Application of atomic-force microscopy to phase-shift masks

Abstract

In recent years, optical phase shifting masks (PSM) have become of interest for the enhancement of submicron lithographic techniques. Various schemes of PSMs have been published in the literature demonstrating improvement in performance of optical lithography techniques for 0.5 μm features and below. Some of these schemes require features on the PSMs that are micron or submicron in size. Monitoring the depth as well as the lateral dimensions of these small features is important in order to meet the dimensional tolerances. In this paper we report the application of an atomic force microscope (AFM) to obtain both quantitative as well as qualitative information about the etched features in a PSM.