Lens Aberration Effect on the Line Width for Different Pattern Shapes and Duty Ratios

Abstract

The most important issue in lithography as a semiconductor process is to obtain the minimum resolution. In order to obtain the minimum resolution with processible depth of focus, the numerical aperture of the scanner projection Ions is gradually increased, and the exposure wavelength is decreased. The effect of aberration is also increased as a result. Although aberration effects are not that important for critical dimensions (CD) greater than 300 nm, they must be considered for CDs smaller than 100 nm in order to obtain the best process condition. The purpose of this study is to evaluate the aberration effect of the projection system for a 90 nm semiconductor device. Our evaluation is done by comparing the various aberration effects for different exposure wavelengths, different shapes such as isolated, line and space, contact hole, and L-shaped patterns, and for different duty ratios by using the commercial lithography simulator Solid-C.