Regression analysis of photodecomposable quencher concentration effects on chemical gradient in chemically amplified extreme ultraviolet resist processes

摘要

Chemically amplified resists have been used in the state-of-the-art extreme ultraviolet (EUV) lithography. The basic additive, called a quencher, has been added to the resist formula to control acid diffusion. In this study, the effects of photodecomposable quencher (PDQ) concentration on the chemical gradient (an indicator for line edge roughness) in chemically amplified EUV resist processes were investigated. The chemical gradients were calculated on the basis of the sensitization and reaction mechanisms for different half-pitches, sensitivities, photoacid generator (PAG) concentrations, PDQ concentrations, and the effective reaction radii for deprotection. The obtained 130000 data were analyzed using least squares, lasso, ridge, and elastic net regressions. For the contribution to the chemical gradient, PDQ concentration was apparently symmetrical to PAG concentration. The optimum PDQ concentrations were well predicted within the examined variable ranges even with 495 training data by the fitted parameters obtained through lasso, ridge, and elastic net regressions.