US4560435A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Composite back-etch/lift-off stencil for proximity effect minimization
Assignee: International Business Machines Corp
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Filing: 1984-10-01
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Granted: 1985-12-24
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Expires: 2004-10-01
Abstract
Abstract This composite back-etch/lift-off stencil method avoids the uncontrolled changes in the properties of contacts in small devices caused by the close proximity of the lift-off resist stencil to the contact area during the precleaning, surface preparation and metal deposition processes. This method limits the area of the wafer exposed to back-etching and thus restores the freedom of choice of contact metallurgy. Back-etching is only applied in the areas of the wafer near to the contact holes; lift-off techniques are used for the rest of the integrated circuit.
Inventors
- 👤 Karen H. Brown
- 👤 David F. Moore
- 👤 Bernard J. C. van der Hoeven, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 14:14
CPC Classifications
H; H10; H10N; H10N60/00; H10N60/01; H10N60/0912; H10P; H10P76/00; H10P76/20; H10P76/202; Y; Y10; Y10S; Y10S438/00; Y10S438/942; Y10S438/948; Y10S438/951; Y10S505/00; Y10S505/80; Y10S505/815; Y10S505/818; Y10S505/82
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
131 words
A method for making integrated circuits having critical wafer areas which are susceptible to proximity effect degradation at critical areas --characterized by-- (a) patterning a lift-off resist stencil factor with windows including contact dimensions and extension dimensions extending beyond the contact dimensions in the critical areas with respect to proximity effects; (b) depositing contact metal using the windows as a pattern, covering both contact dimensions and extension dimensions; (c) patterning a back-etch resist stencil factor over selected portions of said contact metal, providing protection to the underlying layers within the contact dimensions but exposing contact metal within the extension dimensions; (d) back etching to the selected pattern of metallization by removing contact metal from the extension dimensions; and (e) removing said lift-off resist stencil factor and said back-etch resist stencil factor.
Claim 2
Independent Claim
131 words
A method for making integrated circuits having critical wafer areas which are susceptible to proximity effect degradation at critical areas --characterized by-- (a) patterning a lift-off resist stencil factor with windows including contact dimensions and extension dimensions extending beyond the contact dimensions in the critical areas with respect to proximity effects; (b) depositing contact metal using the windows as a pattern, covering both contact dimensions and extension dimensions; (c) patterning a back-etch resist stencil factor over selected portions of said contact metal, providing protection to the underlying layers within the contact dimensions but exposing contact metal within the extension dimensions; (d) back etching to the selected pattern of metallization by removing contact metal from the extension dimensions; and (e) removing said lift-off resist stencil factor and said back-etch resist stencil factor.
Claim 3
Independent Claim
187 words
A method for making integrated circuits having critical wafer areas with respect to proximity effects, which areas require protection from process-related degradation --characterized by -- (a) patterning a lift-off resist stencil factor over the wafer omitting the critical areas with respect to proximity effects; (b) patterning a combination contact metal stencil factor generally coextensive to the critical areas, using the lift-off resist stencil factor as a pattern, providing coverage with contact metal material in the critical areas not only where desired as a contact metallization, but with excess coverage extending to the boundary of said lift-off resist stencil factor, whereby a composite contact metal/lift-off stencil is completed; (c) patterning a back-etch resist stencil over selected portions of said contact metal stencil factor extending less than the entire distance to said lift-off resist stencil factor, to define a desired metal contact configuration; (d) back-etching said contact metal stencil factor to the selected configuration of contact metal; and (e) removing the lift-off resist stencil factor; whereby the contact metal remains in the selected configuration and the critical area remains free of lift-off stencil factor and any resulting proximity effects.
Claim 4
Independent Claim
187 words
A method for making integrated circuits having critical wafer areas with respect to proximity effects, which areas require protection from process-related degradation --characterized by -- (a) patterning a lift-off resist stencil factor over the wafer omitting the critical areas with respect to proximity effects; (b) patterning a combination contact metal stencil factor generally coextensive to the critical areas, using the lift-off resist stencil factor as a pattern, providing coverage with contact metal material in the critical areas not only where desired as a contact metallization, but with excess coverage extending to the boundary of said lift-off resist stencil factor, whereby a composite contact metal/lift-off stencil is completed; (c) patterning a back-etch resist stencil over selected portions of said contact metal stencil factor extending less than the entire distance to said lift-off resist stencil factor, to define a desired metal contact configuration; (d) back-etching said contact metal stencil factor to the selected configuration of contact metal; and (e) removing the lift-off resist stencil factor; whereby the contact metal remains in the selected configuration and the critical area remains free of lift-off stencil factor and any resulting proximity effects.
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) | 1988-12-23 | 1989-06-24 | 1989-12-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-12-23 | 1993-06-24 | 1993-12-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-12-23 | 1997-06-24 | 1997-12-24 | $7700.00 | Window Closed / Lapsed |