Device photolithography: The primary pattern generator part i-optical design

I. INTRODUCTION The basic design concept of the primary pattern generator (PPG) is the production of a linearly scanning, small, constant-size light spot. The scanning system consists of a regular polygonal-prism mirror which rotates about its axis of highest symmetry. The mirror faces are used sequentially to reflect a collimated light beam into a lens (for example, the scanning lens of Fig. 1). The collimated light is focused to a spot which scans a line in the focal plane of the lens as the polygonal mirror rotates. Located in the focal plane of the lens is a flat, glass photographic plate. The glass plate is moved by the desired scan line separation during the time required to bring the succeeding mirror facet into proper position.