157nm resist material design for improvement of its transparency by using highly precise theoretical calculation

Vacuum ultraviolet (VUV) absorption spectra of resist materials for 157nm lithography were calculated theoretically by symmetry adapted cluster configuration interaction (SAC-CI) method. We have investigated several fluorinated norbornanes. Relatively poor transparencies are calculated in the stereoisomers of difluoronorbornane that are substituted at 1,4 or 7 positions. Furthermore the endo fluorination of norbornane is more effective than the exo fluorination. These results are very useful information for the development of resist materials for 157nm lithography.