Lithography hotspot discovery at 70nm DRAM 300mm fab: Process Window Qualification using Design Base Binning

Abstract

Identifying hotspots - structures that limit the lithography process window - become increasingly important as the industry relies heavily on RET to print subwavelength designs. KLA-Tencor's patented Process Window Qualification (PWQ) methodology has been used for this purpose in various fabs. PWQ methodology has three key advantages (a) PWQ Layout - to obtain the best sensitivity (b) Design Based Binning - for pattern repeater analysis (c) Intelligent sampling - for the best DOI sampling rate. This paper evaluates two different analysis stratagies for SEM review sampling successfully deployed at Inotera Memories, Inc. We propose a new approach combining the location repeater and pattern repeaters. Based on a recent case study the new sampling flow reduces the data analysis and sampling time from 6 hours to 1.5 hour maintaining maximum DOI sample rate.