Pattern dependent alignment technique for mix-and-match electron-beam lithography with optical lithography

Abstract

An alignment technique for electron-beam (EB) lithography that corrects the writing pattern to match the pattern-dependent lens distortion of an optical stepper is proposed. In mix-and-match EB and optical lithography, precise measurement of positional distortion caused by the stepper lens is necessary. However, recent research in optical lithography has shown that the lens distortion differs depending on the pattern features. Thus, we have enhanced the measurement method to reflect the pattern-feature dependence of positional distortion in optical lithography. To measure the various types of distortions more effectively, we modified the marks used for distortion and overlay measurement. The measured pattern dependence of the lens distortion was in good agreement with our simulation results and the overlay accuracy in mix-and-match lithography was improved with this method.