Resolution degradation caused by multispur effect in chemically amplified extreme ultraviolet resists

Extreme ultraviolet (EUV) (92.5 eV) radiation is expected as a next-generation exposure source. When EUV photons enter resists, they are absorbed by resist molecules and photoelectrons are emitted. Photoelectrons with the initial energy of approximately 80 eV further induce ionization and generate ion pairs. Because the inelastic mean free path of these electrons is less than 1 nm, ion pairs are so narrowly distributed that they interact with each other through Coulomb forces. In this study, the details in the interaction among ion pairs were investigated by using a Monte Carlo simulation. It was found that the electric interaction between ion pairs significantly degrade the initial acid distribution. The dependence of resolution degradation and multispur effect on acid generator concentration was clarified. The acid generator loading of >10 wt % is effective for the suppression of resolution degradation.