Mask overlay checking means
Abstract
Abstract A METHOD FOR COMPARING THE PATTERN IN A PAIR OF LIGHT MASKS, E.G., MASKS HAVING REGIONS TRANSPARENT TO LIGHT AND REGIONS OPAQUE TO LIGHT. A LIGHT MASKING COPY, EITHER POSITIVE OR NEGATIVE, OF EACH OF THE MASKS IS MADE. THE OPAQUE REGION IN ONE OF SAID COPIES IS RENDERED SEMITRANSPARENT, AFTER WHICH A LIGHT SENSITIVE SUBSTRATE IS EXPOSED THROUGH BOTH OF SAID COPIES SUPERIMPOSED IN REGISTRATION WITH EACH OTHER TO PRODUCE A THREE-TONE COMPOSITE IMAGE IN THE LIGHT SENSITIVE SUBSTRATE OF THE PAIR OF MASKS IN REGISTRATION. WHERE ONE OF THE MASKS HAS SMALLER REGIONS WHICH SHOULD BE POSITIONED WITHIN LIMITS OF LARGER REGIONS ON THE OTHER MASK WHEN SAID MASKS ARE USED IN REGISTRATION WITH EACH OTHER, THE TYPE OF COPY, EITHER POSITIVE OR NEGATIVE, MADE OF EACH MASK AS WELL AS THE SELECTION OF THE MASK IN WHICH THE OPAQUE REGIONS ARE RENDERED SEMITRANSPARENT IS GOVERNED BY THE THE REQUIREMENT THAT SAID SMALLER REGIONS IN SAID COPIES ARE AT LEAST AS OPAQUE AS SAID LARGER REGIONS.
Inventors
- 👤 William O Druschel
Bibliographic Details
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