Theoretical calculations of photoabsorption of molecules in the vacuum ultraviolet region

The theoretical design of transparent materials for use as photoresist materials for F 2 lithography (157 nm) requires molecular orbital calculations of the photoabsorption of molecules in the vacuum ultraviolet (VUV) region. To predict photoabsorption, this study employed ab initio molecular orbital calculations at the level of single-excitation configuration interaction (CIS) combined with an empirical correction to the calculated peak position. This method was used to calculate the photoabsorption spectra of various functional groups, such as alcohol, ether, ketone, carboxylic acid and ester groups, as well as several polymers and alicyclic groups. On the basis of the calculation results, the applicability of these functional groups to photoresists for F 2 lithography is discussed.