Modified Acetal Approach to 157nm Resist Design

Optical absorbance data on a variety of acetal-derivatized hydroxystyrene based polymers are reported at 157nm. Acetals based on tertiary butyl, cyclohexyl ethyl and a silicon-derivative show improved transparency of the corresponding polymers compared with the parent hydroxystyrene backbone. Silicon-acetal demonstrated capability to resolve 80nm dense trenches in a bilayer resist system. No silicon outgassing was observed upon 157nm exposure. The resist also displayed excellent O2/SO2-etch properties.