Patent US4147584A successfully refreshed from Google Patents.
US4147584A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for providing low cost wafers for use as substrates for integrated circuits
Assignee: Unisys Corp
•
Filing: 1977-12-27
•
Granted: 1979-04-03
•
Expires: 1997-12-27
Abstract
Abstract The method of manufacture of the present invention provides a wafer that is better than a bulk monocrystalline silicon wafer and equivalent to silicon on sapphire (SOS) wafers for use as substrates for integrated circuits. The method comprises taking an inexpensive slab of silicon having <111> crystal orientation and by low pressure CVD, high pressure CVD, or plasma deposition techniques depositing a polycrystalline layer of sapphire on the <111> silicon base. The polycrystalline layer of sapphire is then annealed at an elevated temperature to form a monocrystalline layer having a <1101> orientation. A single crystalline layer of silicon having <111> crystal orientation is then epitaxially grown on the sapphire. The resultant multilayer wafer is equivalent in function and reliability to a silicon on sapphire wafer without the commensurate cost.
Inventors
- 👤 Lilburn H. Garrison
- 👤 Anant D. Dixit
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 12:43
CPC Classifications
H; H10; H10P; H10P14/00; H10P14/60; H10P14/69; H10P14/692; H10P14/6938; H10P14/6939; H10P14/69391; H10P14/20; H10P14/24; H10P14/29; H10P14/2901; H10P14/2902; H10P14/2905; H10P14/2926; H10P14/32; H10P14/3202; H10P14/3238; H10P14/3258; H10P14/34; H10P14/3402; H10P14/3404; H10P14/3411; H10P14/3466; H10P14/63; H10P14/6326; H10P14/6328; H10P14/6334; H10P14/65; H10P14/6516; H10P14/6544; Y; Y10; Y10S; Y10S117/00; Y10S117/901; Y10S117/902; Y10S148/00; Y10S148/072; Y10S148/135; Y10S438/00; Y10S438/967
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
84 words
A method for manufacturing wafers for use as substrates for integrated circuits, which wafers have a minimum of crystal defects, said method comprising: depositing a polycrystalline layer of pure sapphire upon a crystalline body having <111> orientation; annealing the polycrystalline layer of pure sapphire sufficiently to form a monocrystalline layer of pure sapphire, said monocrystalline sapphire layer having <1101> orientation; and depositing an epitactic monocrystalline layer of silicon upon the layer of monocrystalline pure sapphire, said epitactic monocrystalline silicon layer having a <111> orientation.
Claim 2
Independent Claim
84 words
A method for manufacturing wafers for use as substrates for integrated circuits, which wafers have a minimum of crystal defects, said method comprising: depositing a polycrystalline layer of pure sapphire upon a crystalline body having <111> orientation; annealing the polycrystalline layer of pure sapphire sufficiently to form a monocrystalline layer of pure sapphire, said monocrystalline sapphire layer having <1101> orientation; and depositing an epitactic monocrystalline layer of silicon upon the layer of monocrystalline pure sapphire, said epitactic monocrystalline silicon layer having a <111> orientation.
Claim 3
Dependent Claim
18 words
The method of claim 1 wherein the layer of sapphire is deposited to a thickness of 1 micron.
Claim 4
Dependent Claim
24 words
The method of claim 2 wherein the layer of silicon deposited on the layer of sapphire is deposited to a thickness of 2 microns.
Claim 5
Dependent Claim
28 words
The method of claim 1 wherein the step of depositing sapphire upon a crystalline body having <111> orientation is accomplished by using a CVD high gas flow reactor.
Claim 6
Dependent Claim
25 words
The method of claim 1 wherein the step of depositing sapphire upon a crystalline body having <111> orientation is accomplished by using a plasma reactor.
Claim 7
Dependent Claim
26 words
The method of claim 1 wherein the step of depositing sapphire upon a crystalline body having <111> orientation is accomplished by using a low pressure reactor.
Claim 8
Dependent Claim
165 words
The method of claim 1 wherein the step of depositing sapphire upon a crystalline body having <111> orientation, comprises: placing the <111> crystalline body in a controlled atmosphere environment having a pressure range of 0.5-0.9 torr; heating the <111> crystalline body within said controlled environment to a temperature within the range 250°-350° C., inclusive; flowing an inert carrier gas, such as hydrogen, through said controlled environment at a rate of approximately 600 cc/min.; and flowing trimethyl aluminum through said controlled environment at a rate within the range 40-80 cc/min., inclusive, and wherein the step of annealing comprises: placing the <111> crystalline body with the polycrystalline layer of sapphire deposited therein in a controlled atmosphere environment of inert gas, such as nitrogen; heating the environment to a temperature within the range 1100°-1300° C., inclusive; and leaving the <111> crystalline body with the polycrystalline layer of sapphire therein in the heated environment from 4 to 8 hours, until the polycrystalline layer is converted to a monocrystalline 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) | 1982-04-02 | 1982-10-02 | 1983-04-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-04-02 | 1986-10-02 | 1987-04-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-04-02 | 1990-10-02 | 1991-04-03 | $7700.00 | Window Closed / Lapsed |