The effect of prebake (PB) temperature on chemical structure and removal by wet ozone of the photo-active compound (PAC) positive-tone novolak resin/diazonaphthoquinone by use of FT-IR, micro-sampling mass spectrometry (mu-MS) and thermogravimetry analyzer (TGA). Resist films prebaked at between 100 degrees C and 200 degrees C were completely removable by wet ozone, but the resist removal rate decreased with increasing PB temperature and decreased significantly between 140 degrees C and 160 degrees C. The FT-IR spectrum revealed desorption of N-2 from the PAC near the PB temperature of 160 degrees C. On the other hand, the novolak resin did not change with PB temperature. The mu-MS results confirmed that the decomposition temperature of the novolak resin and PAC did not change with changes in PB temperature. TGA curves indicated that the amount of the solvent remaining in the resist film was substantially desorbed at PB temperatures between 140 degrees C and 160 degrees C. From these results, we concluded that the chemical structure and thermal cross-linking of the resist are not affected by changes in the PB temperature. In contrast, the evaporation of residual solvents in the resist film increases with increasing PB temperature, resulting in shrinkage of the film. The decrease in resist removal rate of about 60% between 140 degrees C and 160 degrees C was therefore concluded to be due to the curing of the film.