157 nm lithography with high numerical aperture lens for the 70 nm technology node

Abstract

157 nm lithography is being investigated for the sub-70 nm technology node of semiconductor devices. Many efforts have been reported on the exposure tool, the F2 laser, the resist materials, the resist processing and the mask materials. A critical component for the success of this 157 nm lithography is the availability of high numerical aperture (NA) lenses that lead to higher resolution capability and higher process margin. In this paper, we describe our recent evaluation results of a high precision 157 nm Microstepper with 0.85 NA lens combined with simulation analysis of the lithographic performance. The details of the evaluation results discussed here include the resolution limit of the high NA lens and the possible effects of intrinsic birefringence upon the lithographic performance.