The detectability of Qz phase defects and its application for 65nm node CPL mask manufacturing

Abstract

RET (Resolution Enhancement Technique) is strongly required for 65nm node pattern generation. Alternating Phase Shift Masks (APSM) and Chrome-less Phase Lithography (CPL) masks are widely used for the purpose of RET. However, APSM and CPL mask manufacturing is rather complex and difficult in terms of their structure and fabrication. To inspect these kind of RET masks is very difficult because of quartz (Qz) phase defects which can hardly be detected by using a conventional inspection method. Since Qz phase defect is the key issue in APSM or CPL mask manufacturing, many works have been done widely so far. Here we've evaluated the defocus inspection method to find best inspection condition for detecting Qz phase defects. We conclude that the best condition for finding Qz phase defects could have dependency upon the pattern shape and size. Moreover, the limitation of the inspection capability for Qz phase defect inspection has been addressed with comparison of the wafer print result.