Understanding the effects of photoacid distribution homogeneity and diffusivity on critical dimension control and line edge roughness in chemically amplified resists

Abstract

Resist critical dimension (CD) control and line edge roughness (LER) reduction has been one of the most challenging issues for sub-100nm feature patterning in integrated circuit manufacturing. Among those factors dominating CD and LER, photoacid distribution homogeneity and diffusivity are major elements which are correlated to resist material design and have a direct impact on the lithography performance. In this work, a mesoscale stochastic model has been applied to investigate the joint effect of photoacid distribution homogeneity and diffusivity on resist lithography performance. Simulation results suggest that the high photoacid generator (PAG) loading and low photoacid diffusivity provided by polymer bound-PAG resist systems can provide superior lithography performance as compared to traditional blended-PAG resists, which is in good agreement with our previous experimental characterization of polymer bound-PAG resists. The results also suggest that resist image blur is proportional to the square root of the product of photoacid concentration generated at the line edge and the photoacid diffusion coefficient. LER was observed to be proportional to the product of the standard deviation of the extent of deprotection along the nominal line edge and the reciprocal of the gradient of the deprotection profile along the resist line edge.