Lithographic mask structure and device for positioning the same

Claim 1

A combination of a lithographic mask having a pattern formed on a membrane used for the manufacture of a semiconductor devices and a positioning device having a movable holder for holding and positioning the mask, the combination comprising: a generally ring-like frame member for supporting the membrane, said frame member having a substantially circumferentially extending peripheral surface portion and a substantially flat surface portion extending in a direction intersecting the membrane and providing a positional reference for the mask; a light source for projecting a light beam to said substantially flat surface portion of said frame member of the mask as held by the holder; a detector for detecting at least a portion of a light beam reflected by said flat surface portion of said frame member, said detector producing an output corresponding to the detected light beam; and control means for controlling at least one of a rotational position and a translational position of the holder in response to the output of said detector.