Effect of microstructure on deprotection kinetics in photoresist

This article describes the result of predictions based on a novel continuum model for the effect of microstructure on deprotection reaction kinetics during postexposure bake (PEB). The effect of neighboring blocking groups is incorporated in a continuum PEB model. Provided blocking groups with neighbors react at a slower rate than isolated blocking groups, an up to 8% improvement in latent image contrast is predicted. In addition, a first principles calculation of the equilibrium structure for poly(methyl methacrylate-co-t-butyl methyl methacrylate) copolymer with acid present is reported. Hybrid quantum mechanics/molecular mechanics (QC/MM) results indicate that a strong hydrogen bond forms between blocked and unblocked neighbor sites in the presence of acid. The QC/MM prediction provides evidence confirming the rate constant for deprotection reaction with a neighboring blocked site is reduced relative to isolated blocking groups. The new PEB model form is shown to improve the fit to kinetic Fourier tran...