Device Photolithography: The Primary Pattern Generator: Part IV: Alignment and Performance Evaluation

The Primary Pattern Generator Part IV-Alignment and Performance Evaluation By A. M. J O H N S O N and A. ZACHARIAS (Manuscript received July 10, 1970) T h e mechanical n a t u r e o f t h e p r i m a r y p a t t e r n generator ( P P G ) requires a precise juxtaposition of most of t h e m a c h i n e elements in order to achieve both p a t t e r n accuracy a n d reliable f u n c t i o n i n g of t h e machine. P a r t II described the a l i g n m e n t of t h e r o t a t i n g polygonal mirror to t h e air-bearing axis. T h e precision required in t h a t assembly is t h e tightest tolerance in t h e P P G . T h i s precision is required to p r o duce a u n i f o r m scan-line spacing on the p a t t e r n . In addition, t h e direction of t h a t scan line m u s t be m a d e as p e r p e n d i c u l a r as possible to t h e t r a v e l direction of the photographic plate. T h e r e f o r e , t h e carriage of t h e p h o t o g r a p h i c p l a t e m u s t move w i t h o u t r o t a t i o n . T h e method for aligning t h e polygonal mirror axis to t h e carriage direction will be described, as well as other alignment needed to produce an a c c u r a t e p a t t e r n . T h e code-plate s y s t e m for controlling t h e fast scan was described in P a r t s I a n d I I I . Implicit in this description was t h e a s s u m p tion t h a t t h e code-plate grating and the p h o t o g r a p h i c p l a t e are t h e exact same distance f r o m t h e scanning lens (see Fig. 1 in Ref 1).