Method of fabrication of photomasks
Abstract
Abstract A PHOTOMASK HAS MULTILAYER OPAQUE PLATTERNS ON A TRANSPARENT SUBSTRATE. EACH PATTERN INCLUDES A BOTTOM LAYER AND A TOP LAYER, EACH OF A MATERIAL CAPABLE OF BEING ETCHED BY A SUBSTANCE WHICH WILL NOT ETCH THE SUBSTRATE, AND AN INTERMEDIATE LAYER OF A MATERIAL CAPABLE OF BEING ETCHED BY A SUBSTANCE WHICH WILL NOT ETCH THE BOTTOM AND TOP LAYERS. THE SEVERAL LAYERS COMPENSATE FOR DEFECTS IN EACH LAYER. AN IMPROVED PHOTOMASK FABRICATION METHOD INCLUDES FORMING THE ABOVEMENTIONED PATTERNS BY SUCCESSIVELY DEPOSITING THE BOTTOM AND INTERMEDIATE LAYERS, PHOTOETCHING THE INTERMEDIATE LAYER INTO A DESIRED PATTERN, DEPOSITING THE TOP LAYER, AND THEN PHOTOETCHING THE TOP AND BOTTOM LAYERS INTO A DESIRED PATTERN.
Inventors
- 👤 Andrew G F Dingwall
Bibliographic Details
Claims Analysis
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-06-27 | 1975-12-27 | 1976-06-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-06-27 | 1979-12-27 | 1980-06-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-06-27 | 1983-12-27 | 1984-06-27 | $7700.00 | Window Closed / Lapsed |