Annealing concept for the design of environmentally stable chemical amplification resists.

Abstract

Contamination of chemical amplification resists by airborne basic substances can be minimized by reducing the free volume of resist films by annealing. Good annealing requires heating the resist films above their glass transition temperatures. However, it is not usually possible to bake chemical amplification positive resists based on poly(4-hydroxystyrene) above their glass transition temperatures because thermal deprotection typically occurs below their glass transition temperatures. Use of metaisomers to lower glass transition temperatures is described first to prove the validity of our annealing concept. Furthermore, our high temperature bake process of a new thermally and hydrolytically stable positive resist (ESCAP) is reported. The annealing effectively reduces uptake of airborne contaminants by resist films because the diffusivity of small molecules in polymer films is an exponential function of the free volume and thus stabilizes the latent images.