US5980265A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Low resistance, stable ohmic contacts to silicon carbide, and method of making the same
Assignee: Wolfspeed Inc
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Filing: 1995-05-23
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Granted: 1999-11-09
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Expires: 2015-05-23
Abstract
Abstract Stable, high temperature electrical contacts to silicon carbide formed using a unique silicide formation process that employs a sacrificial silicon layer between the silicon carbide and the contacting metal, which forms a metal silicide interlayer providing the resulting contact with low specific contact resistance and high electrical and structural stability. The contact interface is formed by reaction below the semiconductor surface, and thus the in-situ silicide formation process is insensitive to surface impurities and oxides and permits the controlled formation of silicides without the formation of excess carbon and carbides at the contact interface. The silicon layer may optionally be doped in situ during growth or implanted with dopants after growth, to lower the contact resistance and enhance its operational stability.
Inventors
- 👤 Michael A. Tischler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 15:07
CPC Classifications
H; H10; H10D; H10D64/00; H10D64/01; H10D64/011; H10D64/0111; H10D64/0115; H10D64/60; H10D64/62; Y; Y10; Y10S; Y10S148/00; Y10S148/148
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
61 words
A method of forming ohmic contacts on a SiC substrate, comprising the steps of: first forming a silicon layer on the SiC substrate; next providing a contact metal on the silicon layer; and then annealing the resulting article for sufficient time and at sufficient temperature to form a metal silicide contact by reaction of the silicon layer with the contact metal.
Claim 2
Independent Claim
61 words
A method of forming ohmic contacts on a SiC substrate, comprising the steps of: first forming a silicon layer on the SiC substrate; next providing a contact metal on the silicon layer; and then annealing the resulting article for sufficient time and at sufficient temperature to form a metal silicide contact by reaction of the silicon layer with the contact metal.
Claim 3
Dependent Claim
18 words
A method according to claim 1, wherein the reaction does not comprise the SiC substrate as a reactant.
Claim 4
Dependent Claim
27 words
A method according to claim 1, wherein said annealing is carried out at a temperature in the range of from about 800° C. to about 1100° C.
Claim 5
Dependent Claim
41 words
A method according to claim 1, wherein the silicon layer is doped with a dopant species selected from the group consisting of p-type dopant atoms and n-type dopant atoms, at a doping concentration of at least 10 18 carriers/cm 3 .
Claim 6
Dependent Claim
33 words
A method according to claim 1, wherein the SiC substrate is grown by vapor deposition of silicon and carbon source reagents, immediately prior to growth of said silicon layer on the SiC substrate.
Claim 7
Dependent Claim
59 words
A method according to claim 5, wherein the SiC substrate is grown by concurrently flowing silicon-containing source reagent and carbon-containing source reagent to a deposition locus at which said growth is carried out, and wherein flow of carbon-containing source reagent is discontinued and flow of silicon-containing source reagent is continued to provide growth of silicon on the SiC substrate.
Claim 8
Dependent Claim
65 words
A method according to claim 1, comprising forming self-aligned contacts on the SiC substrate, by depositing and patterning a dielectric material on the SiC substrate prior to deposition of contact metal, so that upon annealing, a metal silicide forms only where the deposited metal contacts the silicon layer, and etching to remove remaining metal on the patterned dielectric material to leave intact a self-aligned contact.
Claim 9
Dependent Claim
38 words
A method according to claim 1, wherein said step of forming the silicon layer on the SiC substrate comprises a forming method selected from the group consisting of chemical vapor deposition, sputtering, and evaporation from a silicon source.
Claim 10
Dependent Claim
38 words
A method according to claim 1, wherein the step of providing a contact metal on the silicon layer comprises a provision step selected from the group consisting of chemical vapor deposition, sputtering, and evaporation from a metal source.
Claim 11
Dependent Claim
32 words
A method according to claim 1 wherein the silicon layer is doped, by a doping method selected from the group consisting of ion implantation, co-deposition via chemical vapor deposition, sputtering and evaporation.
Claim 12
Independent Claim
78 words
A method of forming ohmic contacts on a SiC substrate comprising the steps of: first forming a silicon layer on the SiC substrate; next providing a contact metal on the silicon layer; and then annealing the resulting article for sufficient time and at sufficient temperature to form a metal silicide contact by reaction of the silicon layer with the contact metal, wherein silicon is the stoichiometrically limiting material in reaction with the contact metal forming said metal silicide.
Claim 13
Independent Claim
78 words
A method of forming ohmic contacts on a SiC substrate comprising the steps of: first forming a silicon layer on the SiC substrate; next providing a contact metal on the silicon layer; and then annealing the resulting article for sufficient time and at sufficient temperature to form a metal silicide contact by reaction of the silicon layer with the contact metal, wherein silicon is the stoichiometrically limiting material in reaction with the contact metal forming said metal silicide.
Claim 14
Dependent Claim
18 words
A method according to claim 1, wherein the metal silicide contact has a resistivity not exceeding 70 micro-ohms-cm.
Claim 15
Dependent Claim
18 words
A method according to claim 1, wherein the metal silicide contact has a resistivity not exceeding 30 micro-ohms-cm.
Claim 16
Dependent Claim
27 words
A method according to claim 1, wherein the metal silicide contact has a specific contact resistance to SiC of less than about 5×10 -5 ohm-cm 2 .
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2002-11-08 | 2003-05-10 | 2003-11-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2006-11-08 | 2007-05-10 | 2007-11-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2010-11-08 | 2011-05-10 | 2011-11-09 | $7700.00 | Window Closed / Lapsed |