electrochemical plating (ECP) process.
- ECP electrochemical plating
- the group VIII metal may act as a copper-barrier layer.
- the group VIII metal may be deposited on the conventional barrier layer, such as Ta (tantalum) and/or TaN (tantalum nitride), to serve as an adhesion layer or other interlayer between the conventional barrier layer and subsequently deposited copper layers.
- the group VIII metal is typically deposited using a chemical vapor deposition (CVD) process, atomic layer deposition (ALD) or a physical vapor deposition (PVD) process.
- CVD chemical vapor deposition
- ALD atomic layer deposition
- PVD physical vapor deposition
- a group VIII metal interlayer 108 such as ruthenium (Ru) is formed on the substrate, and in this example on the barrier layer 106 .
- the thickness for the group VIII metal interlayer 108 often depends on the device structure to be fabricated.
- the thickness of the group VIII metal interlayer 108 is less than about 1,000 ⁇ , preferably between about 5 ⁇ to about 200 ⁇ .
- a metal layer e.g., copper layer 110
- a barrier 106 that contains pure tantalum (Ta), or tantalum nitride (TaN)
- One of the problems of plating a metal layer on a pure Ta, or TaN, barrier layer is due to tantalum's high affinity for oxygen, which causes a thermodynamically stable oxide layer to form on the Ta, or TaN, surface, which thus prevents good adhesion between the directly plated metal layer and the Ta, or TaN, barrier layer 106 .
- the adhesion problem is typically found during the direct plating process since the deposited layer easily separates, or de-bonds, from the surface of the barrier layer 106 .
- Conventional processing steps that are adapted to remove the surface oxides on the Ta and TaN, such as aqueous, thermal or plasma processes, which are intended to reduce the formed oxides, are generally ineffective due to rapid re-oxidation of the freshly exposed surfaces.
- a Ru—Ta alloy when used as a group VIII metal interlayer 108 as shown in FIGS. 1A-1C , has the combined benefits of blocking copper diffusion as effectively as conventional tantalum barrier layers and providing a suitable surface for direct plating of a copper seed layer but does not suffer from the same adhesion problems as found with conventional Ta and TaN barrier layers. Therefore, in one aspect of the invention, the barrier layer 106 contains a Ru—Ta alloy that contains between about 70 atomic % and about 95 atomic % of ruthenium and the balance tantalum. In another aspect, the barrier layer preferably contains a Ru—Ta alloy that contains between about 70 atomic % and about 90 atomic % of ruthenium and the balance tantalum.
- the barrier layer more preferably contains a Ru—Ta alloy that contains between about 80 atomic % and about 90 atomic % of ruthenium and the balance tantalum. In one aspect, it may be desirable to select a Ru—Ta alloy that does not contain regions of pure ruthenium and/or pure tantalum on the surface.
- group VIII metal interlayer 108 may also comprise a discontinuous copper layer, for example a very thin ( ⁇ 100 ⁇ ) layer of PVD copper.
- a copper layer may not be electrically conductive, but may provide additional nucleation sites for subsequently deposited copper layers, essentially lowering the effective CCD of the group VIII metal interlayer.
- the apertures 120 may thereafter be filled with copper layer 110 via one or more direct electroplating processes to complete the copper interconnect.
- Direct plating of copper may be performed onto a barrier layer 106 or a group VIII metal interlayer 108 .
- CCD critical current density
- embodiments of the invention contemplate the application of a cathodic pre-treatment process prior to the deposition of copper layer 110 . Critical current density and cathodic pre-treatment are described below in conjunction with FIG. 3 .
- Embodiments of the invention further contemplate different electroplating methods for the deposition of copper layer 110 .
- copper layer 110 may be comprised of multiple copper layers deposited by different electrochemical plating processes. For clarity, layers deposited on the substrate prior to copper deposition, such as dielectric layer 102 , metal contacts 104 , barrier layer 106 and group VIII metal interlayer 108 , are illustrated together in FIG. 2 as conductive substrate surface 114 . Copper layer 110 may include a thin, substantially conformal, continuous, void-free layer, hereinafter referred to as a seed layer 111 , a gap fill layer 112 and an overfill layer 113 .
- a seed layer 110 is electrochemically plated onto conductive substrate surface 114 using a complex alkaline bath and plating process described below in conjunction with FIGS. 3, 5 and 6 .
- Gap fill layer 112 is then electrochemically plated onto seed layer 110 using either a complex alkaline bath gapfill process, described below in conjunction with FIGS. 3, 5 and 6 or a conventional acid bath gapfill process, described below in conjunction with FIGS. 5 and 6 .
- an overfill layer 113 is then deposited onto gap fill layer 112 with an acid bath ECP process, described below in conjunction with FIGS. 5 and 6 .
- An example of an electrochemical plating (ECP) system and an exemplary plating cell are described below in conjunction with FIGS. 4, 5 and 6 .
- Embodiments of the invention contemplate a cathodic pre-treatment of a substrate surface prior to electrochemical plating of copper onto the surface.
- the plating current for a typical ECP process onto a copper seed layer is typically in the range from about 2 mA/cm 2 to about 10 mA/cm 2 for filling copper into submicron trench and/or via structures, such as apertures 120 (shown in FIGS. 1A-1C ).
- a plating current density of 2-10 mA/cm 2 will not provide deposition of a continuous copper film on a ruthenium layer, creating voids.
- a continuous copper film is formed on Ru when the plating current density is increased and/or the electrolyte resistivity is reduced beyond the values used in conventional copper plating.
- a minimum or critical current density, or CCD has been determined wherein plating current densities equal to or above this value will form a thin continuous copper film on a Ru layer and current densities below this value will not form a thin continuous film on the Ru layer.
- the magnitude of the CCD is strongly dependent on the resitivity of the plating solution.
- FIG. 3 illustrates an example of the CCD versus sulfuric acid (H 2 SO 4 ) concentration.
- the CCD as shown in FIG. 3 , is defined as the minimum current density required to form a 1000 ⁇ continuous copper film on a ruthenium surface. Below the CCD, no visually shiny continuous copper film will be deposited at the center regions of the substrate. The magnitude of CCD is shown to strongly depend on the acidity level of the plating bath.
- Over-potential is defined as the difference between the actual potential and the zero-current (open-circuit) potential.
- a high over-potential favors new crystal nucleation by lowering the critical nucleus size and increasing the density of nuclei, while a low electrochemical over-potential favors growth on existing crystallites. Since the plating current density depends on the electrochemical over-potential for a given bath, the copper deposit structure/morphology is therefore affected by the plating current density.
- nucleation is also dependent on the “activity” of the substrate surface, i.e., the concentration of “active sites” on the substrate. Any kind of surface imperfection, such as a crystal dislocation, crystal boundary or incorporated alien atom may serve as the active site. At the same overvoltage, or at the same applied current density, the amount of nuclei formed will be much higher if the barrier layer is free from unwanted deposits, such as ruthenium oxides and some organic compounds, that block the active sites and, hence, inhibit nucleation.
- a substrate with a copper film plated on a 100 ⁇ Ru film in a 10 g/l sulfuric acid containing plating solution with a plating current of 3 mA/cm 2 had large crystallites and poor film deposition in the center region of the substrate. Measured at the edge of the substrate, the thickness of the copper plated film was 1000 ⁇ . According to the results shown in FIG. 3 , the CCD is about 40 mA/cm 2 when the sulfuric acid concentration is 10 g/l. The current density of 3 mA/cm 2 is much lower than the 40 mA/cm 2 CCD shown in FIG. 3 and, as expected, a non-continuous layer was formed.
- a substrate that has a 5000 ⁇ thick continuous copper film can be formed on a 100 ⁇ Ru film (deposited by PVD), using a plating solution containing 60 g/l of H 2 SO 4 and a plating current density of about 10 mA/cm 2 (slightly lower than the CCD of 15 mA/cm 2 ).
- a plating solution containing 60 g/l of H 2 SO 4 and a plating current density of about 10 mA/cm 2 (slightly lower than the CCD of 15 mA/cm 2 ).
- a continuous 1000 ⁇ copper film may be deposited on a 100 ⁇ Ru film on a substrate using a plating bath with a H 2 SO 4 concentration of 160 g/l and a plating current of 5 mA/cm 2 .
- 5 mA/cm 2 is equal to the CCD for this particular acidic concentration.
- cross-section SEM pictures show that voids were formed at the Cu/Ru interface.
- the plating current was raised to 10 mA/cm 2 (2 times CCD of 5 mA/cm 2 ) and the same plating bath was used, a continuous 5000 ⁇ copper film was formed on a 100 ⁇ Ru layer with no voids at the copper/Ru interface.
- Embodiments of the invention contemplate a pre-treatment process that includes a cathodic pre-treatment of the barrier or barrier/adhesion layer, such as barrier layer 106 or group VIII metal interlayer 108 , as shown in FIGS. 1A-1C .
- the cathodic treatment mentioned above is an electrochemical treatment of a substrate surface in a copper-ion-free acid solution.
- An oxidized metallic surface particularly a RuO x surface that has formed on a freshly deposited ruthenium barrier/adhesion layer on a substrate, may be cathodically reduced. Additionally, weakly-bound organic surface contaminants may be expelled from the surface by the cathodic polarization. The removal of these unwanted deposits on the substrate surface prior to electrochemical plating has been demonstrated to reduce the CCD of the barrier/adhesion layer.
- One possible reduction reaction is shown in equation (1): RuO 2 +4H*+4 e ⁇ ⁇ Ru+2H 2 O (1)
- the cathodic treatment may be performed in an electrochemical plating cell similar to the copper plating cell described below in association with FIG. 5 , or in a treatment cell separated from the copper plating system.
- the cathodic treatment cell requires an anode, a cathode and a copper-ion-free acid bath.
- the acidic concentration range should be in the range between about 10 g/l to about 100 g/l, and preferably in the range between about 10 g/l to about 50 g/l.
- a preferred acid is H 2 SO 4 , but other types of acidic solutions, such as organic sulfonic acid solutions (e.g. methylsulfonic acid), may also be used.
- the acidic bath needs to be free of copper ions to prevent copper deposition on the surface during the cathodic treatment. Such deposition would be in the form of poorly nucleated copper islands, leading to poor adhesion and/or voids.
- the cathodic treatment can be realized through potential control or current control.
- a reference electrode is needed to monitor the wafer potential, in addition to the working electrodes, which are the thin as-deposited Ru film on the wafer surface, and an anode.
- Potential control can be realized through a potentiostat.
- the controlled ruthenium electrode potential, with respect to the reference electrode is in the range of about 0 volt to about ⁇ 0.5 volt.
- H 2 evolution may occur on the Ru film surface, hence, it is important to avoid applying a reduction potential to the substrate that is too high.
- a cathodic current will be passed between the substrate, coated with a ruthenium film for example, and an anode.
- the current density should be in the range of about 0.05 mA/cm 2 to about 1 mA/cm 2 .
- the treatment time should be in the range of about 2 seconds to about 30 minutes. However, in the interest of maintaining adequate throughput during large-scale processing of substrates, the treatment is preferably kept below 5 minutes.
- Experimental results have shown that the adhesion is better between copper and a pre-treated, clean, and possibly oxide-free ruthenium surface due to a high-integrity Cu/Ru interface free of voids.
- Good interface integrity between the Cu and the Ru layers can be an important aspect in forming a reliable semiconductor device.
- having a pre-treated ruthenium surface is critical to achieve high quality copper deposition on ruthenium films.
- cathodically pre-treating a ruthenium surface prior to copper plating may improve the substrate surface's hydrophilicity.
- the step coverage of copper plating on substrate features, such as apertures 120 may be improved, since the treated surface is more hydrophilic and, hence, more able to draw the plating solution deep into the features.
- Ru rhodium
- Os osmium
- Ir iridium
- barrier materials such as cobalt, titanium, titanium nitride, titanium silicon nitride, tantalum, tantalum nitride, tantalum silicon nitride, tungsten, tungsten nitride, a Ti—W alloy, and a ruthenium-tantalum alloy.
- Embodiments of the invention teach the use of complexed copper sources contained within an alkaline plating solution for the direct plating of copper layers on barrier and/or barrier/adhesion layers.
- Direct plating is defined as the method of electrochemically plating a more conductive metal layer, such as seed layer 111 in FIG. 2 , onto a substantially less conductive layer, such as conductive substrate surface 114 , to facilitate the subsequent uniform, void-free deposition of a gapfill layer 112 and/or an overfill layer 113 . This process may be performed in a plating cell similar to the electrochemical processing cell described below in conjunction with FIG. 5 .
- a plating solution containing complexed copper sources has a significantly more negative deposition potential than does a plating solution containing free copper ions.
- complexed copper ions have a deposition potential from about ⁇ 1.1 V to about ⁇ 0.5 V, depending on the particular complexing agent.
- Free copper ions have deposition potentials in the range from about ⁇ 0.3 V to about ⁇ 0.1 V, when referenced to Ag/AgCl (1 M KCl), which has a potential of 0.235 V verses a standard hydrogen electrode.
- Suitable plating solutions that may be used with the processes described herein to plate copper may include at least one copper source compound, at least one chelating or complexing compound, optional wetting agents or suppressors, optional pH adjusting agents and a solvent.
- Plating solutions contain at least one copper source compound complexed or chelated with at least one of a variety of ligands.
- Complexed copper includes a copper atom in the nucleus and surrounded by ligands, functional groups, molecules or ions with a strong affinity to the copper, as opposed to free copper ions with very low affinity, if any, to a ligand (e.g., water).
- Complexed copper sources are either chelated before being added to the plating solution or are formed in situ by combining a free copper ion source with a complexing agent.
- the copper atom may be in any oxidation state, such as 0, 1 or 2, before, during or after complexing with a ligand. Therefore, throughout the disclosure, the use of the word copper or elemental symbol Cu includes the use of copper metal (Cu 0 ), cupric (Cu +1 ) or cuprous (Cu +2 ), unless otherwise distinguished or noted.
- copper source compounds include copper citrate, copper ED, copper EDTA, among others.
- a particular copper source compound may have ligated varieties.
- copper citrate may include at least one cupric atom, cuprous atom or combinations thereof and at least one citrate ligand and include Cu(C 6 H 7 O 7 ), Cu 2 (C 6 H 4 O 7 ), Cu 3 (C 6 H 5 O 7 ) or Cu(C 6 H 7 O 7 ) 2 .
- copper EDTA may include at least one cupric atom, cuprous atom or combinations thereof and at least one EDTA ligand and include Cu(C 10 H 15 O 8 N 2 ), Cu 2 (C 10 H 14 O 8 N 2 ), Cu 3 (C 10 H 13 O 8 N 2 ), Cu 4 (C 10 H 12 O 8 N 2 ) or Cu 2 (C 10 H 12 O 8 N 2 ).
- suitable copper source compounds include copper sulfate, copper pyrophosphate and copper fluoroborate.
- the plating solution contains one or more chelating or complexing compounds that include compounds having one or more functional groups selected from the group of carboxylate groups, hydroxyl groups, alkoxyl, oxo acids groups, mixture of hydroxyl and carboxylate groups and combinations thereof.
- suitable chelating compounds include compounds having one or more amine and amide functional groups, such as ethylenediamine (ED), diethylenetriamine, diethylenetriamine derivatives, hexadiamine, amino acids, ethylenediaminetetraacetic acid (EDTA), methylformamide or combinations thereof.
- the plating solution may include one or more chelating agents at a concentration in the range from about 0.02 M to about 1.6 M.
- the one or more chelating compounds may also include salts of the chelating compounds described herein, such as lithium, sodium, potassium, cesium, calcium, magnesium, ammonium and combinations thereof.
- Such salt combines with a copper source to produce NaCu(C 6 H 5 O 7 ).
- suitable inorganic or organic acid salts include ammonium and potassium salts or organic acids, such as ammonium oxalate, ammonium citrate, ammonium succinate, monobasic potassium citrate, dibasic potassium citrate, tribasic potassium citrate, potassium tartrate, ammonium tartrate, potassium succinate, potassium oxalate, and combinations thereof.
- the one or more chelating compounds may also include complexed salts, such as hydrates (e.g., sodium citrate dihydrate).
- Wetting agents or suppressors may be added to the solution in a range from about 10 ppm to about 2,000 ppm, preferably in a range from about 50 ppm to about 1,000 ppm.
- Suppressors include polyacrylamide, polyacrylic acid polymers, polycarboxylate copolymers, polyethers or polyesters of ethylene oxide and/or propylene oxide (EO/PO), coconut diethanolamide, oleic diethanolamide, ethanolamide derivatives or combinations thereof.
- One or more pH-adjusting agents are optionally added to the plating solution to achieve a pH ⁇ 7.0, preferably between about 7.0 and about 9.5.
- the amount of pH adjusting agent can vary as the concentration of the other components is varied in different formulations. Different compounds may provide different pH levels for a given concentration, for example, the composition may include between about 0.1% and about 10% by volume of a base, such as potassium hydroxide, ammonium hydroxide or combinations thereof, to provide the desired pH level.
- the one or more pH adjusting agents may also include acids, including carboxylic acids, such as acetic acid, citric acid, oxalic acid, phosphate-containing components including phosphoric acid, ammonium phosphates, potassium phosphates, inorganic acids, such as sulfuric acid, nitric acid, hydrochloric acid and combinations thereof.
- acids including carboxylic acids, such as acetic acid, citric acid, oxalic acid, phosphate-containing components including phosphoric acid, ammonium phosphates, potassium phosphates, inorganic acids, such as sulfuric acid, nitric acid, hydrochloric acid and combinations thereof.
- a constant cathodic current is applied to the substrate resulting in a constant current density which may be in a range between about 1 mA/cm 2 to about 10 mA/cm 2 for a time period between about 0.1 seconds and 5.0 seconds. This results in the formation of a copper seed layer between about 50 ⁇ and about 300 ⁇ thick on the barrier layer.
- nucleation spike or “nucleation pulse” may be used when the substrate surface is first brought in contact with the plating solution.
- Nucleation spike or “nucleation pulse,” as used herein, is defined as an initial higher plating current level intended to help the nucleation of the copper deposition on the substrate surface, wherein the initial plating current is at least equal to, or ideally greater than, the CCD. This plating current may exceed the maximum plating current that typically allows for bottom-up gapfill of substrate features and therefore is only applied for a short time.
- a constant plating current in the range of about 5 mA/cm 2 to about 20 mA/cm 2 is applied to the barrier layer during the nucleation pulse for about 0.1 to about 5 seconds. This allows the formation of a conformal, uniform and void-free layer on the substrate, such as seed layer 111 , as shown in FIG. 2 .
- aspects of the invention teach the use of a complex alkaline electrolyte for plating a gapfill layer, such as gapfill layer 112 (see FIG. 2 ), onto a seed layer, such as seed layer 111 , that has been directly deposited on a barrier layer via an alkaline solution ECP process.
- This process may be performed in an electrochemical plating cell similar to the electrochemical processing cell described below in conjunction with FIG. 5 .
- This process is similar to that described above for direct plating on a barrier layer with a complex alkaline electrolyte.
- Process parameters are believed to enhance the bottom-up gapfill process, however, including plating current and deposition time. Generally, higher deposition rates and, hence, plating current densities, may be utilized for this process.
- the bath used for this process is also similar to that used for direct plating.
- the complex alkaline bath for gapfill contains at least one copper source compound and at least one complexing compounds, as detailed previously.
- the one or more complexing compounds may also include salts of the chelating compounds, listed above.
- the bath also may contain wetting agents and one or more pH-adjusting agents (see above). Concentrations of the bath's components are believed to enhance the bottom-up gapfill process.
- nucleation pulse is unnecessary for the formation of a uniform, void-free metal layer to be formed on the seed layer.
- aspects of the invention teach the use of a conventional acid electrolyte for plating a gap fill layer onto a seed layer that has been directly deposited on a barrier layer via an alkaline solution ECP process.
- ECP gapfill deposition of copper onto a copper seed layer using an acidic plating solution is well known in the art and may be performed in an electrochemical plating cell similar to the copper plating cell described below in conjunction with FIGS. 4 and 5 .
- This process may also be used for depositing a copper overfill layer on a substrate, such as overfill layer 113 , in FIG. 2 .
- a conventional, i.e., non-complex, electrochemical plating solution for ECP generally includes a copper source, an acid source, a chlorine ion source, and at least one plating solution additive, i.e., levelers, suppressors, accelerators, antifoaming agents, etc.
- the plating solution may contain between about 30 g/l and about 60 g/l of copper, between about 10 g/l to about 50 g/l of sulfuric acid, between about 20 and about 100 ppm of chlorine ions, between about 5 and about 30 ppm of an additive accelerator, between about 100 and about 1000 ppm of an additive suppressor, and between about 1 and about 6 ml/l of an additive leveler.
- the plating current may be in the range from about 2 mA/cm 2 to about 10 mA/cm 2 for filling about 300 ⁇ to about 3000 ⁇ copper into the submicron trench and/or via structure.
- a substantially similar process is used for an overfill plating process, in which an additional 5000 ⁇ to 10,000 ⁇ of copper is plated on to a substrate to complete a copper interconnect layer.
- Examples of copper plating chemistries and processes can be found in commonly assigned U.S. patent application Ser. No. 10/616,097, titled “Multiple-Step Electrodeposition Process For Direct Copper Plating On Barrier Metals”, filed on Jul. 8, 2003, and U.S. patent application NO. 60/510,190, titled “Methods And Chemistry For Providing Initial Conformal Electrochemical Deposition Of Copper In Sub-Micron Features”, filed on Oct. 10, 2003.
- FIG. 4 is a top plan view of an embodiment of an electrochemical processing system (ECPS) 400 capable of implementing the methodology of the present invention.
- the ECPS 400 generally includes a processing base 413 having a robot 420 centrally positioned thereon.
- the robot 420 generally includes one or more robot arms 422 and 424 configured to support substrates thereon. Additionally, the robot 420 and the robot arms 422 and 424 are generally configured to extend, rotate and vertically move so that the robot 420 may insert and remove substrates to and from a plurality of processing locations 402 , 404 , 406 , 408 , 410 , 412 , 414 and 416 positioned on the base 413 .
- Processing locations may be configured as electroless plating cells, electrochemical processing cells, substrate rinsing and/or drying cells, substrate bevel clean cells, substrate surface clean or preclean cells and/or other processing cells that are advantageous to plating processes.
- embodiments of the present invention are conducted within at least one of the processing locations 402 , 404 , 406 , 408 , 410 and 412 .
- the ECPS 400 further includes a factory interface, or FI 430 .
- the FI 430 generally includes at least one FI robot 432 positioned adjacent one side of the FI 430 that is adjacent to the processing base 413 .
- the FI robot 432 is positioned to access a substrate 426 from substrate cassettes 434 .
- the FI robot 432 delivers the substrate 426 to one of processing locations 414 and 416 to initiate a processing sequence.
- FI robot 432 may be used to retrieve substrates from one of the processing locations 414 and 416 after a substrate processing sequence is complete. In this situation FI robot 432 may deliver the substrate 426 back to one of the cassettes 434 for removal from the system 400 .
- robot 432 also extends into a link tunnel 415 that connects factory interface 430 to processing mainframe or platform 413 .
- FI robot 432 is configured to access an anneal chamber 435 positioned in communication with the FI 430 .
- FIG. 5 illustrates a partial perspective and sectional view of an exemplary electrochemical processing cell, hereinafter referred to as plating cell 500 , that may be implemented in processing locations 402 , 404 , 406 , 408 , 410 , 412 , 414 , 416 of FIG. 4 .
- the plating cell 500 generally includes a plating head assembly 600 , a frame member 503 , an outer basin 501 and an inner basin 502 positioned within outer basin 501 .
- the plating head assembly 600 includes a receiving member 601 for supporting and rotating a substrate during immersion into the electrochemical processing solution and during electrochemical processing.
- receiving member 601 includes a contact ring 602 and a thrust plate assembly 604 that are separated by a loading space 606 .
- the contact ring 602 may be adapted to make electrical contact around the periphery of the substrate so that the necessary electrical bias may be applied to the substrate.
- the contact ring 602 may be further adapted to include a reference electrode that is located close to the substrate surface.
- a more detailed description of the contact ring 602 and thrust plate assembly 604 may be found in commonly assigned U.S.
- the frame member 503 of plating cell 500 supports an annular base member 504 on an upper portion thereof. Since frame member 503 is elevated on one side, the upper surface of base member 504 is generally tilted from the horizontal at an angle that corresponds to the tilt angle of frame member 503 relative to a horizontal position.
- Base member 504 includes a disk-shaped anode 505 .
- Plating cell 500 may be positioned at a tilt angle, i.e., the frame portion 503 of plating cell 500 may be elevated on one side such that the components of plating cell 500 are tilted between about 3° and about 30°.
- Inner basin 502 is generally configured to contain a processing solution, such as a plating solution or a cathodic pre-treatment solution, during electrochemical processing of substrates.
- a processing solution such as a plating solution or a cathodic pre-treatment solution
- the processing solution is generally continuously supplied to inner basin 502 , and therefore, the processing solution continually overflows the uppermost point 502 a, generally termed a “weir”, of inner basin 502 and is collected by outer basin 501 and drained therefrom for chemical management and recirculation.
- the exemplary electrochemical processing cell is further illustrated in commonly assigned U.S. patent application Ser. No. 10/268,284, filed on Oct. 9, 2002, and entitled “Electrochemical Processing Cell”, claiming priority to U.S. Provisional Application Ser. No. 60/398,345, which was filed on Jul. 24, 2002, both of which are incorporated herein by reference in their entireties.
- a substrate may be transferred into an electrochemical processing cell, such as plating cell 500 for example, and positioned face-down on contact ring 602 .
- Thrust plate assembly 604 holds the substrate in place during processing.
- the substrate is then immersed in the electrolyte solution filling inner basin 502 , typically while being rotated by the contact ring 602 between about 5 rpm and about 60 rpm.
- the electrolyte solution may comprise an acidic, copper free solution, a complexed-copper alkaline solution, or a conventional acidic copper-containing solution, depending on the process being performed on the substrate.
- the substrate may be rotated between about 10 rpm and about 100 rpm during processing step by contact ring 602 .
- the time required for processing is dependent on each particular process, such as cathodic pre-treatment, seed layer deposition, seed layer and gapfill layer deposition, etc.
- the bias is then removed and the substrate is positioned above the electrolyte solution and uppermost point 502 a of inner basin 502 for removal from plating cell 500 .
- the substrate Prior to removal from plating cell 500 , the substrate may be rotated between about 100 and 1000 rpm for between about 1 second and about 10 seconds in order to remove excess solution from the substrate.
- FIG. 6 is a flow chart of a substrate process sequence 610 .
- Embodiments include a method for depositing a metal layer onto a barrier and/or adhesion layer on a substrate that includes:
- a cathodic pre-treatment 611 of the barrier or adhesion layer in an acid-containing bath is provided.
- Gapfill layer deposition 613 of a gapfill layer on the seed layer is Gapfill layer deposition 613 of a gapfill layer on the seed layer.
- a cathodic pre-treatment 611 of a substrate surface is performed.
- the cathodic pre-treatment 611 may reduce the critical current density required to form a uniform, void-free, conformal metal layer on a barrier layer.
- seed layer deposition 612 takes place on the substrate, wherein a seed layer, such as seed layer 111 in FIG. 2 , is directly plated onto conductive substrate surface 114 using an electrochemical process with a complex alkaline bath.
- a nucleation pulse is used to improve the quality of the seed layer.
- the cathodic pre-treatment 611 and seed layer deposition 612 are performed on the same electrochemical processing system, such as ECPS 400, described above in conjunction with FIG. 4 , reducing the exposure time of the cathodically treated surface to oxygen and ambient contamination to minutes or even seconds. This minimizes the formation of unwanted deposits on the treated barrier layer surface prior to seed layer deposition.
- Gapfill layer deposition 613 then takes place on the substrate, wherein a gapfill layer, such as gapfill layer 112 in FIG. 2 , is plated onto seed layer 111 using the electrochemical gapfill process with a complex alkaline bath described above.
- the seed layer deposition 612 and the gapfill layer deposition 613 are performed sequentially in the same plating cell using the same plating solution. This is especially useful for gapfill of interconnect features smaller than 65 nm; such small interconnect features are particularly sensitive to the formation of voids during gapfill as well as the presence of unwanted deposits at the interface between the seed layer and the gapfill layer.
- the surface of the seed layer is never exposed to atmosphere prior to gapfill layer deposition 613 , eliminating the possibility of unwanted oxidation. Further, there is virtually no time for organic contaminants to accumulate on the seed layer surface since the seed layer deposition 612 may be followed immediately by the gapfill layer deposition 613 .
- An overfill deposition 614 then may be performed on the substrate, wherein an ECP overfill layer, such as overfill layer 113 , may be deposited to complete formation of an interconnect layer.
- the overfill deposition 614 is performed sequentially in the same plating cell as gapfill deposition 613 , using the same plating solution. This avoids oxidation and organic contamination of the gapfill layer prior to overfill deposition 614 .
- the overfill deposition 614 is performed via a conventional acidic electrolyte ECP process.
- an additional rinsing step is performed on the substrate between the gapfill layer deposition 613 and the overfill deposition 614 to prevent cross-contamination of the plating solution used for ECP overfill.
- the additional rinsing step may be performed in a dedicated rinsing chamber, preferably located on the same electrochemical processing system wherein the substrate process sequence 610 may be performed.
- the substrate is rinsed with an aqueous solution while rotating at a rate from about 20 to about 400 rpm and subsequently dried via gas flow and/or spin-drying. Due to the inherent incompatibility of acidic and basic solutions, as well as the serious problems associated with cross-contamination of organic additives between plating solutions, rigorous cleaning of the plating cell would have to be performed between the gapfill layer deposition 613 and the overfill deposition 614 for each substrate processed therein.
- both ECP cells are preferably situated on the same substrate processing platform, such as the exemplary plating system described below in conjunction with FIG. 4 .
- the overfill deposition 614 is particularly beneficial when there is a need to fill large and small interconnect features on a substrate surface at the same time; the small or high aspect ratio interconnect features are filled during the gapfill layer deposition 613 and the larger, low aspect ratio features are filled with the higher deposition rate ECP overfill process.
- a cathodic pre-treatment 611 is performed on a substrate surface, such as conductive substrate surface 114 in FIG. 2 . As stated above in the previous embodiment, the cathodic pre-treatment 611 reduces the critical current density.
- the seed layer deposition 612 takes place on the substrate, wherein a seed layer is directly plated onto conductive substrate surface 114 using an electrochemical process with a complex alkaline bath.
- a nucleation pulse is used to improve the quality of the seed layer.
- the cathodic pre-treatment 611 and the seed layer deposition 612 are performed on the same electrochemical processing system.
- the smallest interconnect features on a substrate are completely filled during the seed layer deposition 612 , whereas only a conformal seed layer is formed on the surfaces of larger interconnect features.
- the cathodic pre-treatment 611 and the seed layer deposition 612 are performed on the same electrochemical processing system to minimize the formation of unwanted deposits on the treated barrier layer surface prior to seed layer deposition.
- gapfill layer deposition 613 a gapfill layer is plated onto seed layer 111 using an electrochemical gapfill process with a conventional acid bath as described above. No complexing agents are necessary in this plating process.
- gapfill layer deposition 613 is performed in a different electrochemical processing cell than the seed layer deposition 612 to isolate acid-based and alkaline-based processes.
- an additional rinsing step is performed on the substrate between the seed layer deposition 612 and the gapfill deposition 613 to prevent cross-contamination of the plating solution used for gapfill.
- the additional rinsing step is substantially similar to that described above in overfill deposition 614 of the previous embodiment.
- overfill deposition 614 an ECP overfill layer may be deposited to complete formation of an interconnect layer.
- overfill deposition 614 is performed via a conventional acidic electrolyte ECP process.
- Overfill deposition 614 may be performed in the same electrochemical processing cell as gapfill layer deposition 613 to prevent oxidation and other surface contaminants form forming at the interface between the gapfill layer and the overfill layer.
- overfill deposition 614 is performed on the same electrochemical processing system as gapfill layer deposition 613 , but in a different electrochemical processing cell.
- This embodiment allows for gapfill of the smallest features on a substrate during cathodic pre-treatment 611 , wherein the seed layer is deposited for larger interconnect features. Subsequently, gapfill of the larger features as well as overfill deposition of the interconnect layer may be performed on a substrate in a single ECP cell. This method increases the productivity of electrochemical processing systems by combining two process steps into a single plating cell.
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Abstract
The present invention teaches a method for depositing a copper seed layer onto a substrate surface, generally onto a barrier layer. The barrier layer may include a refractory metal and/or a group 8, 9 or 10 metal. The method includes cathodically pre-treating the substrate in an acid-containing solution. The substrate is then placed into a copper solution (pH≧7.0) that includes complexed copper ions and a current or bias is applied across the substrate surface. The complexed copper ions are reduced to deposit a copper seed layer onto the barrier layer. In one aspect, a complex alkaline bath is then used to electrochemically plate a gapfill layer on the substrate surface, followed by overfill in the same bath. In another aspect, an acidic bath ECP gapfill process and overfill process follow the alkaline seed layer process.
Description
- This application claims benefit of U.S. provisional patent application Ser. No. 60/621,173 [APPM 9762L], filed Oct. 21, 2004, which is herein incorporated by reference.
- This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 11/007,857 [APPM 9200], filed Dec. 9, 2004, which claims benefit of U.S. Provisional Patent Application Ser. No. 60/579,129, filed Jun. 10, 2004. This application is also a continuation-in-part of co-pending U.S. patent application Ser. No. 11/012,965 [APPM 9201], filed Dec. 15, 2004, which claims benefit of U.S. Provisional Patent Application Ser. No. 60/579,129, filed Jun. 10, 2004, and U.S. Provisional Patent Application Ser. No. 60/621,215, filed Oct. 21, 2004. This application is also a continuation-in-part of co-pending U.S. patent application Ser. No. 10/616,097 [APPM 8241], filed Jul. 8, 2003. Each of the aforementioned related patent applications is herein incorporated by reference.
- 1. Field of the Invention
- Embodiments of the present invention generally relate to a method to deposit a metal layer with electrochemical plating and more particularly, to the direct plating of a copper layer onto a barrier or adhesion layer.
- 2. Description of the Related Art
- Metallization for sub-quarter micron sized features is a foundational technology for present and future generations of integrated circuit manufacturing processes. In devices such as ultra large scale integration-type devices, i.e., devices having integrated circuits with more than a million logic gates, the multilevel interconnects that lie at the heart of these devices are generally formed by filling high aspect ratio interconnect features with a conductive material (e.g., copper or aluminum). Conventionally, deposition techniques such as chemical vapor deposition (CVD) and physical vapor deposition (PVD) have been used to fill these interconnect features. However, as interconnect sizes decrease and aspect ratios of device features increase, void-free filling of interconnect features via conventional metallization techniques becomes increasingly difficult. As a result, plating techniques, such as electrochemical plating (ECP) and electroless plating have emerged as viable processes for filling sub-quarter micron sized, high aspect ratio interconnect features in integrated circuit manufacturing processes.
- In an ECP process, sub-quarter micron sized high aspect ratio features formed into the surface of a substrate may be efficiently filled with a conductive material, such as copper. Most ECP processes are generally two stage processes, wherein a seed layer is first formed over the surface features of the substrate (this process may be performed in a separate system), and then the substrate surface features are exposed to an electrolyte solution while an electrical bias is simultaneously applied between the substrate and an anode positioned within the electrolyte solution. The electrolyte solution is generally rich in ions to be plated onto the surface of the substrate. Therefore, the application of the electrical bias drives a reductive reaction to reduce the metal ions and precipitate the respective metal. Upon precipitating, the metal plates onto the seed layer to form a film.
- The process requirements for copper interconnects are becoming more stringent, as the critical dimensions for modern microelectronic devices shrink to 0.1 μm or less. As a result thereof, conventional plating processes will likely be inadequate to support the demands of future interconnect technologies. Conventional plating practices include depositing a copper seed layer via physical vapor deposition (PVD), chemical vapor deposition (CVD) or atomic layer deposition (ALD) onto a diffusion barrier layer (e.g., tantalum or tantalum nitride). However, it is extremely difficult to have adequate seed step coverage with PVD techniques, as discontinuous islands of copper agglomerates are often obtained close to the feature bottom in high aspect ratio features with PVD techniques. For PVD techniques, a thick copper layer (e.g., >200 Å) over the field is generally needed to have continuous sidewall coverage throughout the depth of the features, which often causes the throat of the feature to close before the feature sidewalls are covered. For CVD processes, copper purity is generally questionable due to difficult complete precursor-ligand removal. ALD techniques, though capable of giving generally conformal deposition with good adhesion to the barrier layer, suffer from very low deposition rates for depositing a continuous copper film on the sidewalls of adequate thickness to serve as a seed layer
- Direct electroplating on barrier materials, such as tantalum or tantalum nitride, is difficult, since these traditional barrier materials generally have insulating native oxides across the surface. Also during electroplating, conductive barrier materials (e.g., cobalt) generally will oxidize near the reductive potential of free copper ions. Therefore, the integrity of the barrier layer may be compromised during the electroplating of a copper layer.
- PVD has been a preferred technique to deposit a copper seed layer and electroless plating techniques for depositing a seed layer onto a barrier layer of tantalum or tantalum nitride are known. However, these techniques have suffered from several problems, such as adhesion failure between the copper seed layer and the barrier layer, as well as the added complexity of a complete electroless deposition system and the associated difficulties of process control. In addition, for interconnect features as small as 32 to 45 nm, it is beneficial to perform the seed layer deposition and the gapfill deposition uninterrupted to prevent formation of oxide or other contamination of the seed layer. Furthermore, a well-adhered seed layer has several benefits, such as protecting the barrier layer from the acidic solutions utilized during the electroplating of the bulk copper layer. Also, the copper seed supports the subsequently deposited bulk copper and minimizes peeling from the barrier layer.
- Therefore, there is a need for a process for depositing a copper seed layer onto a barrier or adhesion layer. The process should deposit the copper seed layer with a strong adhesion to the underlying layer and with good uniformity over the entire substrate surface. Also, the process should be applicable for a range of barrier/adhesion layer materials, including cobalt, tungsten, tungsten nitride, titanium, titanium nitride, Ti—W alloy, tantalum, tantalum nitride, ruthenium, Ru—Ta alloy, rhodium, palladium, osmium, iridium and platinum. Further, the barrier or adhesion layer should be maintained with little or no oxidation during seed layer deposition and also should not be chemically reduced during the deposition process. Finally, the process should allow the deposition of a seed layer and a gapfill layer sequentially in the same plating bath.
- The present invention teaches a method for depositing a copper seed layer onto a substrate surface, generally onto a barrier layer or an adhesion layer. The barrier or adhesion layer may include a refractory metal and/or a group VIII metal. The method includes cathodically pre-treating the substrate surface in an acid-containing solution that is free of copper ions. The substrate is then placed into a neutral or alkaline (pH≧7.0) copper solution that includes complexed copper ions and a current or bias is applied across the substrate surface. The complexed copper ions include a carboxylate ligand, such as oxalate or tartrate, or ethylenediamine (ED), EDTA and/or acetate. The complexed copper ions are reduced to deposit a copper seed layer onto the barrier or adhesion layer. In one aspect, a complex alkaline bath is then used to electrochemically plate a gapfill layer on the substrate surface, followed by overfill in the same bath. In this aspect, the ECP deposition of the seed layer, the gap fill layer and the overfill layer may be performed in the same processing chamber. In another aspect, an acidic bath ECP gapfill process is performed on the substrate surface, followed by ECP overfill, also in an acidic plating bath. The copper plating solutions in all embodiments may also contain one or more additive compounds, including suppressors, levelers, brighteners and stabilizers.
- So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
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FIGS. 1A-1C illustrate cross-sectional views of a substrate at different stages of a copper interconnect fabrication sequence. -
FIG. 2 illustrates a copper layer formed on a substrate that may be comprised of multiple copper layers deposited by different electrochemical plating processes. -
FIG. 3 is a graph depicting the relationship of critical current density on a substrate surface during plating versus sulfuric acid concentration in the plating bath. -
FIG. 4 is a top plan view of an electrochemical processing system capable of implementing the methodology of the present invention. -
FIG. 5 illustrates a sectional view of an exemplary plating cell and plating head assembly capable of implementing the methodology of the present invention. -
FIG. 6 is a flow chart of a substrate process sequence for embodiments of the invention. - For clarity, identical reference numerals have been used, where applicable, to designate identical elements that are common between figures.
- The present invention teaches a method for depositing a copper layer onto a substrate surface, generally onto a barrier or adhesion layer. The barrier layer may include a refractory metal and/or a group VIII metal. The term group VIII metals (e.g., old CAS system notation) is generally intended to describe
group 8, 9 and 10 elements, such as ruthenium (Ru), rhodium (Rh), palladium (Pd), cobalt (Co), nickel (Ni), osmium (Os), iridium (Ir), and platinum (Pt). The method includes cathodically pre-treating the substrate surface in an acid-containing solution that is free of copper ions. This pre-treatment reduces the critical current density (CCD) required for forming a continuous and void-free seed layer on the barrier or adhesion layer via an ECP process. The substrate is then placed into a neutral or alkaline (pH≧7.0) complex copper solution that includes complexed copper ions and a current or bias is applied across the substrate surface. A “complex bath” or “complex solution”, as used herein, is defined as a plating solution containing at least one complexing, or chelating, compound and a metal ion source, wherein the metal ion source comprises the metal to be plated on the substrate, e.g. copper. “Alkaline,” as used herein, is defined as pH≧7.0. The complexed copper ions are reduced to deposit a continuous, void-free copper seed layer onto the barrier or adhesion layer. In one aspect, a complex alkaline bath is then used to electrochemically plate a gapfill layer onto the seed layer, followed by electrochemical plating of an overfill layer using an acid plating bath. In this aspect, the ECP deposition of the seed layer and the gap fill layer may be performed in the same processing chamber and preferably with the same plating solution. In another aspect, an acid bath ECP gap fill process is performed on the substrate surface, followed by ECP overfill, also in an acid bath. - Ruthenium (Ru) thin films, deposited by CVD, ALD or PVD, can be a potential candidate for a seedless interlayer between intermetal dielectric (IMD) and copper interconnect for ≦45 nm technology. “Interlayer”, as used herein, is defined as a layer deposited between a dielectric layer and a subsequently deposited metal layer. Examples of an interlayer include a copper barrier layer, an adhesion layer, and a combined barrier/adhesion layer. Ruthenium is a group VIII metal that has a relatively low electrical resistivity (resistivity ˜7 μΩ-cm) and high thermal stability (high melting point ˜2300° C.). It is relatively stable even in the presence of oxygen and water at ambient temperature. The thermal and electrical conductivities of ruthenium are twice those of Tantalum (Ta). Ruthenium also does not form an alloy with copper below 900° C. and shows good adhesion to copper. Therefore, the semiconductor industry has shown an interest in using Ru as an interlayer layer or adhesion layer. The low resistivity of ruthenium can be an advantage when trying to fill ruthenium-coated features with copper without a seed layer. However, because ruthenium layers are often very thin (10-100 Å) and have over three times the electrical resistivity of copper, ruthenium layers still exhibit high sheet resistances, e.g. >20 ohm/square for 100 Å thick ruthenium films. The terminal effect associated with trying to plate a material on materials that have a high sheet resistance can make obtaining uniform, void-free copper films on 200 and 300 mm substrates problematic.
-
FIGS. 1A-1C illustrate cross-sectional views of a substrate at different stages of a copper interconnect fabrication sequence incorporating a group VIII metal layer.FIG. 1A illustrates a cross-sectional view of asubstrate 100 havingmetal contacts 104 and adielectric layer 102 formed thereon. Thesubstrate 100 may comprise a semiconductor material such as, for example, silicon, germanium, or gallium arsenide. Thedielectric layer 102 may comprise an insulating material such as, silicon dioxide, silicon nitride, silicon oxynitride and/or carbon-doped silicon oxides, such as SiOxCy, for example, BLACK DIAMOND™ low-k dielectric, available from Applied Materials, Inc., located in Santa Clara, Calif. Themetal contacts 104 may comprise, for example, copper, among others.Apertures 120 may be defined in thedielectric layer 102 to provide openings over themetal contacts 104. Theapertures 120 may be defined in thedielectric layer 102 using conventional lithography and etching techniques. The width ofapertures 120 may be as large as about 900 Å and as small as about 400 Å. The thickness ofdielectric layer 102 could be in the range between about 1000 Å to about 10000 Å. - A
barrier layer 106 may be formed in theapertures 120 defined in thedielectric layer 102. Thebarrier layer 106 may include one or more refractory metal-containing layers used as a copper-barrier material such as, for example, cobalt, titanium, titanium nitride, titanium silicon nitride, tantalum, tantalum nitride, tantalum silicon nitride, tungsten, tungsten nitride and Ti—W alloy, among others. Thebarrier layer 106 may be formed using a suitable deposition process, such as ALD, chemical vapor deposition (CVD) or physical vapor deposition (PVD). The thickness of the barrier layer is between about 5 521 to about 150 Å and preferably less than 100 Å. - As noted above, the
barrier layer 106 may instead comprise a thin film of group VIII metal, such as ruthenium (Ru), a ruthenium-tantalum alloy, rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt). Such group VIII metal, which is resistant to corrosion and oxidation, may provide a surface upon which a copper layer is subsequently deposited using an electrochemical plating (ECP) process. The group VIII metal may act as a copper-barrier layer. Alternately, the group VIII metal may be deposited on the conventional barrier layer, such as Ta (tantalum) and/or TaN (tantalum nitride), to serve as an adhesion layer or other interlayer between the conventional barrier layer and subsequently deposited copper layers. The group VIII metal is typically deposited using a chemical vapor deposition (CVD) process, atomic layer deposition (ALD) or a physical vapor deposition (PVD) process. Referring toFIG. 1B , a groupVIII metal interlayer 108, such as ruthenium (Ru), is formed on the substrate, and in this example on thebarrier layer 106. The thickness for the groupVIII metal interlayer 108 often depends on the device structure to be fabricated. Typically, the thickness of the groupVIII metal interlayer 108, such as ruthenium, is less than about 1,000 Å, preferably between about 5 Å to about 200 Å. - It has been found that the process of directly plating a metal layer (e.g., copper layer 110) on a
barrier 106 that contains pure tantalum (Ta), or tantalum nitride (TaN), will not give good process results. One of the problems of plating a metal layer on a pure Ta, or TaN, barrier layer is due to tantalum's high affinity for oxygen, which causes a thermodynamically stable oxide layer to form on the Ta, or TaN, surface, which thus prevents good adhesion between the directly plated metal layer and the Ta, or TaN,barrier layer 106. The adhesion problem is typically found during the direct plating process since the deposited layer easily separates, or de-bonds, from the surface of thebarrier layer 106. Conventional processing steps that are adapted to remove the surface oxides on the Ta and TaN, such as aqueous, thermal or plasma processes, which are intended to reduce the formed oxides, are generally ineffective due to rapid re-oxidation of the freshly exposed surfaces. - A Ru—Ta alloy, when used as a group
VIII metal interlayer 108 as shown inFIGS. 1A-1C , has the combined benefits of blocking copper diffusion as effectively as conventional tantalum barrier layers and providing a suitable surface for direct plating of a copper seed layer but does not suffer from the same adhesion problems as found with conventional Ta and TaN barrier layers. Therefore, in one aspect of the invention, thebarrier layer 106 contains a Ru—Ta alloy that contains between about 70 atomic % and about 95 atomic % of ruthenium and the balance tantalum. In another aspect, the barrier layer preferably contains a Ru—Ta alloy that contains between about 70 atomic % and about 90 atomic % of ruthenium and the balance tantalum. In yet another aspect, the barrier layer more preferably contains a Ru—Ta alloy that contains between about 80 atomic % and about 90 atomic % of ruthenium and the balance tantalum. In one aspect, it may be desirable to select a Ru—Ta alloy that does not contain regions of pure ruthenium and/or pure tantalum on the surface. - In some cases, group
VIII metal interlayer 108 may also comprise a discontinuous copper layer, for example a very thin (<100 Å) layer of PVD copper. Such a copper layer may not be electrically conductive, but may provide additional nucleation sites for subsequently deposited copper layers, essentially lowering the effective CCD of the group VIII metal interlayer. - Referring to
FIG. 1C , theapertures 120 may thereafter be filled withcopper layer 110 via one or more direct electroplating processes to complete the copper interconnect. Direct plating of copper may be performed onto abarrier layer 106 or a groupVIII metal interlayer 108. However, because it may be beneficial to reduce the critical current density (CCD) required to plate copper onto the substrate surface, i.e. ontobarrier layer 106 or groupVIII metal interlayer 108, embodiments of the invention contemplate the application of a cathodic pre-treatment process prior to the deposition ofcopper layer 110. Critical current density and cathodic pre-treatment are described below in conjunction withFIG. 3 . Embodiments of the invention further contemplate different electroplating methods for the deposition ofcopper layer 110. - Referring to
FIG. 2 ,copper layer 110 may be comprised of multiple copper layers deposited by different electrochemical plating processes. For clarity, layers deposited on the substrate prior to copper deposition, such asdielectric layer 102,metal contacts 104,barrier layer 106 and groupVIII metal interlayer 108, are illustrated together inFIG. 2 asconductive substrate surface 114.Copper layer 110 may include a thin, substantially conformal, continuous, void-free layer, hereinafter referred to as aseed layer 111, agap fill layer 112 and anoverfill layer 113. - In one embodiment, after cathodic pre-treatment of the substrate surface, a
seed layer 110 is electrochemically plated ontoconductive substrate surface 114 using a complex alkaline bath and plating process described below in conjunction withFIGS. 3, 5 and 6.Gap fill layer 112 is then electrochemically plated ontoseed layer 110 using either a complex alkaline bath gapfill process, described below in conjunction withFIGS. 3, 5 and 6 or a conventional acid bath gapfill process, described below in conjunction withFIGS. 5 and 6 . In one aspect, anoverfill layer 113 is then deposited ontogap fill layer 112 with an acid bath ECP process, described below in conjunction withFIGS. 5 and 6 . An example of an electrochemical plating (ECP) system and an exemplary plating cell are described below in conjunction withFIGS. 4, 5 and 6. - Electrochemical Processes
- Cathodic Pre-Treatment of Barrier Layer
- Embodiments of the invention contemplate a cathodic pre-treatment of a substrate surface prior to electrochemical plating of copper onto the surface.
- The plating current for a typical ECP process onto a copper seed layer is typically in the range from about 2 mA/cm2 to about 10 mA/cm2 for filling copper into submicron trench and/or via structures, such as apertures 120 (shown in
FIGS. 1A-1C ). However, it has been found that a plating current density of 2-10 mA/cm2 will not provide deposition of a continuous copper film on a ruthenium layer, creating voids. A continuous copper film is formed on Ru when the plating current density is increased and/or the electrolyte resistivity is reduced beyond the values used in conventional copper plating. A minimum or critical current density, or CCD, has been determined wherein plating current densities equal to or above this value will form a thin continuous copper film on a Ru layer and current densities below this value will not form a thin continuous film on the Ru layer. The magnitude of the CCD is strongly dependent on the resitivity of the plating solution. -
FIG. 3 illustrates an example of the CCD versus sulfuric acid (H2SO4) concentration. The CCD, as shown inFIG. 3 , is defined as the minimum current density required to form a 1000 Å continuous copper film on a ruthenium surface. Below the CCD, no visually shiny continuous copper film will be deposited at the center regions of the substrate. The magnitude of CCD is shown to strongly depend on the acidity level of the plating bath. - It is well known that the kinetics of nucleation and crystal growth for electro-deposition is intimately related to the local electrochemical over-potential at the nucleation/growth sites as well as the condition of the surface whereon crystal growth takes place. Over-potential is defined as the difference between the actual potential and the zero-current (open-circuit) potential. A high over-potential favors new crystal nucleation by lowering the critical nucleus size and increasing the density of nuclei, while a low electrochemical over-potential favors growth on existing crystallites. Since the plating current density depends on the electrochemical over-potential for a given bath, the copper deposit structure/morphology is therefore affected by the plating current density. Further, nucleation is also dependent on the “activity” of the substrate surface, i.e., the concentration of “active sites” on the substrate. Any kind of surface imperfection, such as a crystal dislocation, crystal boundary or incorporated alien atom may serve as the active site. At the same overvoltage, or at the same applied current density, the amount of nuclei formed will be much higher if the barrier layer is free from unwanted deposits, such as ruthenium oxides and some organic compounds, that block the active sites and, hence, inhibit nucleation.
- As predicted by theory and confirmed by scanning electron microscopic (SEM) images, a substrate with a copper film plated on a 100 Å Ru film in a 10 g/l sulfuric acid containing plating solution with a plating current of 3 mA/cm2 had large crystallites and poor film deposition in the center region of the substrate. Measured at the edge of the substrate, the thickness of the copper plated film was 1000 Å. According to the results shown in
FIG. 3 , the CCD is about 40 mA/cm2 when the sulfuric acid concentration is 10 g/l. The current density of 3 mA/cm2 is much lower than the 40 mA/cm2 CCD shown inFIG. 3 and, as expected, a non-continuous layer was formed. It is believed that under this plating condition, only a few crystallites are stable enough to serve as the nucleation center for further crystal growth, and thus the energy from the plating current is primarily used in growing these crystals, with the help of fast copper adatom surface diffusion. Therefore, the SEM shows large crystallites and copper island deposition in the center region of the substrate. To form a continuous copper film across the entire substrate under this condition, the deposited layer would have to be very thick and the deposited layer would likely contain voids, which would make it unsuitable for Cu interconnect applications. Such poor deposition has been found even when the plating current density is only slightly lower than the CCD. For example, a substrate that has a 5000 Å thick continuous copper film can be formed on a 100 Å Ru film (deposited by PVD), using a plating solution containing 60 g/l of H2SO4 and a plating current density of about 10 mA/cm2 (slightly lower than the CCD of 15 mA/cm2). In agreement with theory, however, there were large voids at the Cu/Ru interface. - Simply increasing plating current density to allow plating of a void-free, continuous film onto a ruthenium interlayer also has disadvantages; generally, a high plating current density tends to result in poor gap fill. Plating current densities of less than about 10 mA/cm2 have been found to encourage bottom-up deposition of trenches and vias, such as
apertures 120, with agap fill layer 112, shown inFIGS. 1A-1C . In order to reduce the plating current density to the range suitable for bottom-up gap fill, the ion concentration of the plating bath may be increased. For example, it has been shown that a continuous 1000 Å copper film may be deposited on a 100 Å Ru film on a substrate using a plating bath with a H2SO4 concentration of 160 g/l and a plating current of 5 mA/cm2. Referring toFIG. 3 , 5 mA/cm2 is equal to the CCD for this particular acidic concentration. However, cross-section SEM pictures show that voids were formed at the Cu/Ru interface. When the plating current was raised to 10 mA/cm2 (2 times CCD of 5 mA/cm2) and the same plating bath was used, a continuous 5000 Å copper film was formed on a 100 Å Ru layer with no voids at the copper/Ru interface. - One of the reasons for the CCD dependence on bath acidity is related to the local electrochemical over-potential discussed above. In addition, higher acidity plating solutions may remove unwanted deposits from the surface and increase the activity of the plating surface. Increasing acid concentration to lower the CCD introduces other problems, however. Because the intention of direct plating is to form a uniform, conformal metal layer on a barrier layer, electrical conductivity of the bath should be reduced as much as is practicable. A more conductive plating bath, such as a bath containing a high concentration of acid, degrades the uniformity of the resultant film.
- Recent research presented by Chyan, et al. from University of North Texas in American Chemical Society National Meeting in New Orleans, La., held in Mar. 23 to Mar. 27, 2003, shows that ruthenium oxide (RuO2) has a metal-like conductivity, and copper also plates and adheres strongly to ruthenium oxide. The high CCD's observed on a ruthenium surface could be the result of unwanted deposits on the ruthenium surface. “Unwanted deposits”, as used herein, is defined to include unwanted oxidation of a deposited surface as well as organic contaminants that accumulate on the fresh metallic surface after deposition. A “pure” ruthenium surface is believed to be more active for Cu nucleation. Hence, removing the unwanted deposits by a pre-treatment process before copper plating may greatly reduce the plating current and the plating bath acidity required to form a continuous copper layer and avoid voids at the Cu/Ru interface. Embodiments of the invention contemplate a pre-treatment process that includes a cathodic pre-treatment of the barrier or barrier/adhesion layer, such as
barrier layer 106 or groupVIII metal interlayer 108, as shown inFIGS. 1A-1C . - The cathodic treatment mentioned above is an electrochemical treatment of a substrate surface in a copper-ion-free acid solution. An oxidized metallic surface, particularly a RuOx surface that has formed on a freshly deposited ruthenium barrier/adhesion layer on a substrate, may be cathodically reduced. Additionally, weakly-bound organic surface contaminants may be expelled from the surface by the cathodic polarization. The removal of these unwanted deposits on the substrate surface prior to electrochemical plating has been demonstrated to reduce the CCD of the barrier/adhesion layer. One possible reduction reaction is shown in equation (1):
RuO2+4H*+4 e−→Ru+2H2O (1) - The cathodic treatment may be performed in an electrochemical plating cell similar to the copper plating cell described below in association with
FIG. 5 , or in a treatment cell separated from the copper plating system. The cathodic treatment cell requires an anode, a cathode and a copper-ion-free acid bath. The acidic concentration range should be in the range between about 10 g/l to about 100 g/l, and preferably in the range between about 10 g/l to about 50 g/l. A preferred acid is H2SO4, but other types of acidic solutions, such as organic sulfonic acid solutions (e.g. methylsulfonic acid), may also be used. The acidic bath needs to be free of copper ions to prevent copper deposition on the surface during the cathodic treatment. Such deposition would be in the form of poorly nucleated copper islands, leading to poor adhesion and/or voids. - The cathodic treatment can be realized through potential control or current control. With the potential control approach, a reference electrode is needed to monitor the wafer potential, in addition to the working electrodes, which are the thin as-deposited Ru film on the wafer surface, and an anode. Potential control can be realized through a potentiostat. The controlled ruthenium electrode potential, with respect to the reference electrode, is in the range of about 0 volt to about −0.5 volt. In addition to RuOx reduction to ruthenium, H2 evolution may occur on the Ru film surface, hence, it is important to avoid applying a reduction potential to the substrate that is too high. With the current control approach, a cathodic current will be passed between the substrate, coated with a ruthenium film for example, and an anode. The current density should be in the range of about 0.05 mA/cm2 to about 1 mA/cm2. The treatment time should be in the range of about 2 seconds to about 30 minutes. However, in the interest of maintaining adequate throughput during large-scale processing of substrates, the treatment is preferably kept below 5 minutes.
- Another benefit of cathodically pre-treating a barrier or barrier/adhesion layer on a substrate, particularly when the layer is a group
VIII metal interlayer 108, is the improved adhesion between copper and the adhesion layer. Experimental results have shown that the adhesion is better between copper and a pre-treated, clean, and possibly oxide-free ruthenium surface due to a high-integrity Cu/Ru interface free of voids. Good interface integrity between the Cu and the Ru layers can be an important aspect in forming a reliable semiconductor device. Hence, having a pre-treated ruthenium surface is critical to achieve high quality copper deposition on ruthenium films. Additionally, cathodically pre-treating a ruthenium surface prior to copper plating may improve the substrate surface's hydrophilicity. The step coverage of copper plating on substrate features, such asapertures 120, may be improved, since the treated surface is more hydrophilic and, hence, more able to draw the plating solution deep into the features. - The experimental results and discussion related to Ru are merely used as examples. The inventive concept may also be applied to other group VIII metals, such as rhodium (Rh), osmium (Os) and iridium (Ir) and barrier materials, such as cobalt, titanium, titanium nitride, titanium silicon nitride, tantalum, tantalum nitride, tantalum silicon nitride, tungsten, tungsten nitride, a Ti—W alloy, and a ruthenium-tantalum alloy.
- Direct Plating on a Barrier Layer with a Complex Alkaline Electrolyte
- Embodiments of the invention teach the use of complexed copper sources contained within an alkaline plating solution for the direct plating of copper layers on barrier and/or barrier/adhesion layers. “Direct plating”, as used herein, is defined as the method of electrochemically plating a more conductive metal layer, such as
seed layer 111 inFIG. 2 , onto a substantially less conductive layer, such asconductive substrate surface 114, to facilitate the subsequent uniform, void-free deposition of agapfill layer 112 and/or anoverfill layer 113. This process may be performed in a plating cell similar to the electrochemical processing cell described below in conjunction withFIG. 5 . - A plating solution containing complexed copper sources has a significantly more negative deposition potential than does a plating solution containing free copper ions. Generally, complexed copper ions have a deposition potential from about −1.1 V to about −0.5 V, depending on the particular complexing agent. Free copper ions have deposition potentials in the range from about −0.3 V to about −0.1 V, when referenced to Ag/AgCl (1 M KCl), which has a potential of 0.235 V verses a standard hydrogen electrode. For example:
Cu2(C6H4O7)+2H2O→2Cu0+C6H8O7+O2 Δε=−0.7 V
Cu+2+2e −→Cu0 Δε=−0.2 V.
Further, the current dependence on potential for the complex bath is substantially reduced when compared to a bath with free copper ions. Therefore, the local current density variation across the substrate surface will be improved, even in the presence of a large potential gradient across the substrate surface due to the low electrical conductivity of thin barrier metals. This leads to better deposition uniformity across the substrate surface. A more detailed description of electrochemical polarization of copper complex baths may be found in commonly U.S. patent application Ser. No. 10/616,097 [APPM 8241], filed Jul. 8, 2003, which is hereby incorporated by reference in its entirety to the extent not inconsistent with the claimed invention. - Suitable plating solutions that may be used with the processes described herein to plate copper may include at least one copper source compound, at least one chelating or complexing compound, optional wetting agents or suppressors, optional pH adjusting agents and a solvent.
- Plating solutions contain at least one copper source compound complexed or chelated with at least one of a variety of ligands. Complexed copper includes a copper atom in the nucleus and surrounded by ligands, functional groups, molecules or ions with a strong affinity to the copper, as opposed to free copper ions with very low affinity, if any, to a ligand (e.g., water). Complexed copper sources are either chelated before being added to the plating solution or are formed in situ by combining a free copper ion source with a complexing agent. The copper atom may be in any oxidation state, such as 0, 1 or 2, before, during or after complexing with a ligand. Therefore, throughout the disclosure, the use of the word copper or elemental symbol Cu includes the use of copper metal (Cu0), cupric (Cu+1) or cuprous (Cu+2), unless otherwise distinguished or noted.
- Examples of suitable copper source compounds include copper citrate, copper ED, copper EDTA, among others. A particular copper source compound may have ligated varieties. For example, copper citrate may include at least one cupric atom, cuprous atom or combinations thereof and at least one citrate ligand and include Cu(C6H7O7), Cu2(C6H4O7), Cu3(C6H5O7) or Cu(C6H7O7)2. In another example, copper EDTA may include at least one cupric atom, cuprous atom or combinations thereof and at least one EDTA ligand and include Cu(C10H15O8N2), Cu2(C10H14O8N2), Cu3(C10H13O8N2), Cu4(C10H12O8N2) or Cu2(C10H12O8N2). Examples of suitable copper source compounds include copper sulfate, copper pyrophosphate and copper fluoroborate.
- The plating solution contains one or more chelating or complexing compounds that include compounds having one or more functional groups selected from the group of carboxylate groups, hydroxyl groups, alkoxyl, oxo acids groups, mixture of hydroxyl and carboxylate groups and combinations thereof. Further examples of suitable chelating compounds include compounds having one or more amine and amide functional groups, such as ethylenediamine (ED), diethylenetriamine, diethylenetriamine derivatives, hexadiamine, amino acids, ethylenediaminetetraacetic acid (EDTA), methylformamide or combinations thereof. The plating solution may include one or more chelating agents at a concentration in the range from about 0.02 M to about 1.6 M.
- The one or more chelating compounds may also include salts of the chelating compounds described herein, such as lithium, sodium, potassium, cesium, calcium, magnesium, ammonium and combinations thereof. The salts of chelating compounds may completely or only partially contain the aforementioned cations (e.g., sodium) as well as acidic protons, such as Nax(C6H8-xO7) or NaxEDTA, whereas X=1-4. Such salt combines with a copper source to produce NaCu(C6H5O7). Examples of suitable inorganic or organic acid salts include ammonium and potassium salts or organic acids, such as ammonium oxalate, ammonium citrate, ammonium succinate, monobasic potassium citrate, dibasic potassium citrate, tribasic potassium citrate, potassium tartrate, ammonium tartrate, potassium succinate, potassium oxalate, and combinations thereof. The one or more chelating compounds may also include complexed salts, such as hydrates (e.g., sodium citrate dihydrate).
- Wetting agents or suppressors may be added to the solution in a range from about 10 ppm to about 2,000 ppm, preferably in a range from about 50 ppm to about 1,000 ppm. Suppressors include polyacrylamide, polyacrylic acid polymers, polycarboxylate copolymers, polyethers or polyesters of ethylene oxide and/or propylene oxide (EO/PO), coconut diethanolamide, oleic diethanolamide, ethanolamide derivatives or combinations thereof.
- One or more pH-adjusting agents are optionally added to the plating solution to achieve a pH≧7.0, preferably between about 7.0 and about 9.5. The amount of pH adjusting agent can vary as the concentration of the other components is varied in different formulations. Different compounds may provide different pH levels for a given concentration, for example, the composition may include between about 0.1% and about 10% by volume of a base, such as potassium hydroxide, ammonium hydroxide or combinations thereof, to provide the desired pH level. The one or more pH adjusting agents may also include acids, including carboxylic acids, such as acetic acid, citric acid, oxalic acid, phosphate-containing components including phosphoric acid, ammonium phosphates, potassium phosphates, inorganic acids, such as sulfuric acid, nitric acid, hydrochloric acid and combinations thereof.
- In an exemplary direct plating process using a Cu-ED alkaline electrolyte, a constant cathodic current is applied to the substrate resulting in a constant current density which may be in a range between about 1 mA/cm2 to about 10 mA/cm2 for a time period between about 0.1 seconds and 5.0 seconds. This results in the formation of a copper seed layer between about 50 Å and about 300 Å thick on the barrier layer.
- Alternately, in order to ensure that a uniform, void-free seed layer is formed on a substrate during the above-described direct plating process, a “nucleation spike” or “nucleation pulse” may be used when the substrate surface is first brought in contact with the plating solution. “Nucleation spike” or “nucleation pulse,” as used herein, is defined as an initial higher plating current level intended to help the nucleation of the copper deposition on the substrate surface, wherein the initial plating current is at least equal to, or ideally greater than, the CCD. This plating current may exceed the maximum plating current that typically allows for bottom-up gapfill of substrate features and therefore is only applied for a short time. For example, in the case of plating a copper seed layer onto a ruthenium barrier layer, a constant plating current in the range of about 5 mA/cm2 to about 20 mA/cm2 is applied to the barrier layer during the nucleation pulse for about 0.1 to about 5 seconds. This allows the formation of a conformal, uniform and void-free layer on the substrate, such as
seed layer 111, as shown inFIG. 2 . - Plating on Copper Seed with a Complex Alkaline Electrolyte
- Aspects of the invention teach the use of a complex alkaline electrolyte for plating a gapfill layer, such as gapfill layer 112 (see
FIG. 2 ), onto a seed layer, such asseed layer 111, that has been directly deposited on a barrier layer via an alkaline solution ECP process. This process may be performed in an electrochemical plating cell similar to the electrochemical processing cell described below in conjunction withFIG. 5 . - This process is similar to that described above for direct plating on a barrier layer with a complex alkaline electrolyte. Process parameters are believed to enhance the bottom-up gapfill process, however, including plating current and deposition time. Generally, higher deposition rates and, hence, plating current densities, may be utilized for this process.
- The bath used for this process is also similar to that used for direct plating. The complex alkaline bath for gapfill contains at least one copper source compound and at least one complexing compounds, as detailed previously. The one or more complexing compounds may also include salts of the chelating compounds, listed above. The bath also may contain wetting agents and one or more pH-adjusting agents (see above). Concentrations of the bath's components are believed to enhance the bottom-up gapfill process.
- Additionally, the use of a nucleation pulse is unnecessary for the formation of a uniform, void-free metal layer to be formed on the seed layer.
- Plating on Copper Seed with an Acidic Electrolyte
- Aspects of the invention teach the use of a conventional acid electrolyte for plating a gap fill layer onto a seed layer that has been directly deposited on a barrier layer via an alkaline solution ECP process. ECP gapfill deposition of copper onto a copper seed layer using an acidic plating solution is well known in the art and may be performed in an electrochemical plating cell similar to the copper plating cell described below in conjunction with
FIGS. 4 and 5 . This process may also be used for depositing a copper overfill layer on a substrate, such asoverfill layer 113, inFIG. 2 . - A conventional, i.e., non-complex, electrochemical plating solution for ECP generally includes a copper source, an acid source, a chlorine ion source, and at least one plating solution additive, i.e., levelers, suppressors, accelerators, antifoaming agents, etc. For example, the plating solution may contain between about 30 g/l and about 60 g/l of copper, between about 10 g/l to about 50 g/l of sulfuric acid, between about 20 and about 100 ppm of chlorine ions, between about 5 and about 30 ppm of an additive accelerator, between about 100 and about 1000 ppm of an additive suppressor, and between about 1 and about 6 ml/l of an additive leveler. The plating current may be in the range from about 2 mA/cm2 to about 10 mA/cm2 for filling about 300 Å to about 3000 Å copper into the submicron trench and/or via structure. A substantially similar process is used for an overfill plating process, in which an additional 5000 Å to 10,000 Å of copper is plated on to a substrate to complete a copper interconnect layer. Examples of copper plating chemistries and processes can be found in commonly assigned U.S. patent application Ser. No. 10/616,097, titled “Multiple-Step Electrodeposition Process For Direct Copper Plating On Barrier Metals”, filed on Jul. 8, 2003, and U.S. patent application NO. 60/510,190, titled “Methods And Chemistry For Providing Initial Conformal Electrochemical Deposition Of Copper In Sub-Micron Features”, filed on Oct. 10, 2003.
- Exemplary Plating Apparatus
- Electrochemical Processing System
-
FIG. 4 is a top plan view of an embodiment of an electrochemical processing system (ECPS) 400 capable of implementing the methodology of the present invention. TheECPS 400 generally includes aprocessing base 413 having arobot 420 centrally positioned thereon. Therobot 420 generally includes one ormore robot arms robot 420 and therobot arms robot 420 may insert and remove substrates to and from a plurality ofprocessing locations base 413. Processing locations may be configured as electroless plating cells, electrochemical processing cells, substrate rinsing and/or drying cells, substrate bevel clean cells, substrate surface clean or preclean cells and/or other processing cells that are advantageous to plating processes. Preferably, embodiments of the present invention are conducted within at least one of theprocessing locations - The
ECPS 400 further includes a factory interface, orFI 430. TheFI 430 generally includes at least oneFI robot 432 positioned adjacent one side of theFI 430 that is adjacent to theprocessing base 413. TheFI robot 432 is positioned to access asubstrate 426 fromsubstrate cassettes 434. TheFI robot 432 delivers thesubstrate 426 to one ofprocessing locations FI robot 432 may be used to retrieve substrates from one of theprocessing locations situation FI robot 432 may deliver thesubstrate 426 back to one of thecassettes 434 for removal from thesystem 400. Further,robot 432 also extends into alink tunnel 415 that connectsfactory interface 430 to processing mainframe orplatform 413. Additionally,FI robot 432 is configured to access ananneal chamber 435 positioned in communication with theFI 430. - Electrochemical Plating Cell
-
FIG. 5 illustrates a partial perspective and sectional view of an exemplary electrochemical processing cell, hereinafter referred to as platingcell 500, that may be implemented inprocessing locations FIG. 4 . The platingcell 500 generally includes aplating head assembly 600, aframe member 503, anouter basin 501 and aninner basin 502 positioned withinouter basin 501. - The plating
head assembly 600 includes a receiving member 601for supporting and rotating a substrate during immersion into the electrochemical processing solution and during electrochemical processing. In this example, receivingmember 601 includes acontact ring 602 and athrust plate assembly 604 that are separated by aloading space 606. Thecontact ring 602 may be adapted to make electrical contact around the periphery of the substrate so that the necessary electrical bias may be applied to the substrate. Thecontact ring 602 may be further adapted to include a reference electrode that is located close to the substrate surface. A more detailed description of thecontact ring 602 and thrustplate assembly 604 may be found in commonly assigned U.S. patent application Ser. No. 10/278,527, filed on Oct. 22, 2002 and entitled “Plating Uniformity Control By Contact Ring Shaping”, and commonly assigned U.S. Pat. No. 6,251,236 entitled Cathode Contact Ring for Electrochemical Deposition, both of which are hereby incorporated by reference in their entirety to the extent not inconsistent with the present invention. - The
frame member 503 of platingcell 500 supports anannular base member 504 on an upper portion thereof. Sinceframe member 503 is elevated on one side, the upper surface ofbase member 504 is generally tilted from the horizontal at an angle that corresponds to the tilt angle offrame member 503 relative to a horizontal position.Base member 504 includes a disk-shapedanode 505. Platingcell 500 may be positioned at a tilt angle, i.e., theframe portion 503 of platingcell 500 may be elevated on one side such that the components of platingcell 500 are tilted between about 3° and about 30°. -
Inner basin 502 is generally configured to contain a processing solution, such as a plating solution or a cathodic pre-treatment solution, during electrochemical processing of substrates. During processing, the processing solution is generally continuously supplied toinner basin 502, and therefore, the processing solution continually overflows theuppermost point 502 a, generally termed a “weir”, ofinner basin 502 and is collected byouter basin 501 and drained therefrom for chemical management and recirculation. The exemplary electrochemical processing cell is further illustrated in commonly assigned U.S. patent application Ser. No. 10/268,284, filed on Oct. 9, 2002, and entitled “Electrochemical Processing Cell”, claiming priority to U.S. Provisional Application Ser. No. 60/398,345, which was filed on Jul. 24, 2002, both of which are incorporated herein by reference in their entireties. - In an exemplary electrochemical process, such as
substrate process sequence 610, described below in conjunction withFIG. 6 , a substrate may be transferred into an electrochemical processing cell, such as platingcell 500 for example, and positioned face-down oncontact ring 602.Thrust plate assembly 604 holds the substrate in place during processing. The substrate is then immersed in the electrolyte solution fillinginner basin 502, typically while being rotated by thecontact ring 602 between about 5 rpm and about 60 rpm. The electrolyte solution may comprise an acidic, copper free solution, a complexed-copper alkaline solution, or a conventional acidic copper-containing solution, depending on the process being performed on the substrate. The substrate may be rotated between about 10 rpm and about 100 rpm during processing step bycontact ring 602. The time required for processing is dependent on each particular process, such as cathodic pre-treatment, seed layer deposition, seed layer and gapfill layer deposition, etc. Once the processing step is complete, the bias is then removed and the substrate is positioned above the electrolyte solution anduppermost point 502 a ofinner basin 502 for removal from platingcell 500. Prior to removal from platingcell 500, the substrate may be rotated between about 100 and 1000 rpm for between about 1 second and about 10 seconds in order to remove excess solution from the substrate. -
FIG. 6 is a flow chart of asubstrate process sequence 610. Embodiments include a method for depositing a metal layer onto a barrier and/or adhesion layer on a substrate that includes: - A
cathodic pre-treatment 611 of the barrier or adhesion layer in an acid-containing bath. -
Seed layer deposition 612 of a continuous, void-free seed layer onto the cathodically pre-treated layer. -
Gapfill layer deposition 613 of a gapfill layer on the seed layer. -
Optional overfill deposition 614 of an ECP overfill layer. - In one embodiment, a
cathodic pre-treatment 611 of a substrate surface, such asconductive substrate surface 114 inFIG. 2 , is performed. As noted above, thecathodic pre-treatment 611 may reduce the critical current density required to form a uniform, void-free, conformal metal layer on a barrier layer. - Next,
seed layer deposition 612 takes place on the substrate, wherein a seed layer, such asseed layer 111 inFIG. 2 , is directly plated ontoconductive substrate surface 114 using an electrochemical process with a complex alkaline bath. In one aspect, a nucleation pulse is used to improve the quality of the seed layer. In one aspect, thecathodic pre-treatment 611 andseed layer deposition 612 are performed on the same electrochemical processing system, such asECPS 400, described above in conjunction withFIG. 4 , reducing the exposure time of the cathodically treated surface to oxygen and ambient contamination to minutes or even seconds. This minimizes the formation of unwanted deposits on the treated barrier layer surface prior to seed layer deposition. -
Gapfill layer deposition 613 then takes place on the substrate, wherein a gapfill layer, such asgapfill layer 112 inFIG. 2 , is plated ontoseed layer 111 using the electrochemical gapfill process with a complex alkaline bath described above. In one aspect, theseed layer deposition 612 and thegapfill layer deposition 613 are performed sequentially in the same plating cell using the same plating solution. This is especially useful for gapfill of interconnect features smaller than 65 nm; such small interconnect features are particularly sensitive to the formation of voids during gapfill as well as the presence of unwanted deposits at the interface between the seed layer and the gapfill layer. Because a single bath is used for both process steps, the surface of the seed layer is never exposed to atmosphere prior togapfill layer deposition 613, eliminating the possibility of unwanted oxidation. Further, there is virtually no time for organic contaminants to accumulate on the seed layer surface since theseed layer deposition 612 may be followed immediately by thegapfill layer deposition 613. - An
overfill deposition 614 then may be performed on the substrate, wherein an ECP overfill layer, such asoverfill layer 113, may be deposited to complete formation of an interconnect layer. In one aspect, theoverfill deposition 614 is performed sequentially in the same plating cell asgapfill deposition 613, using the same plating solution. This avoids oxidation and organic contamination of the gapfill layer prior to overfilldeposition 614. In another aspect, theoverfill deposition 614 is performed via a conventional acidic electrolyte ECP process. In this aspect, an additional rinsing step is performed on the substrate between thegapfill layer deposition 613 and theoverfill deposition 614 to prevent cross-contamination of the plating solution used for ECP overfill. The additional rinsing step may be performed in a dedicated rinsing chamber, preferably located on the same electrochemical processing system wherein thesubstrate process sequence 610 may be performed. The substrate is rinsed with an aqueous solution while rotating at a rate from about 20 to about 400 rpm and subsequently dried via gas flow and/or spin-drying. Due to the inherent incompatibility of acidic and basic solutions, as well as the serious problems associated with cross-contamination of organic additives between plating solutions, rigorous cleaning of the plating cell would have to be performed between thegapfill layer deposition 613 and theoverfill deposition 614 for each substrate processed therein. Instead, it is preferred that two separate ECP cells are used to complete the formation ofcopper layer 110 inapertures 120 on a substrate: one cell dedicated to an alkaline-based plating process, i.e., theseed layer deposition 612 and thegapfill layer deposition 613, and one cell dedicated to acid-based plating processes, i.e., theoverfill deposition 614. To minimize waiting time and the associated oxidation and contamination of the gapfill layer prior to theoverfill deposition 614, both ECP cells are preferably situated on the same substrate processing platform, such as the exemplary plating system described below in conjunction withFIG. 4 . Theoverfill deposition 614 is particularly beneficial when there is a need to fill large and small interconnect features on a substrate surface at the same time; the small or high aspect ratio interconnect features are filled during thegapfill layer deposition 613 and the larger, low aspect ratio features are filled with the higher deposition rate ECP overfill process. - In another embodiment, a
cathodic pre-treatment 611 is performed on a substrate surface, such asconductive substrate surface 114 inFIG. 2 . As stated above in the previous embodiment, thecathodic pre-treatment 611 reduces the critical current density. - Next, the
seed layer deposition 612 takes place on the substrate, wherein a seed layer is directly plated ontoconductive substrate surface 114 using an electrochemical process with a complex alkaline bath. In one aspect, a nucleation pulse is used to improve the quality of the seed layer. In one aspect, thecathodic pre-treatment 611 and theseed layer deposition 612 are performed on the same electrochemical processing system. In another aspect, the smallest interconnect features on a substrate are completely filled during theseed layer deposition 612, whereas only a conformal seed layer is formed on the surfaces of larger interconnect features. As described above in theseed layer deposition 612 of the previous embodiment, it is beneficial for thecathodic pre-treatment 611 and theseed layer deposition 612 to be performed on the same electrochemical processing system to minimize the formation of unwanted deposits on the treated barrier layer surface prior to seed layer deposition. - In
gapfill layer deposition 613, a gapfill layer is plated ontoseed layer 111 using an electrochemical gapfill process with a conventional acid bath as described above. No complexing agents are necessary in this plating process. Preferably,gapfill layer deposition 613 is performed in a different electrochemical processing cell than theseed layer deposition 612 to isolate acid-based and alkaline-based processes. In one aspect, an additional rinsing step is performed on the substrate between theseed layer deposition 612 and thegapfill deposition 613 to prevent cross-contamination of the plating solution used for gapfill. The additional rinsing step is substantially similar to that described above inoverfill deposition 614 of the previous embodiment. - In
overfill deposition 614 an ECP overfill layer may be deposited to complete formation of an interconnect layer. In one aspect, overfilldeposition 614 is performed via a conventional acidic electrolyte ECP process.Overfill deposition 614 may be performed in the same electrochemical processing cell asgapfill layer deposition 613 to prevent oxidation and other surface contaminants form forming at the interface between the gapfill layer and the overfill layer. In another aspect, overfilldeposition 614 is performed on the same electrochemical processing system asgapfill layer deposition 613, but in a different electrochemical processing cell. - This embodiment allows for gapfill of the smallest features on a substrate during
cathodic pre-treatment 611, wherein the seed layer is deposited for larger interconnect features. Subsequently, gapfill of the larger features as well as overfill deposition of the interconnect layer may be performed on a substrate in a single ECP cell. This method increases the productivity of electrochemical processing systems by combining two process steps into a single plating cell. - Although several preferred embodiments which incorporate the teachings of the present invention have been shown and described in detail, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings.
- While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims (23)
1. A method for depositing copper onto a substrate surface, wherein the substrate surface comprises an interlayer, comprising:
depositing an interlayer on a substrate surface;
pre-treating the substrate surface to remove unwanted deposits from the surface of the interlayer by a cathodic treatment in an acid-containing bath to reduce a critical current density during plating; and
depositing a first copper layer onto the interlayer, wherein the first copper layer is a continuous copper layer and wherein the process of depositing the first copper layer onto the interlayer comprises:
placing the substrate surface into contact with a copper solution, wherein the copper solution comprises complexed copper ions, a complexing agent and a pH equal to or greater than 7.0; and
applying a first plating bias to the substrate surface.
2. The method of claim 1 , wherein the interlayer is selected from the group consisting of cobalt, titanium, titanium nitride, titanium silicon nitride, tantalum, tantalum nitride, tantalum silicon nitride, tungsten, tungsten nitride, a Ti—W alloy, ruthenium, a ruthenium-tantalum alloy, rhodium, osmium or iridium.
3. The method of claim 1 , wherein the complexed copper ions are selected from the group consisting of copper ED, copper EDTA, copper citrate and combinations thereof.
4. The method of claim 1 , wherein the acid-containing bath is positioned on the same copper plating system as the copper solution.
5. The method of claim 1 , wherein the cathodic treatment is performed at a potential in the range of about 0 volt to about −1.0 volt.
6. The method of claim 1 , wherein the cathodic treatment is performed at a current density in the range of about 0.05 mA/cm2 to about 5 mA/cm2.
7. The method of claim 1 , wherein the acid-containing bath contains sulfuric acid, wherein the concentration of the sulfuric acid is in the range between about 10 g/l to about 50 g/l.
8. The method of claim 1 , wherein the process of applying a first plating bias comprises plating copper onto the interlayer with a plating current that is at least equal to a critical current density.
9. The method of claim 8 , wherein the critical current density is less than 10 mA/cm2.
10. The method of claim 1 , further comprising depositing a second copper layer onto the first copper layer, wherein the process of depositing the second copper layer comprises:
placing the substrate surface into a second copper solution, wherein the second copper solution is acidic and includes free-copper ions; and
applying a second plating bias to the substrate surface.
11. The method of claim 10 , further comprising:
applying a third plating bias to the substrate surface while in contact with the second copper solution to deposit a third copper layer onto the second copper layer.
12. The method of claim 1 , further comprising:
applying a second plating bias to the substrate surface while in contact with the copper solution to deposit a second copper layer onto the first copper layer.
13. The method of claim 1 , further comprising:
applying a nucleation bias to the substrate surface after placing the substrate surface into the copper solution and prior to applying a first plating bias to the substrate surface, the nucleation bias being configured to generate a first current density across the substrate surface greater than a critical current density.
14. The method of claim 2 , wherein the interlayer is an interlayer on which a discontinuous copper film has been deposited.
15. A method for depositing copper onto a substrate surface, wherein the substrate surface comprises an interlayer, comprising:
depositing an interlayer on a substrate surface;
pre-treating the substrate surface to remove unwanted deposits from the surface of the interlayer by a cathodic treatment in an acid-containing bath to reduce a critical current density during plating;
depositing a first copper layer onto the interlayer, wherein the first copper layer is a continuous copper layer and wherein the process of depositing the first copper layer onto the interlayer comprises:
placing the substrate surface into contact with a copper solution, wherein the copper solution comprises complexed copper ions, a complexing agent and a pH equal to or greater than 7; and
applying a first plating bias to the substrate surface; and
applying a second plating bias to the substrate surface while in contact with the copper solution to deposit a second copper layer onto the first copper layer.
16. The method of claim 15 , wherein the interlayer is selected from the group consisting of cobalt, titanium, titanium nitride, titanium silicon nitride, tantalum, tantalum nitride, tantalum silicon nitride, tungsten, tungsten nitride, a Ti—W alloy, ruthenium, a ruthenium-tantalum alloy, rhodium, osmium and iridium.
17. The method of claim 15 , wherein the complexed copper ions are selected from the group consisting of copper ED, copper EDTA, copper citrate and combinations thereof.
18. The method of claim 15 , further comprising:
applying a third plating bias to the substrate surface while in contact with the copper solution to deposit a third copper layer onto the second copper layer.
19. A method for depositing copper onto a substrate surface, wherein the substrate surface comprises a ruthenium-tantalum alloy, comprising:
depositing a ruthenium-tantalum alloy on a substrate surface; and
depositing a first copper layer onto the ruthenium-tantalum alloy, wherein the first copper layer is a continuous copper layer and wherein the process of depositing the first copper layer onto the ruthenium-tantalum alloy comprises:
placing the substrate surface into contact with a copper solution, wherein the copper solution comprises complexed copper ions, a complexing agent and a pH equal to or greater than 7.0; and
applying a first plating bias to the substrate surface.
20. The method of claim 19 , wherein the ruthenium-tantalum alloy contains between about 70 atomic % and about 95 atomic % of ruthenium and the balance tantalum.
21. The method of claim 20 , wherein the thickness of the ruthenium-tantalum alloy is between about 5 Å to about 200 Å.
22. The method of claim 19 , wherein the complexed copper ions are selected from the group consisting of copper ED, copper EDTA, copper citrate and combinations thereof.
23. The method of claim 19 , further comprising depositing a second copper layer onto the first copper layer wherein the process of depositing the second copper layer comprises:
applying a second plating bias to the substrate surface while in contact with the copper solution to deposit a second copper layer onto the first copper layer.
Priority Applications (5)
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US11/255,368 US20070125657A1 (en) | 2003-07-08 | 2005-10-21 | Method of direct plating of copper on a substrate structure |
US11/373,635 US20060283716A1 (en) | 2003-07-08 | 2006-03-09 | Method of direct plating of copper on a ruthenium alloy |
PCT/US2006/060072 WO2007111676A2 (en) | 2005-10-21 | 2006-10-19 | Method of direct plating of copper on a substrate structure |
TW095138839A TWI376433B (en) | 2005-10-21 | 2006-10-20 | Method of direct plating of copper on a substrate structure |
US13/150,850 US20110259750A1 (en) | 2003-07-08 | 2011-06-01 | Method of direct plating of copper on a ruthenium alloy |
Applications Claiming Priority (7)
Application Number | Priority Date | Filing Date | Title |
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US10/616,097 US20050006245A1 (en) | 2003-07-08 | 2003-07-08 | Multiple-step electrodeposition process for direct copper plating on barrier metals |
US57912904P | 2004-06-10 | 2004-06-10 | |
US62117304P | 2004-10-21 | 2004-10-21 | |
US62121504P | 2004-10-21 | 2004-10-21 | |
US11/007,857 US20050274621A1 (en) | 2004-06-10 | 2004-12-09 | Method of barrier layer surface treatment to enable direct copper plating on barrier metal |
US11/012,965 US20050274622A1 (en) | 2004-06-10 | 2004-12-15 | Plating chemistry and method of single-step electroplating of copper on a barrier metal |
US11/255,368 US20070125657A1 (en) | 2003-07-08 | 2005-10-21 | Method of direct plating of copper on a substrate structure |
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US11/007,857 Continuation-In-Part US20050274621A1 (en) | 2003-07-08 | 2004-12-09 | Method of barrier layer surface treatment to enable direct copper plating on barrier metal |
US11/012,965 Continuation-In-Part US20050274622A1 (en) | 2003-07-08 | 2004-12-15 | Plating chemistry and method of single-step electroplating of copper on a barrier metal |
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