COMBINATION OF HALF-TONE MASK AND PUPIL FILTER FOR DEEP-UV (193-NM) LITHOGRAPHY

Abstract

We have investigated the aerial image characteristics for combinations of halftone mask (attenuated mask) and annular shaped pupil filter in the projection lens with deep ultraviolet (lambda=193 nm) source by computer simulation. The transmittance of halftone mask and the distribution of phase in the pupil are the main factors to be controlled for better image characteristics. Several combinations of halftone mask and pupil filter are investigated for each typical mask pattern such as equal line/space, isolated line, isolated space, and contact hole. The phase filter combined with 5% transmittance halftone mask gives larger depth of focus (DOF) for 0.2 mu m equal line/space pattern compared with that of the normal mask and pupil. This combination also shows better image profile with much larger DOF for 0.2 mu m contact hole pattern.