Investigation of the properties of thick photoresist films

Process simulation and modeling techniques have demonstrated significant success in predicting the behavior of optical lithography for semiconductor processes with photoresist thicknesses below 2 microns. An extension of these same principles and methods has been applied to thick resist process up to 10 microns. This study examines the use of simulation analysis in conjunction with experimental results to study the effects of photoresist film thickness and photoresist properties on lithographic performance. The simulation results examine various photoresist model parameters and their impact on typical lithographic process indicators such as depth of focus and exposure latitude. These results show the importance of the photoresist absorption parameter A (micrometers -1) and the developer selectivity n in determining lithographic performance. High values of n provide increased process latitude, while low values of A reduce the required exposure energy.