Analysis of Outgassing from EUV Resists

Outgassing evaluations of polyhydroxystyrene (PHS) based chemically amplified EUV positive photoresist was performed. As a result, the strong dependencies of outgassing increase to various process conditions such as pre-bake temperature and time, resist film thickness and pre-exposure retarding time in vacuum were understood. Of these process conditions, the most significant process factor was known to be the variation of pre-bake temperature. It was concluded that the main cause of such variations were the effect of residual solvent in the photoresist film. From a re-analysis of the mass spectrum, outgassing components released during EUV exposure have been observed and classified into two general types of release trends; fast and slow reaction rate components. Fast reaction rate components were assumed to have originated from photoresist photo-acid generator (PAG) (48amu and 64amu). On the other hand, slow reaction rate components assumed to be mostly CxHy, have been speculated to originate from the decomposition of the photoresist protecting group after reaction with the released photoacids of PAG. Based on these results, the further analysis of photoresist outgassing release mechanisms upon EUV exposure was made possible.