Determination of acid diffusion parameters and proximity effect correction for highly dense 0.15 mu m features on SAL-601

A new method for the measurement of acid diffusion parameters in negative-tone e-beam chemically amplified resists and its application for proximity effect correction is presented. It is based on the measurement. of the diameter of lithographic features (pillars) obtained from single-pixel e-beam exposures. Generally, long post exposure bake (FEB) times or low post apply bake (PAB) temperatures lead to wider features compared with short PEB times and high PAB temperatures, due to enhanced acid diffusion. The acid diffusion coefficient was found to depend exponentially on cross-linking density. Additionally, proximity effect correction parameters (triple Gaussian parameters) are easily calculated, These parameters are t(PEB) dependent and in the limit (t(PEB) --> 0) are almost equal to the corresponding values for non-amplified resists, The method has been applied to SAL-601 (Shipley), and the calculated proximity parameters were used successfully to correct the proximity effect of complicated layouts with a 0.15 mu m critical dimension.