A Systematic Approach for I-line Manufacturing Process Optimization

Abstract

A framework for process optimization and characterization was discussed and applied to the development of an 0.8μm i-line lithography process for CMOS manufacturing. Response surface and characterization data were presented. Metrics for process optimization were discussed. Depth of focus windows for i-line and g-line lithography were compared for resist materials of similar capability run with optimized processes. Depth of focus data on 3 different stepper types were used to draw conclusions: a 0.38 NA g-line and 0.40 NA i-line from Manufacturer 1, and a 0.48 NA g-line from Manufacturer 2. I-line resists from 2 different manufacturers were seen to have similar depth of focus characteristics. Maintaining acceptable wall angle for the resist profile was found to be a more severe constraint on the depth of focus than maintaining critical dimension control. The i-line resist offered better wall angle than g-line resist, but less global process stability. At center of field, i-line lenses and currently available i-line resists have effectively 10 to 20% more depth of focus than g-line lenses and g-line resists at comparable resolution.