Simulation of coherent multiple imaging by means of pupil-plane filtering in optical microlithography

A resolution enhancement technique for optical microlithography based on co herent multiple imaging was investigated with use of Prolith/2 (a commercia l lithographic simulation tool). It was shown that a Fabry-Perot etalon pla ced between the mask and the projection lens of an optical stepper could be interpreted as an appropriate transmission-phase pupil-plane filter. While previous calculations were able to evaluate simple patterns (such as an on -axis contact hole), this new approach also allows the simulation of comple x mask patterns. Evaluation of the point-spread function of the optical sys tems by means of coherent multiple imaging showed that an optimized filter is capable of increasing the resolution by 28% and the depth of focus by 15 0%. (C) 1999 Optical Society of America [S0740-3232(99)00408-1].