FOCAL PLANE ADJUSTED PHOTOMASK AND METHODS OF PROJECTING IMAGES ONTO PHOTOSENSITIZED WORKPIECE SURFACES

摘要

In the operation of a projection printer (11) photomasks (22), the patterns (21) of which are protected by coverplates (39), are used interchangeably with other photomasks, the patterns of which are located at an open surface thereof. The photomasks (22) feature shims (46) which space the patterns (21) away from a plane of support surfaces (13) of a mounting chuck (12) by a precise distance equal to the shift of the object plane (14) with respect to an image plane (17) because of the presence of the coverplate (39) in the optical path of the projection printer (11).