Understanding EUV Shot Noise: Comparing Theory and Requirements to Experimental Evidence

Abstract

High resolution contact holes were printed with different EUV resists on an EUV microstepper exposure tool. Intrinsic critical dimension uniformity (corrected CDU) was separated statistically from other location effects. As expected, there was worse CDU for resists with lower dose to size. Comparison of corrected CDU to calculated shot noise showed a significant correlation. However the CDU of the fastest resists tested showed substantial variation, suggesting that different chemical approaches to making fast resists can give different CDU. Comparison of experimental results and of calculated shot noise to ITRS roadmap requirements for contact hole CDs suggests that some post processing that improves CDU will be needed in the future or that chip designs with tolerance to significant contact hole CDU will be needed.