The use of deep UV resist hardening for high temperature resist-masked processes is becoming more widespread throughout the semiconductor industry. In this report we present data on the wavelength and thermal dependence of the deep UV crosslinking process in novolak resin obtained through dissolution studies and SEM micrographs. An excimer laser was used to provide light of differing wavelengths. The results indicate that longer wavelengths near 308 nm promote crosslinking throughout the 1.5 micron thick resin, while shorter wavelengths induce crosslinking to limited depths. Heating of the wafer during the deep UV exposure is shown to greatly accelerate the crosslinking process, compared to a sequential expose and bake process. SEM micrographs of various stages of hardening in resist are shown. The resist hardening process employed by one commercial system is discussed in terms of the findings of this study.