Measurement of residual birefringence in photomask blanks

Abstract

Residual linear birefringence is an important property for quality control of optical components used in optical lithographic instruments. We present in this paper a sensitive instrument to measure both the magnitude and angular orientation of residual linear birefringence in optical components, including photomask blanks. A variety of optical components are studied using this instrument. We will focus on the birefringence measurement of photomask blanks in this report. We have identified different patterns and levels of residual linear birefringence in these samples. We hope that the data provided in this paper will be helpful to the suppliers of photomask blanks, photomask manufacturers, and producers of optical microlithography instruments.