Transparent phase-shifting mask with multistage phase shifter and comb-shaped shifter

Abstract
This paper introduces the novel concepts of 'multistage phase shifter' and 'comb-shaped shifter' for resolving the problems of a transparent type phase shifting mask. The use of a multistage shifter decreases the light intensity dip at the shifter edges. The use of the comb- shaped shifter enables control of the pattern width. The effectiveness of a multistage shifter and a comb-shaped shifter were demonstrated by experiments and simulations. These technologies make it possible to fabricate a wide range of patterns for VLSI using the transparent phase shifting mask.