APPLICATION OF A REACTION-DIFFUSION MODEL FOR NEGATIVE CHEMICALLY AMPLIFIED RESISTS TO DETERMINE ELECTRON-BEAM PROXIMITY CORRECTION PARAMETERS

The method of single pixel exposures is applied for the determination of acid diffusion effects in negative chemically amplified resists. Th e wide range of crosslink density values contained in a single dot is used to determine nonlinear diffusion parameters. A reaction-diffusion model is developed where the diffusion coefficient D is a function of the crosslink density Theta. This function D(Theta) is evaluated for a given range of postexposure bake parameters in each case and the inf ormation obtained is used for proximity correction, also using the e-b eam lithography simulation tool LITHOS. In order to test the model und er different circumstances, two resists are studied, namely, the comme rcially available SAL-601 and the experimental epoxy novolac resist EP R. The diffusion coefficient is evaluated for each resist under the be st processing conditions. The proximity correction procedure is fully demonstrated in the case of SAL-601. (C) 1996 American Vacuum Society.