Patent US5529862A successfully refreshed from Google Patents.
US5529862A
Expired / Lapsed
US
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Method of forming a low distortion stencil mask
Assignee: Texas Instruments Inc
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Filing: 1993-09-01
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Granted: 1996-06-25
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Expires: 2013-09-01
Abstract
Abstract A stencil mask (10) has a membrane (14) under tensile stress and at least one pattern opening (22) formed through the membrane (14). A plurality of stress relief openings (30) are formed in the membrane for reducing stress-induced distortion of the membrane and the mask pattern. The stress relief openings (30) are positioned to relieve concentrations of stress within the membrane (14) such as those resulting from non-regularities within the pattern. In one embodiment, a screening material (56), less rigid than the membrane (14), is contained within the stress relief openings (30). Methods of forming such masks (10) are also disclosed.
Inventors
- 👤 John N. Randall
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 14:12
CPC Classifications
G; G03; G03F; G03F1/00; G03F1/20
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
127 words
A method for forming a stencil mask adapted for selectively passing radiation in a lithographic process, the method of forming the mask comprising the steps of: supporting a flexible membrane under sufficient tensional stress to maintain it in a substantially planar configuration, the membrane having a lithographic mask pattern comprising a plurality of pattern openings formed through the membrane; distributing tensional stress evenly throughout the membrane by forming a plurality of stress relief openings within the membrane, said stress relief openings being noncontiguous with said pattern openings; and blocking passage of the radiation through the stress relief openings by providing in said openings a flexible screening material which is softer and more flexible then the membrane and is positioned in alignment with the respective stress relief openings.
Claim 2
Independent Claim
127 words
A method for forming a stencil mask adapted for selectively passing radiation in a lithographic process, the method of forming the mask comprising the steps of: supporting a flexible membrane under sufficient tensional stress to maintain it in a substantially planar configuration, the membrane having a lithographic mask pattern comprising a plurality of pattern openings formed through the membrane; distributing tensional stress evenly throughout the membrane by forming a plurality of stress relief openings within the membrane, said stress relief openings being noncontiguous with said pattern openings; and blocking passage of the radiation through the stress relief openings by providing in said openings a flexible screening material which is softer and more flexible then the membrane and is positioned in alignment with the respective stress relief openings.
Claim 3
Dependent Claim
84 words
The method of claim 1, wherein the step of distributing tensional stress evenly throughout the membrane comprises: defining a plurality of membrane subfields; determining the total area within each subfield occupied by any pattern openings and determining the densities of pattern area in the respective subfields; forming a relatively high concentration of stress relief openings in subfields having lower than average densities of pattern area and a relatively low concentration of stress relief openings in subfields having higher than average densities of pattern area.
Claim 4
Dependent Claim
48 words
The method of claim 2, wherein the step of relieving tensional stress within the membrane comprises forming sufficiently high densities of stress relief openings in subfields having lower than average densities of pattern area to substantially equalize the density of pattern and stress relief openings throughout the membrane.
References Cited (Backward Citations)
US3742230A
Cited
US4342817A
Cited
US4468799A
Cited
US4647517A
Cited
US4708919A
Cited
US4780382A
Cited
US4855197A
Cited
US4827138A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-06-25 | 1999-12-25 | 2000-06-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-06-25 | 2003-12-25 | 2004-06-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-06-25 | 2007-12-25 | 2008-06-25 | $7700.00 | Window Closed / Lapsed |