Improvement of Alt-PSM Production Process Using Backside Phase Measurement Method

摘要

An alternating phase shift mask (Alt-PSM) enhances resolution and focus margin in wafer print. Therefore it comes into increasing use for device fabrication by KrF and ArF lithography. We have started production of alt-PSMs using quartz etched shifter and single trench structure, which are made by a two-step quartz etching process. This two-step quartz etching process has three writing steps; they are for chrome etching, quartz dry etching and quartz wet etching. We improved alt-PSM production process by using new backside phase measurement method. Consequently phase mean deviation from 180 degree was improved from +/-2.0degree to +/-1.5degree. And process steps reduced from 16 to 12 steps because twice alignment writing became once.