US5923946A
Expired / Lapsed
US
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Recovery of surface-ready silicon carbide substrates
Assignee: Wolfspeed Inc
•
Filing: 1997-04-17
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Granted: 1999-07-13
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Expires: 2017-04-17
Abstract
Abstract A method is disclosed for recovering surface-ready silicon carbide substrates from heteroepitaxial structures of Group III nitrides on silicon carbide substrates. The method comprises subjecting a Group III nitride epitaxial layer on a silicon carbide substrate to a stress that sufficiently increases the number of dislocations in the epitaxial layer to make the epitaxial layer subject to attack and dissolution in a mineral acid, but that otherwise does not affect the silicon carbide substrate, and thereafter contacting the epitaxial layer with a mineral acid to remove the Group III nitride while leaving the silicon carbide substrate unaffected.
Inventors
- 👤 Gerald H. Negley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 08:09
CPC Classifications
H; H10; H10H; H10H20/00; H10H20/01; H10H20/011; H10H20/013; H10H20/0133; H10H20/01335; Y; Y10; Y10S; Y10S438/00; Y10S438/931
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
95 words
A method of recovering surface-ready silicon carbide substrates from heteroepitaxial structures of Group III nitrides on silicon carbide substrates, the method comprising: subjecting a Group III nitride epitaxial layer on a silicon carbide substrate to a stress that sufficiently increases the number of dislocations in the epitaxial layer to make the epitaxial layer subject to attack and dissolution in a mineral acid, but that otherwise does not affect the silicon carbide substrate; and thereafter contacting the epitaxial layer with a mineral acid to remove the Group III nitride while leaving the silicon carbide substrate unaffected.
Claim 2
Independent Claim
95 words
A method of recovering surface-ready silicon carbide substrates from heteroepitaxial structures of Group III nitrides on silicon carbide substrates, the method comprising: subjecting a Group III nitride epitaxial layer on a silicon carbide substrate to a stress that sufficiently increases the number of dislocations in the epitaxial layer to make the epitaxial layer subject to attack and dissolution in a mineral acid, but that otherwise does not affect the silicon carbide substrate; and thereafter contacting the epitaxial layer with a mineral acid to remove the Group III nitride while leaving the silicon carbide substrate unaffected.
Claim 3
Dependent Claim
30 words
A method according to claim 1 wherein the step of subjecting the Group III nitride layer to stress comprises subjecting a layer of Al x Ga 1-x N to stress.
Claim 4
Dependent Claim
26 words
A method according to claim 1 wherein the step of subjecting the Group III nitride layer to stress comprises subjecting a gallium nitride layer to stress.
Claim 5
Dependent Claim
28 words
A method according to claim 1 wherein the stress step comprises heating the substrate and epitaxial layer to a temperature sufficient to cause the epitaxial layer to dissociate.
Claim 6
Dependent Claim
21 words
A method according to claim 1 wherein the stress step comprises subjecting the substrate and epitaxial layer to rapid thermal annealing.
Claim 7
Dependent Claim
18 words
A method according to claim 5 where in the rapid thermal annealing is carried out at low pressure.
Claim 8
Dependent Claim
21 words
A method according to claim 5 wherein the rapid thermal annealing is carried out in an ambient atmosphere at high temperature.
Claim 9
Dependent Claim
25 words
A method according to claim 1 wherein the step of contacting the epitaxial layer with a mineral acid comprises contacting the layer with phosphoric acid.
Claim 10
Dependent Claim
23 words
A method according to claim 1 wherein the step of subjecting the Group III nitride layer to stress comprises physically abrading the layer.
Claim 11
Dependent Claim
32 words
A method according to claim 1 and further comprising the step of depositing the Group III nitride epitaxial layer on the substrate prior to the step of subjecting the layer to stress.
Claim 12
Independent Claim
102 words
A method of recovering surface-ready silicon carbide substrate from heteroepitaxial structures of Group III nitrides on silicon carbide substrates, the method comprising: depositing a Group III nitride epitaxial layer on silicon carbide substrate; subjecting the Group III nitride epitaxial layer to a stress that sufficiently increases the number of dislocations in the epitaxial layer to make the epitaxial layer subject to attack and dissolution in phosphoric acid, but that otherwise does not affect the silicon carbide substrate; and thereafter contacting the epitaxial layer with hot concentrated phosphoric acid to thereby remove the Group III nitride while leaving the silicon carbide substrate unaffected.
Claim 13
Independent Claim
102 words
A method of recovering surface-ready silicon carbide substrate from heteroepitaxial structures of Group III nitrides on silicon carbide substrates, the method comprising: depositing a Group III nitride epitaxial layer on silicon carbide substrate; subjecting the Group III nitride epitaxial layer to a stress that sufficiently increases the number of dislocations in the epitaxial layer to make the epitaxial layer subject to attack and dissolution in phosphoric acid, but that otherwise does not affect the silicon carbide substrate; and thereafter contacting the epitaxial layer with hot concentrated phosphoric acid to thereby remove the Group III nitride while leaving the silicon carbide substrate unaffected.
Claim 14
Dependent Claim
28 words
A method according to claim 11 wherein the step of depositing the Group III nitride epitaxial layer on the silicon carbide substrate comprises metal organic chemical vapor deposition.
Claim 15
Dependent Claim
41 words
A method according to claim 12 wherein the step of depositing the Group III nitride epitaxial layer on the silicon carbide substrate comprises depositing the Group III nitride from a vapor phase reaction between an organic Group III compound and ammonia.
Claim 16
Dependent Claim
36 words
A method according to claim 12 wherein the step of depositing the Group III nitride epitaxial layer on the silicon carbide substrate comprises depositing gallium nitride from a vapor phase reaction between trimethyl gallium and ammonia.
Claim 17
Dependent Claim
45 words
A method according to claim 11 wherein the step of depositing the Group III nitride epitaxial layer on the silicon carbide substrate further comprises depositing a buffer layer on the silicon carbide substrate prior to the step of depositing the Group III nitride epitaxial layer.
Claim 18
Dependent Claim
26 words
A method according to claim 11 wherein the step of depositing the Group III nitride layer comprises depositing a layer of Al x Ga 1-x N.
Claim 19
Dependent Claim
26 words
A method according to claim 11 wherein the stress step comprises heating the substrate and epitaxial layer to a temperature sufficient to dissociate the epitaxial layer.
Claim 20
Dependent Claim
21 words
A method according to claim 11 wherein the stress step comprises subjecting the substrate and epitaxial layer to rapid thermal annealing.
Claim 21
Dependent Claim
17 words
A method according to claim 18 wherein the rapid thermal annealing is carried out at low pressure.
Claim 22
Dependent Claim
21 words
A method according to claim 18 wherein the rapid thermal annealing is carried out in an ambient atmosphere at high temperature.
Claim 23
Dependent Claim
23 words
A method according to claim 11 wherein the step of subjecting the Group III nitride layer to stress comprises physically abrading the layer.
Claim 24
Dependent Claim
33 words
A method according to claim 11 wherein the step of depositing the Group III nitride layer is selected from the group consisting of molecular beam epitaxy, vapor phase epitaxy, and liquid phase epitaxy.
References Cited (Backward Citations)
JPS50113500A
Cited
US3923567A
Cited
US4009299A
Cited
JPS5343480A
Cited
JPS5687383A
Cited
US4891325A
Cited
JPH02228470A
Cited
US5030536A
Cited
US5131979A
Cited
US5393993A
Cited
US5424254A
Cited
US5523589A
Cited
US5654208A
Cited
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 2002-07-12 | 2003-01-11 | 2003-07-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2006-07-12 | 2007-01-11 | 2007-07-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2010-07-12 | 2011-01-11 | 2011-07-13 | $7700.00 | Window Closed / Lapsed |