US3098043A - Etchant for molybdenum - Google Patents
Etchant for molybdenum Download PDFInfo
- Publication number
- US3098043A US3098043A US132018A US13201861A US3098043A US 3098043 A US3098043 A US 3098043A US 132018 A US132018 A US 132018A US 13201861 A US13201861 A US 13201861A US 3098043 A US3098043 A US 3098043A
- Authority
- US
- United States
- Prior art keywords
- per liter
- etching
- etchant
- molybdenum
- oxalate
- 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.)
- Expired - Lifetime
Links
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 title claims description 12
- 229910052750 molybdenum Inorganic materials 0.000 title claims description 11
- 239000011733 molybdenum Substances 0.000 title claims description 11
- 238000005530 etching Methods 0.000 claims description 18
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 5
- 229910052783 alkali metal Inorganic materials 0.000 claims description 4
- 239000007864 aqueous solution Substances 0.000 claims description 4
- 150000001340 alkali metals Chemical class 0.000 claims description 3
- YAGKRVSRTSUGEY-UHFFFAOYSA-N ferricyanide Chemical compound [Fe+3].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-] YAGKRVSRTSUGEY-UHFFFAOYSA-N 0.000 claims description 2
- XLYOFNOQVPJJNP-PWCQTSIFSA-N Tritiated water Chemical compound [3H]O[3H] XLYOFNOQVPJJNP-PWCQTSIFSA-N 0.000 claims 1
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims 1
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 27
- 239000000243 solution Substances 0.000 description 15
- -1 potassium ferricyanide Chemical compound 0.000 description 12
- ZNCPFRVNHGOPAG-UHFFFAOYSA-L sodium oxalate Chemical compound [Na+].[Na+].[O-]C(=O)C([O-])=O ZNCPFRVNHGOPAG-UHFFFAOYSA-L 0.000 description 9
- 229940039790 sodium oxalate Drugs 0.000 description 9
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 6
- 239000000203 mixture Substances 0.000 description 5
- MUBZPKHOEPUJKR-UHFFFAOYSA-L Oxalate Chemical compound [O-]C(=O)C([O-])=O MUBZPKHOEPUJKR-UHFFFAOYSA-L 0.000 description 4
- 239000003513 alkali Substances 0.000 description 4
- 239000003223 protective agent Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 150000002500 ions Chemical class 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- IRXRGVFLQOSHOH-UHFFFAOYSA-L dipotassium;oxalate Chemical compound [K+].[K+].[O-]C(=O)C([O-])=O IRXRGVFLQOSHOH-UHFFFAOYSA-L 0.000 description 2
- 238000005187 foaming Methods 0.000 description 2
- 229940039748 oxalate Drugs 0.000 description 2
- PWVUXRBUUYZMKM-UHFFFAOYSA-N 2-(2-hydroxyethoxy)ethyl octadecanoate Chemical compound CCCCCCCCCCCCCCCCCC(=O)OCCOCCO PWVUXRBUUYZMKM-UHFFFAOYSA-N 0.000 description 1
- 208000027418 Wounds and injury Diseases 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000006735 deficit Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 239000004519 grease Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 208000014674 injury Diseases 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 150000001455 metallic ions Chemical class 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 150000003891 oxalate salts Chemical class 0.000 description 1
- 235000006408 oxalic acid Nutrition 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F1/00—Etching metallic material by chemical means
- C23F1/10—Etching compositions
- C23F1/14—Aqueous compositions
- C23F1/32—Alkaline compositions
- C23F1/38—Alkaline compositions for etching refractory metals
Definitions
- This invention relates to a composition or solution for the rapid etching of molybdenum.
- a standard formulation for etching thin molybdenum sheet consists of an aqueous solution of 360 grams per liter of potassium ferricyanide and 36 grams per liter of sodium hydroxide; this solution is ordinarily applied by spraying or splashing upon the material to be etched, the solution temperature being maintained in the vicinity of 200 degrees Fahrenheit. Neither the concentration of chemicals nor the temperature is at all critical; therefore, a solution of 0.3 mole per liter of potassium ferricyanide and 0.25 mole per liter of sodium hydroxide and a temperature of 120 degrees Fahrenheit are also quite satisfactory. However, in both instances the rate of etching is quite slow, from twenty to thirty minutes being required to etch away 2 mils of molybdenum.
- composition of matter or solution for effectively accelerating the etching of molybdenum.
- composition suitable for the practice of this invention is the following:
- the attack of the etchant upon the protective agent or resist is a concomitant which frequently occurs to an undesired degree.
- the addition of the etching accelerator does not noticeably increase the rate of attack of the etchant upon the protective agent or resist, and therefore the overall lowering of the etching time materially lessens the opportunity for the etchant to penetrate the protective agent or resist.
- the reduction in injury to the resist also permits the utilization of more violent mechanical agitation or splashing thereby resulting in more sharply defined etched boundaries in the finished product.
- Oxalate ion may be provided by the addition of oxalic acid and an equivalent amount of the alkali chosen, instead of the oxalate as such.
- An aqueous bath for etching molybdenum comprising water, .091 mole per liter of potassium ferricyanide, .075 mole per liter of sodium hydroxide and .00375 mole per liter of sodium oxalate;
- An aqueous bath for etching molybdenum comprising water, 1.5 moles per liter of potassium ferricyanide, 1.25 moles per liter of sodium hydroxide, and .045 mole per liter of sodium oxalate.
- An aqueous solution for etching molybdenum comprising water, potassium ferricyanide in the range of concentration .6 mole to .8 mole per liter, sodium hydroxide in the range of concentration .5 mole to .63 mole per liter, and sodium oxalate in the range of concentration .022 to .045 mole per liter.
- An aqueous solution for etching molybdenum comprising water, potassium ferricyanide in the range of concentration .6 to .8 mole per liter, potassium hydroxide in the range of concentration .5 to .63 mole per liter, and potassium oxalate in the range of concentration .022 to .045 mole per liter.
Description
CROSS REFERENCE United States Patent 3,098,043 ETCHANT FOR MOLYBDENUM Douglas C. Wendell, Jr., Malvern, Pa., assignor to Burroughs Corporation, Detroit, Mich., a corporation of Michigan No Drawing. Filed Aug. 17, 1961, Ser. No. 132,018 6 Claims. (Cl. 252-795) This invention is a continuation-in-part of an application entitled Etchant for Molybdenum, Serial No. 848,233, filed on October 23, 1959, and now abandoned.
This invention relates to a composition or solution for the rapid etching of molybdenum.
A standard formulation for etching thin molybdenum sheet consists of an aqueous solution of 360 grams per liter of potassium ferricyanide and 36 grams per liter of sodium hydroxide; this solution is ordinarily applied by spraying or splashing upon the material to be etched, the solution temperature being maintained in the vicinity of 200 degrees Fahrenheit. Neither the concentration of chemicals nor the temperature is at all critical; therefore, a solution of 0.3 mole per liter of potassium ferricyanide and 0.25 mole per liter of sodium hydroxide and a temperature of 120 degrees Fahrenheit are also quite satisfactory. However, in both instances the rate of etching is quite slow, from twenty to thirty minutes being required to etch away 2 mils of molybdenum.
Among the objects of the present invention is the provision of a composition of matter or solution for effectively accelerating the etching of molybdenum.
I have found that the addition of sodium oxalate to the etchant reduces the etching time very markedly. For example, a solution of optimum composition is the folowing:
Moles per liter of solution Potassium ferricyanide .6 to .8 Sodium hydroxide .5 to .63 Sodium oxalate .022 to .045
Moles per liter of solution Potassium ferricyanide 1.5
Sodium hydroxide 1.25 Sodium oxalate .03
was found to etch almost as rapidly.
Another composition suitable for the practice of this invention is the following:
Moles per liter of solution Potassium ferricyanide .6 to .8 Potassium hydroxide .5 to .63 Potassium oxalate .022 to .045
When light-sensitive resists or other types of protective agents are employed in connection with an etching process, the attack of the etchant upon the protective agent or resist is a concomitant which frequently occurs to an undesired degree. In the practice of my invention, the addition of the etching accelerator does not noticeably increase the rate of attack of the etchant upon the protective agent or resist, and therefore the overall lowering of the etching time materially lessens the opportunity for the etchant to penetrate the protective agent or resist. The reduction in injury to the resist also permits the utilization of more violent mechanical agitation or splashing thereby resulting in more sharply defined etched boundaries in the finished product.
It is the oxalate ion which produces the beneficial effects I have observed. This may be deduced from the Patented July 16, 1963 fact that the alkali ion added by the addition of sodium oxalate is negligible by comparison with the amount of alkali ion already present. It is thus clear that it is quite immaterial whether the metallic ions present be of any particular chemical family provided their nature is consistent with the solubility of all the negative ions contained by the described etchant, and with the alkalin i-ty normally occurring in etchant of the described com position. As a practical matter, the cheaper and more readily available alkali metals will, of course, be preferred, since the alkaline earths (one of which is a famed source of cheap alkali) are noted for the insolubility of their oxalates. Oxalate ion may be provided by the addition of oxalic acid and an equivalent amount of the alkali chosen, instead of the oxalate as such.
An increase in the temperature of the solution will increase the etching speed, but may produce problems of evaporation of the solvent. The extremely high alkalinity of the solution tends to foaming in a mechanically agitated etcher such as a splash etcher. I have found that from one-tenth to three-tenths of a milliliter of a foam reducer, such as diethylene glycol monostearate added to each liter of etchant, will reduce foaming without impairment of the etching action.
It is part of the known art that the surfaces to be etched must be free from contaminations such as grease which would tend to shield them from the etchant.
Reduced concentrations of the etchant chemicals will reduce the speed of etching so much that the improvement produced by the addition of oxalate ion according to my invention will only be mildly effective; consequently, the use of extremely dilute solutions is not desirable. On the other hand, too high a concentration impairs the uniformity of etching, and tends somewhat to cause undercutting beneath a protective resist. If
EXAMlNER these effects are not objectionable, such high eoncentra tions may be used.
In the light of these desiderata, the following has proven to be a practical solution of reduced concentration:
Moles per liter Potassium ferricyanide .091 Sodium hydroxide .075 Sodium oxalate .00375 Stated in ionic terms this solution supra would be expressed as follows:
Moles per liter Fe(CN) (ferricyanide ion) .091 (OH) (hydroxide ion) .075
(C O (oxalate ion) .00375 Similarly, in certain applications, the following has proven to be a practical solution of high concentration:
Moles per liter Potassium ferricyanide 1.5 Sodium hydroxide 1.25 Sodium oxalate .045
Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced other than as specifically described and illustrated.
and .00375 to .045 mole per liter of an alkali metal oxalate for use as an etching accelerator.
3. An aqueous bath for etching molybdenum comprising water, .091 mole per liter of potassium ferricyanide, .075 mole per liter of sodium hydroxide and .00375 mole per liter of sodium oxalate;
4. An aqueous bath for etching molybdenum comprising water, 1.5 moles per liter of potassium ferricyanide, 1.25 moles per liter of sodium hydroxide, and .045 mole per liter of sodium oxalate.
5. An aqueous solution for etching molybdenum comprising water, potassium ferricyanide in the range of concentration .6 mole to .8 mole per liter, sodium hydroxide in the range of concentration .5 mole to .63 mole per liter, and sodium oxalate in the range of concentration .022 to .045 mole per liter.
6. An aqueous solution for etching molybdenum comprising water, potassium ferricyanide in the range of concentration .6 to .8 mole per liter, potassium hydroxide in the range of concentration .5 to .63 mole per liter, and potassium oxalate in the range of concentration .022 to .045 mole per liter.
References Cited in the file of this patent UNITED STATES PATENTS
Claims (1)
1. AN AQUEOUS SOLUTION FOR ETCHING MOLYBDENUM COMPRISING WATER, 0.91 TO 1.5 MOLES PER LITER OF AN ALKALI METAL FERRICYANIDE, .075 TO 1.25 MOLES PER LITER OF AN ALKALI METAL HYDROXIDE AND .00375 TO .045 MOLES PER LITER OF AN ALKALI METAL OXALATE.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US132018A US3098043A (en) | 1961-08-17 | 1961-08-17 | Etchant for molybdenum |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US132018A US3098043A (en) | 1961-08-17 | 1961-08-17 | Etchant for molybdenum |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3098043A true US3098043A (en) | 1963-07-16 |
Family
ID=22452062
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US132018A Expired - Lifetime US3098043A (en) | 1961-08-17 | 1961-08-17 | Etchant for molybdenum |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US3098043A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3532569A (en) * | 1967-03-10 | 1970-10-06 | Gen Motors Corp | Aluminum etchant and process |
| US3639185A (en) * | 1969-06-30 | 1972-02-01 | Ibm | Novel etchant and process for etching thin metal films |
| US4940510A (en) * | 1987-06-01 | 1990-07-10 | Digital Equipment Corporation | Method of etching in the presence of positive photoresist |
| EP0455574A1 (en) * | 1990-04-30 | 1991-11-06 | International Business Machines Corporation | Near neutral pH etching solution for molybdenum or tungsten and method for using it |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1614562A (en) * | 1925-09-05 | 1927-01-18 | Clemens A Laise | Apparatus and method of wire drawing and alloy wires used for radiotubes and other purposes |
| US2077450A (en) * | 1935-01-08 | 1937-04-20 | Alrose Chemical Company | Method and composition for coating iron and steel articles |
| US2566615A (en) * | 1947-03-21 | 1951-09-04 | Sylvania Electric Prod | Etching tungsten coils |
| CA513130A (en) * | 1955-05-24 | Enthone | Dissolving metals |
-
1961
- 1961-08-17 US US132018A patent/US3098043A/en not_active Expired - Lifetime
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA513130A (en) * | 1955-05-24 | Enthone | Dissolving metals | |
| US1614562A (en) * | 1925-09-05 | 1927-01-18 | Clemens A Laise | Apparatus and method of wire drawing and alloy wires used for radiotubes and other purposes |
| US2077450A (en) * | 1935-01-08 | 1937-04-20 | Alrose Chemical Company | Method and composition for coating iron and steel articles |
| US2566615A (en) * | 1947-03-21 | 1951-09-04 | Sylvania Electric Prod | Etching tungsten coils |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3532569A (en) * | 1967-03-10 | 1970-10-06 | Gen Motors Corp | Aluminum etchant and process |
| DE1696138B1 (en) * | 1967-03-10 | 1971-06-16 | Gen Motors Corp | ETC SOLUTION FOR THIN ALUMINUM LAYERS AND USE OF ETC SOLUTION |
| US3639185A (en) * | 1969-06-30 | 1972-02-01 | Ibm | Novel etchant and process for etching thin metal films |
| US4940510A (en) * | 1987-06-01 | 1990-07-10 | Digital Equipment Corporation | Method of etching in the presence of positive photoresist |
| EP0455574A1 (en) * | 1990-04-30 | 1991-11-06 | International Business Machines Corporation | Near neutral pH etching solution for molybdenum or tungsten and method for using it |
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