PHOTOMASK SUBSTRATE, PHOTOMASK SUBSTRATE MOLDING MEMBER, PHOTOMASK SUBSTRATE MANUFACTURING METHOD, PHOTOMASK, AND EXPOSURE METHOD USING PHOTOMASK

摘要

A photomask substrate having a substantially uniform thickness, which includes a first surface on which a mask pattern is to be formed, and a second surface, which are continuous curved surfaces. The first surface has a quadrangular shape including a first set of opposing sides and a second set of opposing sides, and has a support portion at an end along each side of the first set. When the photomask substrate is held so that the first surface is substantially vertical, a reference plane parallel to the tangential plane of the first surface at the center point of the first surface is used as the photomask substrate. On the other hand, it is defined on the side closer to the first surface than the second surface. At this time, the first distance along the thickness direction between the center point of the first surface and the reference plane is along the thickness direction between the midpoint of each side of the second set and the reference plane. Shorter than the second distance.