Protective dust cover for photomask or reticle
US5100957A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 22, 1991 |
| Grant date | Mar 31, 1992 |
| Priority date | — |
| Expiry date | Jul 22, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03F1/62
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A protective dust cover for a photomask or reticle useful for forming semiconductor integrated circuits, which is a transparent thin film cover to be disposed with a certain distance from the substrate surface of the photomask or reticle for the protection and dust proof of the substrate surface, said transparent thin film consisting essentially of a polyvinyl acetal of the formula: ##STR1## wherein R is a hydrogen atom, --CH.sub.3, --C.sub.2 H.sub.5 or --C.sub.n H.sub.m F.sub.2n-m+1 wherein n is an integer of from 1 to 8 and m is an integer of from 0 to 2n, x is a number of from 5 to 40, y is a number of from 0 to 10, z1 is a number of from 0 to 90/2, and z2 is a number of from 3/2 to 95/2, having a vinyl acetate content of at most 10 mol % and an acetal content of at least 60 mol %.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.