US4687682A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Back sealing of silicon wafers
Assignee: AT&T Inc
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Filing: 1986-05-02
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Granted: 1987-08-18
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Expires: 2006-05-02
Abstract
Abstract Sealing the backside of a semiconductor wafer prevents evaporation of the dopant (typically boron) when an epitaxial layer is grown on the front (active) side, thereby preventing autodoping of the epitaxial layer with excess dopant. The present technique deposits an oxide layer during the ramp-up of the furnace that also deposits the nitride cap, thereby avoiding an extra process step. It also avoids the higher temperatures required for the prior-art technique of growing the oxide layer, resulting in lower oxygen precipitation due to the capping process and a greater yield of usable wafers.
Inventors
- 👤 Jeffrey T. Koze
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 12:08
CPC Classifications
H; H10; H10P; H10P14/00; H10P14/60; H10P14/66; H10P14/668; H10P14/6681; H10P14/6684; H10P14/6686; H10P14/63; H10P14/6326; H10P14/6328; H10P14/6334; H10P14/662; H10P14/6682; H10P14/69; H10P14/692; H10P14/6921; H10P14/69215; H10P14/694; H10P14/6943; H10P14/69433; H10P32/00; H10P32/10; H10P32/15; H10P36/00; H10P36/20; Y; Y10; Y10S; Y10S148/00; Y10S148/007; Y10S148/015; Y10S148/06; Y10S438/00; Y10S438/914; Y10S438/916
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
124 words
A method of making a solid state device by steps comprising capping a back side of a semiconductor wafer in preparation for forming an epitaxial layer of a semiconductor material on the front side of said wafer, characterized in that said capping is accomplished by steps comprising: introducing said wafer into a furnace; increasing the temperature in said furnace while introducing a source gas comprising a silicon compound and a source of oxygen into said furnace, thereby depositing silicon dioxide onto said wafer during said increasing the temperature; maintaining said furnace at an elevated temperature and introducing a source of silicon and a source of nitrogen into said furnace, thereby depositing silicon nitride onto said silicon dioxide; and removing said wafer from said furnace.
Claim 2
Independent Claim
124 words
A method of making a solid state device by steps comprising capping a back side of a semiconductor wafer in preparation for forming an epitaxial layer of a semiconductor material on the front side of said wafer, characterized in that said capping is accomplished by steps comprising: introducing said wafer into a furnace; increasing the temperature in said furnace while introducing a source gas comprising a silicon compound and a source of oxygen into said furnace, thereby depositing silicon dioxide onto said wafer during said increasing the temperature; maintaining said furnace at an elevated temperature and introducing a source of silicon and a source of nitrogen into said furnace, thereby depositing silicon nitride onto said silicon dioxide; and removing said wafer from said furnace.
Claim 3
Dependent Claim
20 words
The method of claim 1 wherein said source gas comprising a silicon compound and said source of oxygen is tetraethylorthosilicate.
Claim 4
Dependent Claim
15 words
The method of claim 1 wherein said source gas comprising a silicon compound is dichlorosilane.
Claim 5
Dependent Claim
12 words
The method of claim 1 wherein said source of nitrogen is ammonia.
Claim 6
Dependent Claim
20 words
The method of claim 1 wherein said depositing silicon dioxide is substantially accomplished at a temperature below 775 degrees C.
Claim 7
Dependent Claim
21 words
The method of claim 1 wherein said depositing silicon dioxide is accomplished during a time period of less than 10 minutes.
Claim 8
Dependent Claim
33 words
The method of claim 1 further comprising the step of polishing the front side of said wafer following said removing said wafer from said furnace and prior to said forming an epitaxial layer.
Claim 9
Dependent Claim
14 words
The method of claim 7 wherein said polishing is accomplished with a caustic slurry.
Claim 10
Dependent Claim
26 words
The method of claim 1 wherein said wafer as introduced into said furnace has a concentration of unprecipitated oxygen of at least 10 parts per million.
Claim 11
Dependent Claim
22 words
The method of claim 9 wherein the concentration of unprecipitated oxygen in said wafer is substantially unchanged during said depositing silicon dioxide.
Claim 12
Dependent Claim
26 words
The method of claim 1 wherein said wafer as introduced into said furnace has a doping level of at least 10 18 atoms per cubic centimeter.
Claim 13
Dependent Claim
15 words
The method of claim 11 wherein the dopant that produces said doping level is boron.
Claim 14
Dependent Claim
33 words
The method of claim 1 further comprising the step of precipitating a substantial amount of unprecipitated oxygen in said wafer so as to getter impurities following said removing said wafer from said furnace.
Claim 15
Dependent Claim
13 words
The method of claim 1 wherein said semiconductor wafer is a silicon wafer.
References Cited (Backward Citations)
US3556841A
Cited
US3663319A
Cited
US3660180A
Cited
US3769104A
Cited
US3716422A
Cited
US3669769A
Cited
US3765960A
Cited
US3934060A
Cited
US4438157A
Cited
JPS60211846A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-08-17 | 1991-02-16 | 1991-08-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-08-17 | 1995-02-16 | 1995-08-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-08-17 | 1999-02-16 | 1999-08-18 | $7700.00 | Window Closed / Lapsed |