Patent US5454915A successfully refreshed from Google Patents.
US5454915A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of fabricating porous silicon carbide (SiC)
Assignee: Kulite Semiconductor Products Inc
•
Filing: 1993-09-01
•
Granted: 1995-10-03
•
Expires: 2013-09-01
Abstract
Abstract Porous silicon carbide is fabricated according to techniques which result in a significant portion of nanocrystallites within the material in a sub 10 nanometer regime. There is described techniques for passivating porous silicon carbide which result in the fabrication of optoelectronic devices which exhibit brighter blue luminescence and exhibit improved qualities. Based on certain of the techniques described porous silicon carbide is used as a sacrificial layer for the patterning of silicon carbide. Porous silicon carbide is then removed from the bulk substrate by oxidation and other methods. The techniques described employ a two-step process which is used to pattern bulk silicon carbide where selected areas of the wafer are then made porous and then the porous layer is subsequently removed. The process to form porous silicon carbide exhibits dopant selectivity and a two-step etching procedure is implemented for silicon carbide multilayers.
Inventors
- 👤 Joseph S. Shor
- 👤 Anthony D. Kurtz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 12:42
CPC Classifications
H; H10; H10H; H10H20/00; H10H20/80; H10H20/81; H10H20/822; H10H20/826; H10D; H10D62/00; H10D62/80; H10D62/83; H10D62/832; H10D62/8325; H10D8/00; H10H20/01; H10H20/011; H10H20/014; H10P; H10P50/00; H10P50/20; H10P52/00; H10P95/00; H10P95/70; H10W; H10W10/00; H10W10/01; Y; Y10; Y10S; Y10S438/00; Y10S438/96
Claims Analysis
Total Claims: 38
Claim 1
Independent Claim
50 words
A method of fabricating porous SiC comprising the steps of: placing a wafer of silicon carbide in a electrochemical cell; electrochemically etching said wafer for a period sufficient to form pores on a exposed surface of said wafer; and illuminating said exposed surface of said wafer with ultraviolet (UV) light.
Claim 2
Independent Claim
50 words
A method of fabricating porous SiC comprising the steps of: placing a wafer of silicon carbide in a electrochemical cell; electrochemically etching said wafer for a period sufficient to form pores on a exposed surface of said wafer; and illuminating said exposed surface of said wafer with ultraviolet (UV) light.
Claim 3
Dependent Claim
12 words
The method according to claim 1, wherein said wafer is n-type SiC.
Claim 4
Dependent Claim
25 words
The method according to claim 2, wherein said n-type SiC has a carrier concentration of about 3×10 18 /cm 3 with said SiC being 6H-SiC.
Claim 5
Dependent Claim
12 words
The method according to claim 1 wherein said wafer is p-type SiC.
Claim 6
Dependent Claim
23 words
The method according to claim 4, wherein said p-type SiC has a carrier concentration of between 2 to 3×10 18 /cm 3 .
Claim 7
Dependent Claim
33 words
The method according to claim 5, wherein said step of electrochemically etching includes applying an anodic potential of from 2 to 3 V at a saturated reference electrode for 1 to 60 minutes.
Claim 8
Dependent Claim
25 words
The method according to claim 1, wherein the intensity of said UV light is between 50-500 mW/cm 3 and the wavelength is between 250-400 nanometers.
Claim 9
Dependent Claim
23 words
The method according to claim 1, wherein said step of electrochemically etching includes applying an anodic potential to said wafer in said cell.
Claim 10
Dependent Claim
13 words
The method according to claim 8, wherein said potential is between 0-3 volts.
Claim 11
Dependent Claim
13 words
The method according to claim 1, wherein said etching employs hydrofluoric acid (HF).
Claim 12
Dependent Claim
13 words
The method according to claim 10, wherein said HF is 2.5% in water.
Claim 13
Dependent Claim
27 words
The method according to claim 1, further including oxidizing porous portions of said wafer after said etching step to convert said porous silicon carbide into silicon dioxide.
Claim 14
Dependent Claim
14 words
The method according to claim 12, further including densifying the regions of silicon dioxide.
Claim 15
Dependent Claim
17 words
The method according to claim 13, wherein said densifying step comprises annealing said regions of silicon dioxide.
Claim 16
Dependent Claim
17 words
The method according to claim 1, wherein pores of submicron dimensions are formed during said etching step.
Claim 17
Dependent Claim
20 words
The method according to claim 1, wherein a monocrystalline layer of porous silicon carbide is formed during said etching step.
Claim 18
Dependent Claim
15 words
The method according to claim 1, wherein said pores spacings are less than 10 nm.
Claim 19
Dependent Claim
17 words
The method according to claim 1, further including the step of passivating a surface of said layer.
Claim 20
Dependent Claim
24 words
The method according to claim 18, wherein said passivating step comprises forming a thin insulating layer on the surface of the said porous layer.
Claim 21
Dependent Claim
45 words
A process for etching silicon carbide comprising: providing a substrate or epilayer of silicon carbide, said silicon carbide being of a first conductivity type; selectively anodizing said substrate electrochemically to form porous regions of silicon carbide thereon; and removing said porous regions from said substrate.
Claim 22
Dependent Claim
45 words
A process for etching silicon carbide comprising: providing a substrate or epilayer of silicon carbide, said silicon carbide being of a first conductivity type; selectively anodizing said substrate electrochemically to form porous regions of silicon carbide thereon; and removing said porous regions from said substrate.
Claim 23
Dependent Claim
20 words
The process according to claim 20, further including the step of oxidizing said porous regions prior to said removing step.
Claim 24
Dependent Claim
56 words
An etch stop process comprising the steps of: providing a SiC layer of a first conductivity type, on top of a layer of SiC of a second conductivity type; and anodizing the first layer so that the second layer remains inert, to form porous SiC in place of the first layer; and removing the porous layer.
Claim 25
Dependent Claim
56 words
An etch stop process comprising the steps of: providing a SiC layer of a first conductivity type, on top of a layer of SiC of a second conductivity type; and anodizing the first layer so that the second layer remains inert, to form porous SiC in place of the first layer; and removing the porous layer.
Claim 26
Dependent Claim
18 words
The process according to claim 22, wherein said porous regions are defined photolithographically prior to said anodizing step.
Claim 27
Dependent Claim
15 words
The process to claim 2 for providing a heterojunction of porous SiC and non-porous SiC.
Claim 28
Independent Claim
48 words
A method of fabricating porous SiC comprising the steps of: placing a wafer of silicon carbide in a electrochemical cell; electrochemically etching said wafer for a period sufficient to form pores on a exposed surface of said wafer wherein said pores define spacings of less than 1 micron.
Claim 29
Independent Claim
48 words
A method of fabricating porous SiC comprising the steps of: placing a wafer of silicon carbide in a electrochemical cell; electrochemically etching said wafer for a period sufficient to form pores on a exposed surface of said wafer wherein said pores define spacings of less than 1 micron.
Claim 30
Dependent Claim
22 words
The method according to claim 25 further including the step of: illuminating said exposed surface of said wafer with ultraviolet (UV) light.
Claim 31
Dependent Claim
23 words
The method according to claim 25, wherein said step of electrochemically etching includes applying an anodic potential to said wafer in said cell.
Claim 32
Dependent Claim
13 words
The method according to claim 27, wherein said potential is between 0-3 volts.
Claim 33
Dependent Claim
27 words
The method according to claim 25, further including oxidizing porous portions of said wafer after said etching step to convert said porous silicon carbide into silicon dioxide.
Claim 34
Dependent Claim
14 words
The method according to claim 29, further including densifying the regions of silicon dioxide.
Claim 35
Dependent Claim
17 words
The method according to claim 30, wherein said densifying step comprises annealing said regions of silicon dioxide.
Claim 36
Dependent Claim
20 words
The method according to claim 25, wherein a monocrystalline layer of porous silicon carbid, is formed during said etching step.
Claim 37
Dependent Claim
17 words
The method according to claim 25, further including the step of passivating a surface of said layer.
Claim 38
Dependent Claim
24 words
The method according to claim 33, wherein said passivating step comprises forming a thin insulating layer on the surface of the said porous layer.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-10-02 | 1999-04-03 | 1999-10-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-10-02 | 2003-04-03 | 2003-10-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-10-02 | 2007-04-03 | 2007-10-03 | $7700.00 | Window Closed / Lapsed |