Study of proximity lithography simulations using measurements of dissolution rate and calculation of the light intensity distributions in the photoresist

This report describes the results of a study on resist profile simulation in proximity printing, using light intensity distribution and actually measured dissolution rate values, a method that takes the gap effect into consideration (the effect of the distance between mask and wafer on the aerial image and resist profiles). We calculate the light intensity distribution with the gap effect based on the Van Cittert-Zernike theory and on the Hopkins equation as a model of light intensity distribution of proximity printing in resist film. Dissolution rate values are obtained using an apparatus to measure resist film thickness during development. The resist profile simulation is carried out using the combined data thus obtained. To verify the validity of this simulation, we use an SEM to observe resist profiles obtained from a diazonaphthoquinone (DNQ)-novolak resin positive-type resist for thick films, varying the proximity gaps using the mask aligner, which uses light in the broadband wavelengths of 350 mm to 450 mm, and compare the results with the simulation. The results of simulation and those of the SEM observation are in agreement, proving the validity of our method.