US4351892A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Alignment target for electron-beam write system
Assignee: National Semiconductor Corp
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Filing: 1981-05-04
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Granted: 1982-09-28
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Expires: 2001-05-04
Abstract
Abstract An alignment target for an electron-beam direct write system is formed on a wafer of semiconductor material. First, a layer of silicon oxide is formed on a surface of the wafer. Then a layer of silicon nitride is formed on the oxide. Next, an opening is etched in the nitride layer to expose a surface portion of the oxide. The surface portion of the oxide is then etched to form a hole in the oxide. The hole is formed such that the oxide layer is undercut beneath the nitride layer such that a cantilevered nitride overhang is formed around the perimeter of the hole. A layer of aluminum is then deposited over the nitride layer.
Inventors
- 👤 T. Grant Davis
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 03:53
CPC Classifications
H; H10; H10W; H10W46/00; G; G03; G03F; G03F9/00; H10W46/501; Y; Y10; Y10S; Y10S438/00; Y10S438/975
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
153 words
A method for aligning an electron beam of an electron-beam direct write system with a wafer of semiconductor material, comprising: (a) forming an alignment target on the wafer by the steps of (i) forming a layer of silicon oxide on a surface of said wafer; (ii) forming a layer of silicon nitride on said oxide layer; (iii) etching an opening in said nitride layer to expose a surface portion of said oxide layer; (iv) etching said exposed surface portion to form a hole in said oxide layer, said hole being formed such that said oxide layer is undercut beneath said silicon nitride layer such that a cantilevered silicon nitride overhang is formed around the perimeter of said hole; and (v) depositing a layer of aluminum over said nitride layer; (b) scanning the surface of the wafer with the electron beam; and (c) detecting the alignment of the electron beam with the alignment target.
Claim 2
Independent Claim
153 words
A method for aligning an electron beam of an electron-beam direct write system with a wafer of semiconductor material, comprising: (a) forming an alignment target on the wafer by the steps of (i) forming a layer of silicon oxide on a surface of said wafer; (ii) forming a layer of silicon nitride on said oxide layer; (iii) etching an opening in said nitride layer to expose a surface portion of said oxide layer; (iv) etching said exposed surface portion to form a hole in said oxide layer, said hole being formed such that said oxide layer is undercut beneath said silicon nitride layer such that a cantilevered silicon nitride overhang is formed around the perimeter of said hole; and (v) depositing a layer of aluminum over said nitride layer; (b) scanning the surface of the wafer with the electron beam; and (c) detecting the alignment of the electron beam with the alignment target.
Claim 3
Dependent Claim
35 words
The method of claim 1 wherein said aluminum layer is deposited over said nitride layer and in said hole such that a continuous gap exists between said nitride overhang and said aluminum in said hole.
Claim 4
Dependent Claim
13 words
The method of claim 1 wherein said hole is rectangular in horizontal cross-section.
Claim 5
Dependent Claim
13 words
The method of claim 1 wherein said hole is square in horizontal cross-section.
Claim 6
Dependent Claim
15 words
The method of claim 1 wherein said hole extends to the surface of said wafer.
Claim 7
Dependent Claim
15 words
The method of claim 1 wherein said silicon oxide layer is about 1.45 microns thick.
Claim 8
Dependent Claim
15 words
The method of claim 6 wherein said silicon nitride layer is about 700 Angstroms thick.
Claim 9
Dependent Claim
14 words
The method of claim 7 wherein said nitride overhang is about 2 microns wide.
Claim 10
Dependent Claim
14 words
The method of claim 8 wherein said aluminum layer is about 0.70-1.0 microns thick.
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) | 1985-09-27 | 1986-03-29 | 1986-09-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-09-27 | 1990-03-29 | 1990-09-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-09-27 | 1994-03-29 | 1994-09-28 | $7700.00 | Window Closed / Lapsed |