Theoretical estimation of absorption coefficients of various polymers at 13 nm

Abstract

The linear absorption coefficients at 13 nm were calculated for more than 150 polymers. The results indicate that an aromatic substitution lowers the absorption coefficient. This is because oxygen has a larger atomic absorption than carbon or hydrogen and the substitution reduces the relative oxygen content. Furthermore, the Ohnishi parameters for the polymers were calculated in order to investigate the relationship between the absorption at 13 nm and the etching resistance. This showed that polymers with aromatic groups tend to exhibit a lower absorption and a higher etching resistance than those without aromatic groups. This suggests that, regarding resist processes for EUV (extreme ultraviolet) lithography, a single-layer resist process employing no hard-mask layer is another promising candidate in addition to one that uses both an unltrathin resist layer (∼100 nm thick) and a hard-mask layer