Radiation-Induced Processes in Diazoquinone–Novolac Resist Films under Irradiation with 60Co γ-Rays

Abstract

The processes occurring under the irradiation of FP9120 diazoquinone–novolac resist films on silicon with 60Co γ-rays have been studied by attenuated total reflectance (ATR) FTIR spectroscopy. It has been found that a significant modification of the ATR spectra of the photoresist films was noticeable only at absorbed doses above 200 kGy, and it occurred due to the radiation-induced transformations of methyl, methylene, hydroxymethyl, and phenoxyl groups of phenol–formaldehyde resin and o-naphthoquinone diazide (a photosensitive component). At the same time, the ATR spectra exhibited no signs of the destruction of aromatic fragments in the resist at doses to 300 kGy. In the region of the stretching vibrations of C=O bonds, a decrease in the maximum intensity of a band at ~1700 cm^–1 was observed upon irradiation with its simultaneous broadening and shift to the high-energy region by ~30 cm^–1 due to a change in the nearest environment of the C=O group. An increase in the absorption band intensity at 1650 cm^–1 indicated the accumulation of formaldehyde upon the γ-irradiation of the resist as a result of the fragmentation of hydroxymethyl residues in the phenol–formaldehyde resin.