Time dependent simulation of acid and product distributions in chemically amplified resists

In KrF or ArF resist processing, a chemically amplified resist is widely used for ULSI device fabrication. Due to the catalytic reaction of generated acid, decomposition of a positive resist or cross linking of a negative resist is amplified during post-exposure baking. In order to take into account these characteristics during resist simulation, a resist simulator based upon the percolation theory is developed, and the acid and product distributions during post exposure baking are iteratively calculated. Thus, we can conclude that the acid and product distribution in resist film are time dependent. Moreover, it is necessary to develop using percolation theory a resist simulator that can take into account macroscopic feature changes from microscopic molecular structural change. The dissolution rate curve and distribution of acid diffusion length are derived with percolation theory. Then the distribution of the product that corresponds to decomposition in a positive resist is calculated. When the increase the acid thermal diffusion enough to reduce the standing wave effect while keeping it small enough not to reach neighboring patterns, the contour lines of product distribution from the thermal catalyst reaction move vertically father than horizontally. (This is not a molecule movement.) By using these features, the resist rectangularity is improved and the DOF is chemically enlarged.