High na duv printing tool with combination of oblique illumination source for 0.25 .MU.m lithography application.

Abstract

In this paper, the performance of quadrapole illumination source under two types of high numerical aperture (NA) deep-ultra-violet (DUV) printing tools, namely, excimer laser stepper with chromatic lens design and step-and-scan systems without chromatic aberration for the application of 0.25μm lithography is studied through simulation. The results are based on both aerial image and Shipley XP89131 negative DUV resist model [1] study. Due to the unique characteristics of oblique illumination source imaging, i.e., imaging by using only zero and first diffraction order light, both stepper resolution limit and depth of focus (DOF) of dense lines are extended. As a result, the proximity effect and the chromatic aberration effect in resist printing are also different from that of conventional illumination source. The optical proximity effect increases under the oblique illumination source as compared to that of conventional illumination source, especially when the light incident angle is large. For chromatic lens aberration, unlike the conventional illumination source, aerial image degradation depends not only on the laser spectral profile and amount of the lens aberration, but also on the mask feature sizes and pattern types.