Abstract
In chemically amplified extreme ultraviolet (EUV) resists, the thermalization distance of secondary electrons is a major cause of the degradation of the original EUV aerial image and increases the line edge roughness (LER). However, the longer the thermalization distance is, the more acid generators are decomposed. As the acid concentration increases, the acid diffusion length required for the polarity change of resist polymers decreases. With the reduction in diffusion length, the resolution blur induced by acid diffusion is suppressed. In this study, we investigated the optimum thermalization distance for obtaining the best latent image quality. The optimum thermalization distance for 32 nm line-and-space patterns was 7 nm at 10 wt% acid generator (TPS-tf) concentration. The optimum thermalization distance decreased with the half-pitch of line-and-space patterns. For 11 nm half-pitch, the optimum thermalization distance was 3 nm, which is approximately the same as that in the poly(4-hydroxystyrene) matrix.
