Evaluation of resists outgassing by EUV irradiation

Extreme ultraviolet (EUV) lithography requires a vacuum environment: for exposure. Therefore the understanding of the outgassing hydrocarbon ion species of the photoresist becomes important. Contamination due to the hydrocarbons affects the optics of the EUV tool such as the reflectivity of the mask and the imaging mirror. We discuss here of the outgassing dependence of resist polymer structure and solvent type under the EUV irradiation. The resist components require photochemical stability and low evaporating species for EUV lithography. The Methacryl backboned polymer has indicated larger outgassing value rather than PHS backboned polymer, which due to the quaternary carbon induced de-polymerization reaction. The main reaction is seemed to be due to the ester structure decomposed reaction. The selection of the basic polymer structure, ester ratio in the backbone and protecting group are very important for a low outgassing resist design. Our results show resist which contain PGME, MAK, and MMP as the solvent, have lower outgassing characteristics under the EUV irradiation. This characteristic is own to the low residual solvent content in resist film prior to the EUV irradiation. As for results, the high annealing type CA resist based on the PHS polymer and PGME solvent have the lowest outgassing characteristics under the EUV irradiation.