WO1981000932A1 - Ohmic contact to p-type inp or ingaasp - Google Patents
Ohmic contact to p-type inp or ingaasp Download PDFInfo
- Publication number
- WO1981000932A1 WO1981000932A1 PCT/US1980/001079 US8001079W WO8100932A1 WO 1981000932 A1 WO1981000932 A1 WO 1981000932A1 US 8001079 W US8001079 W US 8001079W WO 8100932 A1 WO8100932 A1 WO 8100932A1
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- WO
- WIPO (PCT)
- Prior art keywords
- layer
- beryllium
- gold
- ohmic contact
- nanometers
- Prior art date
Links
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims abstract description 31
- 239000010931 gold Substances 0.000 claims abstract description 20
- 239000004065 semiconductor Substances 0.000 claims abstract description 20
- 238000000034 method Methods 0.000 claims abstract description 13
- 239000000463 material Substances 0.000 claims abstract description 12
- 229910052763 palladium Inorganic materials 0.000 claims abstract description 12
- HOHAQBNFPZHTJB-UHFFFAOYSA-N beryllium gold Chemical compound [Be].[Au] HOHAQBNFPZHTJB-UHFFFAOYSA-N 0.000 claims abstract description 11
- 229910052737 gold Inorganic materials 0.000 claims abstract description 11
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000010438 heat treatment Methods 0.000 claims abstract description 3
- 238000000151 deposition Methods 0.000 claims description 10
- 229910052790 beryllium Inorganic materials 0.000 claims description 8
- ATBAMAFKBVZNFJ-UHFFFAOYSA-N beryllium atom Chemical compound [Be] ATBAMAFKBVZNFJ-UHFFFAOYSA-N 0.000 claims description 7
- 229910052751 metal Inorganic materials 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 4
- 150000001875 compounds Chemical class 0.000 description 10
- 239000000758 substrate Substances 0.000 description 9
- 238000005275 alloying Methods 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 6
- 230000008021 deposition Effects 0.000 description 5
- 239000002019 doping agent Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000001465 metallisation Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 229910018731 Sn—Au Inorganic materials 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- YTQAOBAJRIBHLX-UHFFFAOYSA-N germanium palladium Chemical compound [Pd]=[Ge] YTQAOBAJRIBHLX-UHFFFAOYSA-N 0.000 description 1
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 1
- 238000004943 liquid phase epitaxy Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 229910052762 osmium Inorganic materials 0.000 description 1
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229910002059 quaternary alloy Inorganic materials 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- 239000010948 rhodium Substances 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 238000005389 semiconductor device fabrication Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000001771 vacuum deposition Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/40—Electrodes ; Multistep manufacturing processes therefor
- H01L29/43—Electrodes ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
- H01L29/45—Ohmic electrodes
- H01L29/452—Ohmic electrodes on AIII-BV compounds
-
- 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
- H01L21/285—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation
- H01L21/28506—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers
- H01L21/28575—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers on semiconductor bodies comprising AIIIBV compounds
Definitions
- This invention is concerned with a method of making ohmic contacts to p-type InP and InGaAsP, and to semiconductor devices having such contacts.
- the contacting material may form a rectifying : rather than ohmic, contact with the semiconductor material , or it may not reliably bond to the semiconductor material, and physically unreliable electrical contacts result.
- Group III-V semiconductor compounds are of much interest today, and much- effort has been directed toward developing reliable ohmic contacts with such compounds.
- Many processes for fabricating low resistance ohmic contacts to such compounds are known. These processes typically involve the deposition of one or more layers and may or may not involve one or more heat treating steps.
- U.S. Patent 3,214,654 describes ohmic contacts to Group III-V compounds which are formed by a layer of a metal selected from the group consisting of silver, gold, ruthenium, rhodium, palladium, osmium, irridium and platinum and a layer of either nickel or cobalt. Germanium-palladium contacts to n-type Group III-V compounds are described by U.S. Patent 4,011,583. Particular interest has recently been shown in
- Group III-V compounds that are useful in optical devices, such as light emitting diodes, lasers and photodetectors , that operate at wavelengths longer than 1.00 micrometers.
- the term "light,” as used in this specification includes both the visible and the near infrared portions of the electromagnetic spectrum. Interest in devices that operate in this region has arisen primarily because the silica-based optical fiber compositions presently contemplated for optical communication systems have smaller material dispersion, as well as low loss, about 1.00 micrometer than they do below 1.00 micrometer.
- One class of light emitting devices presently contemplated for such systems uses the quaternary alloy, InGaAsP, which is grown on InP. Such devices are useful between 0.95ym and 1.68 ⁇ m. These light emitting devices operate at high forward current and require high quality ohmic contacts to reduce series resistance. For this class of devices, as well as others, ohmic contacts to InP are necessary.
- Ohmic contacts to some Group III-V compounds using Be-Au metallizations, i.e. , Be is used as the acceptor, are known.
- Be is used as the acceptor
- Such metallizations have been made to p-type GaP.
- formation of these ohmic contacts has required heating the GaP devices to the
- V relatively high temperature of 600 degrees C for approximately 5 minutes to form the ohmic contact. Alloying temperatures of 600 degrees C cannot be used to form ohmic contacts to either InP or InP containing devices because InP begins to decompose through P outdiffusion at approximately 400 degrees.
- ohmic contacts having low resistance can be made to p-type InP material in a semiconductor device by using beryllium as the acceptor.
- the contact is formed by sequentially depositing, on the InP, a 1 to 3 percent, by weight, beryllium in gold (Be-Au) composition and a gold overlay.
- Be-Au gold
- the ⁇ depositi on is followed by heat treating the deposited material at a temperature less than 440 degrees C for a time of at least 1 minute.
- Deposition of a palladium layer on the InP layer prior to the deposition of the Be-Au layer permits use of a heat treating temperature less than 420 degrees C but generally results in a contact with a slightly higher resistance.
- This method may also be used to produce a low resistance ohmic contact to p-type InGaAsP.
- FIG. 1 is a cross-sectional view of a device processed according to this invention.
- FIG. 2 plots alloying temperature, horizontally, versus resistance in ohms, vertically, for a contact of this invention
- FIG. 3 plots alloyint time, horizontally, versus resistance in ohms, vertically, for a contact of this invention.
- FIG. 1 shows a semiconductor device having a semiconductor layer 10.
- Layer 10 may be a substrate, but is more typically an epitaxial layer grown on a substrate.
- the sem conductor device may be a light emitting diode, laser, etc.
- Metal layers 20, 30 and 40 are sequentially
- the semiconductor device further comprises additional semiconductor materials (not shown) deposited on layer 10 opposite layer 20.
- Layer 10 consists of InP.
- Layer 20 consists of palladium
- layer 30 consists of a beryllium-gold composition
- layer 40 consists of gold.
- the InP layer may be covered with an InGaAsP layer prior to deposition of layer 20, in which case the ohmic contact is made to the InGaAsP layer.
- Conventional techniques, such as electron gun evaporation may be used to deposit the layers.
- Beryllium has a vapor pressure very similar to that of gold and can, therefore, be evaporated very reproducibly from beryllium-gold sources. Pressures are
- p-type dopants may be used in the InP substrate.
- Zn Zn
- concentration a concentration of a compound having a high degree of p-type dopants
- 18 -3 of 8x10 cm may be used in a liquid-encapsulated
- Layer 20 is optional and when present, is approximately 100A C O nanometers) thick.
- a layer of 100A (10 nanometers) is sufficiently thick to trap outdiffusing P through formation of intermetallic P-Pd compounds without impeding Be migration into the InP substrate. Thicker layers may result in the formation of undesired Pd compounds.
- This layer permits, as sub ⁇ sequently described, lowering of the heat treating or alloying temperature and, therefore, reduction of the InP tendency for thermal dissociation. There may, however,
- Layer 30 consists of a gold beryllium composition having between 1 and 3 percent, by weight, beryllium.
- the described weight percent range of Be is desirable because Be and Au form well-defingd structures within this range.
- Layer 30 is typically 800A 80 nanometers) thick, although thicknesses as small as 600A (60 nanometers) and as large as 1000A (100 nanometers) may be used. Below 600A, (60 nanometers) thgre may not be sufficient Be for the reaction, and above 1000A, (100 nanometers) too much Be may be present. The presence of too much Be makes contact formation difficult as the reaction is driven by Au.
- a Be content of 3 percent is preferred over 1 percent because at the lower weight percent, contact uniformly is not as good.
- Gold layer 40 is at least 2100A (210 nanometers) thick and may be thicker if so desired. However, if layer 40 is thinner, the contact may not be uniform and smooth after heat treating. The minimum thickness is conveniently used.
- the structure is heat-treated at a temperature less than 440 degrees C for a residence time of at least 1 minute.
- the preferred range for heat treat- -ing is between 400 degrees C and 440 degrees C, and the residence time is between 5 and 10 minutes.
- the alloying temperature is preferably less than 420 degrees C, and the residence time is at least 1 minute.
- the preferred heat treating temperature is approximately- 400 degrees C. Temperatures outside the above range have higher contact resistances, and are, therefore, less preferred.
- Heat treating conveniently takes place in any of the conventionally used atmospheres such as forming gas (a hydrogen-nitrogen mixture), argon or nitrogen.
- Alloying or heat treating times and temperatures may be determined with more specificity by reference to FIGS. 2 and 3 which show the measured resistance as functions of treating temperatures and times, respectively.
- FIG. 2 plots alloying temperature in degrees centigrade, horizontally, versus resistance in ohms, vertically, for contacts having an 800A (80 nanometers) thick 3 weight percent Be in Au layer, and a 2100A (210 nanometers thick Au Q layer.
- the open circles represent contacts with a 100A (10 nanometers) thick Pd layer, and the solid circles represent contacts in which a
- Pd layer was not present.
- the contacts were alloyed for 10 minutes.
- the contact resistances are a minimum between 400 and 440 degrees C without the Pd layer. With the Pd layer present, temperatures equal to or above 375 degrees C may be used.
- the palladium layer traps outdiffusing phosphorous and forms intermetal 1 i c palladium-phosphorous compounds.
- the resistance obtained by this scheme is generally slightly greater than that obtained without the palladium layer.
- the ohmic contact can be formed adequately, i.e. , with an acceptably small resistance, at a temperature as low as 375 degrees C compared to the approximately 400 degrees C needed if the palladium layer is not present. At 375 and 400 degrees C, the resistances are approximately 10 and 5 ohms, respectively.
- FIG. 3 plots alloying time in minutes, horizontally, versus resistance in ohms, vertically, for contacts having an 800A (80 nanometers) 3 weight percent Be in Au layer and a 2100A (210 nanometers) Au layer.
- the contacts were alloyed at 420 degrees C.
- the contact resistances are a minimum for alloying times between 5 and 10 minutes. Heat treating times outside this range lead to higher resistances, especially for shorter times. Longer times are not preferred because of the increased possibility that undesired i ntermetal li c compounds may be formed in addition to the possibility of InP decompo ⁇ sition.
- a double heterostructure InP/InGaAsP/InP light emitting diode was grown by liquid phase epitaxy on a (100) oriented n-type InP substrate and consisted of a buffer layer approximately 2 micro-
Abstract
Semiconductor device comprising a p-type InP or InGaAsP semiconductor material and an ohmic contact to a surface of the semiconductor material and a process for producing the same. The ohmic contact includes, in succession from the said surface, a layer of beryllium gold and a layer of gold. The surface containing the layers is heat-treated at a temperature of 440 C or less for a residence time of at least one minute. Optionally, a layer of palladium may be positioned intermediate the surface and the beryllium-gold layer permitting heat treatment at lower temperatures e.g., less than 420 C.
Description
Ohmic Contact To P-Type InP or InGaAsP
Technical Field
This invention is concerned with a method of making ohmic contacts to p-type InP and InGaAsP, and to semiconductor devices having such contacts. Background of the Invention
Successful semiconductor device fabrication and operation frequently requires contacting the semiconductor device with low resistance ohmic contacts. Problems often arise in attempting to fabricate and use such contacts. For example, the contacting material may form a rectifying: rather than ohmic, contact with the semiconductor material , or it may not reliably bond to the semiconductor material, and physically unreliable electrical contacts result.
Group III-V semiconductor compounds are of much interest today, and much- effort has been directed toward developing reliable ohmic contacts with such compounds. Many processes for fabricating low resistance ohmic contacts to such compounds are known. These processes typically involve the deposition of one or more layers and may or may not involve one or more heat treating steps. U.S. Patent 3,214,654 describes ohmic contacts to Group III-V compounds which are formed by a layer of a metal selected from the group consisting of silver, gold, ruthenium, rhodium, palladium, osmium, irridium and platinum and a layer of either nickel or cobalt. Germanium-palladium contacts to n-type Group III-V compounds are described by U.S. Patent 4,011,583. Particular interest has recently been shown in
Group III-V compounds that are useful in optical devices, such as light emitting diodes, lasers and photodetectors , that operate at wavelengths longer than 1.00 micrometers. It should be understood that the term "light," as used in this specification, includes both the visible and the
near infrared portions of the electromagnetic spectrum. Interest in devices that operate in this region has arisen primarily because the silica-based optical fiber compositions presently contemplated for optical communication systems have smaller material dispersion, as well as low loss, about 1.00 micrometer than they do below 1.00 micrometer.
One class of light emitting devices presently contemplated for such systems uses the quaternary alloy, InGaAsP, which is grown on InP. Such devices are useful between 0.95ym and 1.68μm. These light emitting devices operate at high forward current and require high quality ohmic contacts to reduce series resistance. For this class of devices, as well as others, ohmic contacts to InP are necessary.
While low resistance ohmic contacts to n-type InP can now be easily fabricated, the formation of ohmic contacts to p-type InP still presents difficulties. P-type contacts to InP have been made using Zn as the acceptor. While these contacts are quite acceptable for many purposes, they have a number of drawbacks. For example,
Journal of Applied Physics, 46, pp. 452-453 (1975)
-3 2 reports a rather high resistance, namely, 10 ohm. cm , for an electroplated Au/Zn/Au metallization. Furthermore, additional problems arise when Zn is used as the acceptor because the relative volatility of Zn makes it difficult to fabricate the contact with vacuum deposition techniques.
Moreover, rapid diffusion of the Zn through the InP, together with the high doping concentrations required, may cause either junction motion or long-term device reliability problems or both.
Ohmic contacts to some Group III-V compounds using Be-Au metallizations, i.e. , Be is used as the acceptor, are known. For example, such metallizations have been made to p-type GaP. However, formation of these ohmic contacts has required heating the GaP devices to the
C.
V
relatively high temperature of 600 degrees C for approximately 5 minutes to form the ohmic contact. Alloying temperatures of 600 degrees C cannot be used to form ohmic contacts to either InP or InP containing devices because InP begins to decompose through P outdiffusion at approximately 400 degrees. Summary of the Invention
We have found that ohmic contacts having low resistance can be made to p-type InP material in a semiconductor device by using beryllium as the acceptor. The contact is formed by sequentially depositing, on the InP, a 1 to 3 percent, by weight, beryllium in gold (Be-Au) composition and a gold overlay. The^ depositi on is followed by heat treating the deposited material at a temperature less than 440 degrees C for a time of at least 1 minute. Deposition of a palladium layer on the InP layer prior to the deposition of the Be-Au layer permits use of a heat treating temperature less than 420 degrees C but generally results in a contact with a slightly higher resistance. This method may also be used to produce a low resistance ohmic contact to p-type InGaAsP. Brief Description of the Drawing
FIG. 1 is a cross-sectional view of a device processed according to this invention.
FIG. 2 plots alloying temperature, horizontally, versus resistance in ohms, vertically, for a contact of this invention; and
FIG. 3 plots alloyint time, horizontally, versus resistance in ohms, vertically, for a contact of this invention. Detailed Description
FIG. 1 shows a semiconductor device having a semiconductor layer 10. Layer 10 may be a substrate, but is more typically an epitaxial layer grown on a substrate. The sem conductor device may be a light emitting diode, laser, etc. Metal layers 20, 30 and 40 are sequentially
Q.*-PI_ IPO
deposited above layer 10 and form the ohmic contact after heat treating. The semiconductor device further comprises additional semiconductor materials (not shown) deposited on layer 10 opposite layer 20. Layer 10 consists of InP. Layer 20 consists of palladium, layer 30 consists of a beryllium-gold composition, and layer 40 consists of gold. For reasons that will be explained, the presence of layer 20 is optional. If layer 20 is omitted, layer 30 is deposited directly on the substrate. The InP layer may be covered with an InGaAsP layer prior to deposition of layer 20, in which case the ohmic contact is made to the InGaAsP layer. Conventional techniques, such as electron gun evaporation, may be used to deposit the layers. Beryllium has a vapor pressure very similar to that of gold and can, therefore, be evaporated very reproducibly from beryllium-gold sources. Pressures are
-5 desirably held below 6x10 torr.
Conventional p-type dopants may be used in the InP substrate. For example, Zn , with a concentration
18 -3 of 8x10 cm may be used in a liquid-encapsulated
Czochralski (LEC) grown substrate. The particular p-type dopant used is not critical to formation of an ohmic contact with this invention. The dopant concentration
17 -3 should, however, be at least 10 cm to form an ohmic contact. The dopant concentration should be as high as is practical because resistance decreases as the dopant concentration increases. The method of substrate growth and the substrate orientation are both noncritical. Layer 20 is optional and when present, is approximately 100A C O nanometers) thick. A layer of 100A (10 nanometers) is sufficiently thick to trap outdiffusing P through formation of intermetallic P-Pd compounds without impeding Be migration into the InP substrate. Thicker layers may result in the formation of undesired Pd compounds. This layer permits, as sub¬ sequently described, lowering of the heat treating or alloying temperature and, therefore, reduction of the InP tendency for thermal dissociation. There may, however,
-
be a slight increase in contact resistance when the Pd layer is present.
Layer 30 consists of a gold beryllium composition having between 1 and 3 percent, by weight, beryllium. The described weight percent range of Be is desirable because Be and Au form well-defingd structures within this range. Layer 30 is typically 800A 80 nanometers) thick, although thicknesses as small as 600A (60 nanometers) and as large as 1000A (100 nanometers) may be used. Below 600A, (60 nanometers) thgre may not be sufficient Be for the reaction, and above 1000A, (100 nanometers) too much Be may be present. The presence of too much Be makes contact formation difficult as the reaction is driven by Au. A Be content of 3 percent is preferred over 1 percent because at the lower weight percent, contact uniformly is not as good.
Gold layer 40 is at least 2100A (210 nanometers) thick and may be thicker if so desired. However, if layer 40 is thinner, the contact may not be uniform and smooth after heat treating. The minimum thickness is conveniently used.
After deposition of the layers, the structure is heat-treated at a temperature less than 440 degrees C for a residence time of at least 1 minute. If the palladium layer is not present, the preferred range for heat treat- -ing is between 400 degrees C and 440 degrees C, and the residence time is between 5 and 10 minutes. If palladium layer 20. is present, the alloying temperature is preferably less than 420 degrees C, and the residence time is at least 1 minute. The preferred heat treating temperature is approximately- 400 degrees C. Temperatures outside the above range have higher contact resistances, and are, therefore, less preferred.
Heat treating conveniently takes place in any of the conventionally used atmospheres such as forming gas (a hydrogen-nitrogen mixture), argon or nitrogen.
Alloying or heat treating times and temperatures may be determined with more specificity by reference to
FIGS. 2 and 3 which show the measured resistance as functions of treating temperatures and times, respectively.
FIG. 2 plots alloying temperature in degrees centigrade, horizontally, versus resistance in ohms, vertically, for contacts having an 800A (80 nanometers) thick 3 weight percent Be in Au layer, and a 2100A (210 nanometers thick AuQlayer. The open circles represent contacts with a 100A (10 nanometers) thick Pd layer, and the solid circles represent contacts in which a
Pd layer was not present. The contacts were alloyed for 10 minutes. The contact resistances are a minimum between 400 and 440 degrees C without the Pd layer. With the Pd layer present, temperatures equal to or above 375 degrees C may be used.
It is hypothesized that lower heat treating temperatures can be used with the palladium layer because the palladium layer traps outdiffusing phosphorous and forms intermetal 1 i c palladium-phosphorous compounds. The resistance obtained by this scheme is generally slightly greater than that obtained without the palladium layer. However, the ohmic contact can be formed adequately, i.e. , with an acceptably small resistance, at a temperature as low as 375 degrees C compared to the approximately 400 degrees C needed if the palladium layer is not present. At 375 and 400 degrees C, the resistances are approximately 10 and 5 ohms, respectively.
FIG. 3 plots alloying time in minutes, horizontally, versus resistance in ohms, vertically, for contacts having an 800A (80 nanometers) 3 weight percent Be in Au layer and a 2100A (210 nanometers) Au layer. The contacts were alloyed at 420 degrees C. The contact resistances are a minimum for alloying times between 5 and 10 minutes. Heat treating times outside this range lead to higher resistances, especially for shorter times. Longer times are not preferred because of the increased possibility that undesired i ntermetal li c compounds may
be formed in addition to the possibility of InP decompo¬ sition.
E-xample: A double heterostructure InP/InGaAsP/InP light emitting diode was grown by liquid phase epitaxy on a (100) oriented n-type InP substrate and consisted of a buffer layer approximately 2 micro-
18 -3 meters thick Sn doped, (n = 10 cm" ), a 1-micrometer
16 - ~ thick active InGaAsPlayer (n - 2 x 10 cm ), and a
18 — ~l Zn-doped (n = 10 cm" ) p-type InP layer having thickness of 1.5 micrometers. An ohmic contact was made to the p-type layer as described above. The contact was a 50 micrometer dot. The contact to the n-type layer was a horseshoe-shaped sandwich of Au-Sn-Au about 5000A (500 nanometers) thick. At a current of 60 mA and a forward voltage of approximately 1.5 eV, and power emitted into the air was approximately 3 mW. This corresponds to a power conversion efficiency of approximately 3 percent. The upper limit of specific contact resistance
-5 was 7.8 x 10 ohm. cm. This value is approximately two orders of magnitude lower than specific resistances previously reported for Au-Zn contacts to InP.
Claims
1. A semiconductor device comprising a p-type InP or InGaAsP semiconductor material and an ohmic contact to a surface of the semiconductor material, CHARACTERIZED IN THAT said ohmic contact includes, in succession from the said surface, a layer of beryllium-gold and a layer of gold.
2. A semiconductor device according to claim 1, CHARACTERIZED IN THAT said ohmic contact further comprises a layer of palladium intermediate the said surface and the beryllium-gold layer.
3. A semiconductor device according to claim 1, or 2,
CHARACTERIZED IN THAT said beryllium-gold layer contains prior to a heat treatment, from 1 to 3 weight percent of beryllium.
4. A method of producing an ohmic contact to a semiconductor device, which comprises a p-type InP or
InGaAsP semiconductor materially depositing at least one metal layer on a surface of the material and heat treating the device,
CHARACTERIZED IN THAT said at least one metal layer includes, in succession from the surface, a layer of beryllium-gold and a layer of gold, and the said heat treating is conducted at a temperature of 440° C or less for a resistance time of at least one minute.
5. A method according to claim 4,
CHARACTERIZED BY
■using a beryllium-gold layer containing from 1 to 3 weight percent of beryllium.
6. A method according to claim 5, CHARACTERIZED BY depositing said beryllium-gold layer in a thickness of from 60 to 100 nanometers (600 to 1000A) preferably 80 nanometers (800A).
7. A method according to claim 4, CHARACTERIZED BY conducting said heat treating at a temperature ranging from 400 to 440 degrees C.
8. A method according to claim 4, CHARACTERIZED BY optionally depositing upon said surface and prior to said beryllium-gold layer, a palladium layer approximately 10 nanometers (100A) thick.
9. A method according to claim 8, CHARACTERIZED BY conducting said heat treating at a temperature ranging from 375 and 420 degrees C, preferably at a temperature of 400 degrees C.
10. A method according to any one of preceding claims 4, 5, 6, 7, 8 or 9,
CHARACTERIZED BY depositing said goldo layer in a thickness of at least 210 nanometers C2100A).
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE8080901830T DE3071336D1 (en) | 1979-09-27 | 1980-08-22 | Ohmic contact to p-type inp or ingaasp |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US79451 | 1979-09-27 | ||
US06/079,451 US4366186A (en) | 1979-09-27 | 1979-09-27 | Ohmic contact to p-type InP |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1981000932A1 true WO1981000932A1 (en) | 1981-04-02 |
Family
ID=22150652
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1980/001079 WO1981000932A1 (en) | 1979-09-27 | 1980-08-22 | Ohmic contact to p-type inp or ingaasp |
Country Status (5)
Country | Link |
---|---|
US (1) | US4366186A (en) |
EP (1) | EP0037401B1 (en) |
JP (1) | JPH0139206B2 (en) |
DE (1) | DE3071336D1 (en) |
WO (1) | WO1981000932A1 (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0413491A2 (en) * | 1989-08-16 | 1991-02-20 | AT&T Corp. | Method of making a semiconductor device |
EP0424857A2 (en) * | 1989-10-23 | 1991-05-02 | Sumitomo Electric Industries, Ltd. | Process for producing ohmic electrode for p-type cubic system boron nitride |
US5187560A (en) * | 1989-11-28 | 1993-02-16 | Sumitomo Electric Industries, Ltd. | Ohmic electrode for n-type cubic boron nitride and the process for manufacturing the same |
US5240877A (en) * | 1989-11-28 | 1993-08-31 | Sumitomo Electric Industries, Ltd. | Process for manufacturing an ohmic electrode for n-type cubic boron nitride |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4414561A (en) * | 1979-09-27 | 1983-11-08 | Bell Telephone Laboratories, Incorporated | Beryllium-gold ohmic contact to a semiconductor device |
US4471005A (en) * | 1983-01-24 | 1984-09-11 | At&T Bell Laboratories | Ohmic contact to p-type Group III-V semiconductors |
US4816881A (en) * | 1985-06-27 | 1989-03-28 | United State Of America As Represented By The Secretary Of The Navy | A TiW diffusion barrier for AuZn ohmic contacts to p-type InP |
US5015603A (en) * | 1988-06-17 | 1991-05-14 | The United States Of America As Represented By The Secretary Of The Navy | TiW diffusion barrier for AuZn ohmic contact to P-Type InP |
JPH04154511A (en) * | 1990-10-15 | 1992-05-27 | Kawasaki Steel Corp | Method and device for packaging ring |
US5100835A (en) * | 1991-03-18 | 1992-03-31 | Eastman Kodak Company | Shallow ohmic contacts to N-GaAs |
TW456058B (en) * | 2000-08-10 | 2001-09-21 | United Epitaxy Co Ltd | Light emitting diode and the manufacturing method thereof |
US9065010B2 (en) * | 2011-06-28 | 2015-06-23 | Universal Display Corporation | Non-planar inorganic optoelectronic device fabrication |
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1979
- 1979-09-27 US US06/079,451 patent/US4366186A/en not_active Expired - Lifetime
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1980
- 1980-08-22 JP JP55502160A patent/JPH0139206B2/ja not_active Expired
- 1980-08-22 DE DE8080901830T patent/DE3071336D1/en not_active Expired
- 1980-08-22 WO PCT/US1980/001079 patent/WO1981000932A1/en active IP Right Grant
-
1981
- 1981-04-08 EP EP80901830A patent/EP0037401B1/en not_active Expired
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US3214654A (en) * | 1961-02-01 | 1965-10-26 | Rca Corp | Ohmic contacts to iii-v semiconductive compound bodies |
US3942244A (en) * | 1967-11-24 | 1976-03-09 | Semikron Gesellschaft Fur Gleichrichterbau Und Elektronik M.B.H. | Semiconductor element |
US3598997A (en) * | 1968-07-05 | 1971-08-10 | Gen Electric | Schottky barrier atomic particle and x-ray detector |
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US3768151A (en) * | 1970-11-03 | 1973-10-30 | Ibm | Method of forming ohmic contacts to semiconductors |
US3987480A (en) * | 1973-05-18 | 1976-10-19 | U.S. Philips Corporation | III-V semiconductor device with OHMIC contact to high resistivity region |
US4011583A (en) * | 1974-09-03 | 1977-03-08 | Bell Telephone Laboratories, Incorporated | Ohmics contacts of germanium and palladium alloy from group III-V n-type semiconductors |
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Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0413491A2 (en) * | 1989-08-16 | 1991-02-20 | AT&T Corp. | Method of making a semiconductor device |
US5036023A (en) * | 1989-08-16 | 1991-07-30 | At&T Bell Laboratories | Rapid thermal processing method of making a semiconductor device |
EP0413491A3 (en) * | 1989-08-16 | 1993-10-06 | American Telephone And Telegraph Company | Method of making a semiconductor device |
EP0424857A2 (en) * | 1989-10-23 | 1991-05-02 | Sumitomo Electric Industries, Ltd. | Process for producing ohmic electrode for p-type cubic system boron nitride |
US5057454A (en) * | 1989-10-23 | 1991-10-15 | Sumitomo Electric Industries, Ltd. | Process for producing ohmic electrode for p-type cubic system boron nitride |
EP0424857A3 (en) * | 1989-10-23 | 1993-06-30 | Sumitomo Electric Industries, Ltd. | Process for producing ohmic electrode for p-type cubic system boron nitride |
US5187560A (en) * | 1989-11-28 | 1993-02-16 | Sumitomo Electric Industries, Ltd. | Ohmic electrode for n-type cubic boron nitride and the process for manufacturing the same |
US5240877A (en) * | 1989-11-28 | 1993-08-31 | Sumitomo Electric Industries, Ltd. | Process for manufacturing an ohmic electrode for n-type cubic boron nitride |
Also Published As
Publication number | Publication date |
---|---|
EP0037401A1 (en) | 1981-10-14 |
JPH0139206B2 (en) | 1989-08-18 |
EP0037401A4 (en) | 1983-07-26 |
US4366186A (en) | 1982-12-28 |
JPS56501227A (en) | 1981-08-27 |
DE3071336D1 (en) | 1986-02-20 |
EP0037401B1 (en) | 1986-01-08 |
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