Outgassing Characteristics of Low-Molecular-Weight Resists for Extreme Ultraviolet Lithography

Abstract

We discuss the outgassing characteristics under extreme ultraviolet (EUV) exposure for a new resist system based on amorphous low-molecular-weight (Mw) polyphenols consisting of 4,4'-methylenebis[2-[di(2-methyl-4-hydroxy-5-cyclohexylphenyl)]methyl] phenol (3M6C-MBSA) compared with polyhydroxystyrene. (PHOST) The outgassing characteristics of the photoresist based on the PHOST resin were better than those of the photoresist based on 3M6C-MBSA as the base material. However, when the same polymer was reacted with a protecting group, the outgassing characteristics were reversed. The decomposition reaction mechanism under EUV exposure is discussed on the basis of results from both mass spectrometry and FT-IR measurements. The results indicate that the reactions of 3M6C-MBSA (Resist B) and PHOST (Resist D) under EUV exposure have different mechanisms. It was confirmed that the decomposition of the molecular backbone is the main reaction for 3M6C-MBSA, whereas the decomposition of the protective group is the main reaction for PHOST.