The percolation approach to the development of pulsed laser exposed positive photoresists

Results of photolithography experiments utilizing the XeCl excimer laser and positive photoresists are reported. Abrupt reciprocity loss resulting in the growth of photoresist contrast and sensitivity was found when laser pulse energy density exceeded a threshold value of about 50 mJ/cm2. Percolation theory is used to derive a model of resist thickness remaining versus dose for development of pulse exposed photoresist. The model accurately describes the change in dissolution of AZ2400 photoresist when the energy is delivered in multiple versus single pulse exposures.