Modeling of Novolak-based positive photoresist exposed to KrF excimer laser UV radiation at 248 nm

A model is presented for calculating the local exposure and the development rate for a Novolak-resin naphtoquinone-diazide sensitized photoresist exposed to a KrF excimer laser UV radiation at 248 nm. The measured transmission of the pulsed UV radiation through the resist is presented and compared to the simulated one using the model. Classical bleaching characteristics (i.e. the resist transmittance increases with the dose) are observed at low dose exposure with low energy per pulse. When the dose is increased, the photoresist transmittance reaches a maximum and starts to decrease. This behavior is assumed to be due to UV radiation effect on the resin. The model describes a general photoresist with absorbing components, each with two distinctive initial and postexposure states. The model is applied to the case of a Novolak-based photoresist where the two components are the photoactive compound and the resin