The mask error factor in optical lithography

摘要: The primary cause of greater than unity mask error factor (MEF) is degradation image integrity. Mathematical description formation reveals the gradual loss shape control by photomask features as critical dimension decreases below 0.8(/spl lambda//NA). growing contribution to line-width variation prompts generalization conventional two-dimensional (2-D) exposure-defocus window (ED window) a three-dimensional (3-D) mask-exposure-defocus volume volume), adding tolerance exposure latitude and depth-of-focus important parameters process. increase in MEF with feature nesting means that relative importance sources changes pattern pitch. Mask improvement most effective reduce for dense features, but lens quality significant affecting sparse patterns. approximately 20% higher dark-field masks, low alternating phase-shifting relatively high assist all have ramifications on lithography strategies printing lines. does not simply indicate need high-quality it also sheds light areas which improvements are needed successful lithography, disciplines cooperate device fabrication.