Patent US2257285A successfully refreshed from Google Patents.
US4599790A
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Process for forming a T-shaped gate structure
Assignee: Texas Instruments Inc
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Filing: 1985-01-30
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Granted: 1986-07-15
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Expires: 2005-01-30
Abstract
Abstract Using the present invention, a gate for a MESFET may be fabricated having a minimum gate length while having a low resistance gate. In addition, the present invention provides a method for forming a gate and gate recess which are perfectly aligned which is the optimal structure for high frequency power MESFETs. A two layer masking layer is fabricated having a first layer which may be etched uniformly and a second layer of lithographic material which may be photolithographic material such as AZ resist. A gate opening is patterned in the photoresist material and a metal such as gold is deposited by evaporation from acute angles on opposite sides of the gate opening in the resist. The deposited metal serves as a mask which covers all but a very small portion of the opening in the photoresist. The silicon nitride layer is then etched to form a gate opening and gate recess. Gate contact metal is then deposited in the opening thus formed and the nitride, photoresist and gold layers are removed, lifting off a portion of the gate metal layer thus leaving a T-shaped gate which provides a minimum length at the channel gate interface and provides a low gate resistance.
Inventors
- 👤 Bumman Kim
- 👤 Paul Saunier
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 15:29
CPC Classifications
H; H10; H10D; H10D30/00; H10D30/01; H10D30/061; H10D30/0612; H10D30/0614; H10D64/00; H10D64/01; H10D64/012; H10D64/0124; H10D64/0125; H10P; H10P76/00; H10P76/20; H10P76/202; Y; Y10; Y10S; Y10S148/00; Y10S148/143; Y10S438/00; Y10S438/942; Y10S438/948; Y10S438/951
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
166 words
A process for forming a T-shaped gate structure, comprising the steps of: providing a substrate; forming a first masking layer on the surface of said substrate; forming a second masking layer on the surface of said first masking layer; patterning said second masking layer; depositing a masking material on the surface of said first and second masking layers from a deposition source at an acute angle relative to the surface of said first and second masking layers thereby depositing a third masking layer on the surface of said first and second masking layers having an opening much smaller than and within the opening provided by said patterned second masking layer; etching the portion of said first masking layer exposed by said smaller opening in said third masking layer to said substrate; depositing gate material on the surfaces of said substrate and said first, second and third masking layers; removing said first, second and third masking layers thereby lifting off a portion of said deposited gate material.
Claim 2
Dependent Claim
166 words
A process for forming a T-shaped gate structure, comprising the steps of: providing a substrate; forming a first masking layer on the surface of said substrate; forming a second masking layer on the surface of said first masking layer; patterning said second masking layer; depositing a masking material on the surface of said first and second masking layers from a deposition source at an acute angle relative to the surface of said first and second masking layers thereby depositing a third masking layer on the surface of said first and second masking layers having an opening much smaller than and within the opening provided by said patterned second masking layer; etching the portion of said first masking layer exposed by said smaller opening in said third masking layer to said substrate; depositing gate material on the surfaces of said substrate and said first, second and third masking layers; removing said first, second and third masking layers thereby lifting off a portion of said deposited gate material.
Claim 3
Dependent Claim
15 words
A process as in claim 1 wherein said substrate is formed of crystalline gallium arsenide.
Claim 4
Dependent Claim
18 words
A process as in claim 1, further comprising the step of etching a gate recess in said substrate.
Claim 5
Dependent Claim
156 words
A process for forming a T-shaped gate structure, comprising the steps of: providing a substrate; forming a silicon nitride layer on the surface of said substrate; forming and patterning a resist layer on the surface of said silicon nitride layer; depositing metal material on the surface of said silicon nitride and resist masking layers from a deposition source at an angle relative to the surface of said substrate thereby depositing a metal masking layer on the surface of said silicon nitride and resist layers having an opening much smaller than and within the opening provided by said patterned resist layer; etching the portion of said silicon nitride layer exposed by said smaller opening in said metal masking layer to said substrate; depositing gate metal on the surfaces of said substrate and said silicon nitride, resist and metal layers; removing said silicon nitride, resist and metal layers thereby lifting off a portion of said deposited gate metal.
Claim 6
Dependent Claim
156 words
A process for forming a T-shaped gate structure, comprising the steps of: providing a substrate; forming a silicon nitride layer on the surface of said substrate; forming and patterning a resist layer on the surface of said silicon nitride layer; depositing metal material on the surface of said silicon nitride and resist masking layers from a deposition source at an angle relative to the surface of said substrate thereby depositing a metal masking layer on the surface of said silicon nitride and resist layers having an opening much smaller than and within the opening provided by said patterned resist layer; etching the portion of said silicon nitride layer exposed by said smaller opening in said metal masking layer to said substrate; depositing gate metal on the surfaces of said substrate and said silicon nitride, resist and metal layers; removing said silicon nitride, resist and metal layers thereby lifting off a portion of said deposited gate metal.
Claim 7
Dependent Claim
15 words
A process as in claim 4 wherein said substrate is formed of crystalline gallium arsenide.
Claim 8
Dependent Claim
11 words
A process as in claim 4 wherein said resist is photoresist.
Claim 9
Dependent Claim
18 words
A process as in claim 4, further comprising the step of etching a gate recess in said substrate.
Claim 10
Dependent Claim
195 words
A process for forming a metal semiconductor field effect transistor having a T-shaped gate structure, comprising the steps of: providing a substrate; forming source and drain areas in said substrate; forming a first masking layer on the surface of said substrate; forming a second masking layer on the surface of said first masking layer; patterning said second masking layer to provide a gate opening pattern above the region between said source and drain; depositing a masking material on the surface of said first and second masking layers from a deposition source at an acute angle relative to the surface of said first and second masking layers thereby depositing a third masking layer on the surface of said first and second masking layers having an opening much smaller than and within the opening provided by said patterned second masking layer; etching the portion of said first masking layer exposed by said smaller opening in said third masking layer to said substrate; depositing gate material on the surfaces of said substrate and said first, second and third masking layers; removing said first, second and third masking layers thereby lifting off a portion of said deposited gate material.
Claim 11
Dependent Claim
195 words
A process for forming a metal semiconductor field effect transistor having a T-shaped gate structure, comprising the steps of: providing a substrate; forming source and drain areas in said substrate; forming a first masking layer on the surface of said substrate; forming a second masking layer on the surface of said first masking layer; patterning said second masking layer to provide a gate opening pattern above the region between said source and drain; depositing a masking material on the surface of said first and second masking layers from a deposition source at an acute angle relative to the surface of said first and second masking layers thereby depositing a third masking layer on the surface of said first and second masking layers having an opening much smaller than and within the opening provided by said patterned second masking layer; etching the portion of said first masking layer exposed by said smaller opening in said third masking layer to said substrate; depositing gate material on the surfaces of said substrate and said first, second and third masking layers; removing said first, second and third masking layers thereby lifting off a portion of said deposited gate material.
Claim 12
Dependent Claim
26 words
A process as in claim 8 wherein said substrate has a conductivity type of P and said source and drain have a conductivity type of N.
Claim 13
Dependent Claim
16 words
A process as in claim 8 wherein said first masking layer is a silicon nitride layer.
Claim 14
Dependent Claim
15 words
A process as in claim 8 second masking layer is a layer of resist material.
Claim 15
Dependent Claim
12 words
A process as in claim 8 wherein said masking material is gold.
Claim 16
Dependent Claim
14 words
A process as in claim 8 wherein said masking material is deposited by evaporation.
Claim 17
Dependent Claim
18 words
A process as in claim 8, further comprising the step of etching a gate recess in said substrate.
Claim 18
Dependent Claim
210 words
A process for forming a metal semiconductor field effect transistor having a T-shaped gate structure, comprising the steps of: providing a substrate; forming a first masking layer on the surface of said substrate; forming a second masking layer on the surface of said first masking layer; patterning said second masking layer to provide a gate opening pattern above the region between said source and drain; depositing a masking material on the surface of said first and second masking layers from a deposition source at an acute angle relative to the surface of said first and second masking layers thereby depositing a third masking layer on the surface of said first and second masking layers having an opening much smaller than and within the opening provided by said patterned second masking layer; etching the portion of said first masking layer exposed by said smaller opening in said third masking layer to said substrate; depositing gate material on the surfaces of said substrate and said first, second and third masking layers; removing said first, second and third masking layers thereby lifting off a portion of said deposited gate material; forming source and drain regions on opposite sides of the remaining portion of said deposited gate material on the surface of said substrate.
Claim 19
Dependent Claim
210 words
A process for forming a metal semiconductor field effect transistor having a T-shaped gate structure, comprising the steps of: providing a substrate; forming a first masking layer on the surface of said substrate; forming a second masking layer on the surface of said first masking layer; patterning said second masking layer to provide a gate opening pattern above the region between said source and drain; depositing a masking material on the surface of said first and second masking layers from a deposition source at an acute angle relative to the surface of said first and second masking layers thereby depositing a third masking layer on the surface of said first and second masking layers having an opening much smaller than and within the opening provided by said patterned second masking layer; etching the portion of said first masking layer exposed by said smaller opening in said third masking layer to said substrate; depositing gate material on the surfaces of said substrate and said first, second and third masking layers; removing said first, second and third masking layers thereby lifting off a portion of said deposited gate material; forming source and drain regions on opposite sides of the remaining portion of said deposited gate material on the surface of said substrate.
Claim 20
Dependent Claim
26 words
A process as in claim 15 wherein said substrate has a conductivity type of P and said source and drain have a conductivity type of N.
Claim 21
Dependent Claim
16 words
A process as in claim 15 wherein said first masking layer is a silicon nitride layer.
Claim 22
Dependent Claim
15 words
A process as in claim 15 second masking layer is a layer of resist material.
Claim 23
Dependent Claim
12 words
A process as in claim 15 wherein said masking material is gold.
Claim 24
Dependent Claim
14 words
A process as in claim 15 wherein said masking material is deposited by evaporation.
Claim 25
Dependent Claim
18 words
A process as in claim 15, further comprising the step of etching a gate recess in said substrate.
References Cited (Backward Citations)
US4536942A
Cited
US4551905A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-07-14 | 1990-01-13 | 1990-07-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-07-14 | 1994-01-13 | 1994-07-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-07-14 | 1998-01-13 | 1998-07-15 | $7700.00 | Window Closed / Lapsed |