Improved CD uniformity for advanced masks using the Sigma7500 pattern generator and ProcessEqualizer(TM)

Abstract:
Managing the total CD error in advanced mask manufacturing requires that error contributions from writing, process and metrology are minimized. This paper describes how both the writing and process contributions have been addressed in the Sigma7500 DUV laser pattern generator, which prints masks by imaging a programmable spatial light modulator (SLM). System enhancements have reduced the writing contribution to global CD uniformity to 5 nm (3s). Processrelated CD error sources, such as the signatures from mask developing and etching can be significant contributors to the total CD error in mask manufacturing. These errors are classified as being either pattern-independent or patterndependent, and the effects of both can be reduced using the ProcessEqualizer feature of the Sigma7500. This software tool performs CD sizing during writing based on pattern density maps derived during mask data preparation, along with tunable parameters that are determined experimentally. The CD sizing function has no effect on system throughput and does not require flattening and re-fracturing of the pattern data.