A STATISTICALLY BASED MODEL OF ELECTRON-BEAM EXPOSED, CHEMICALLY AMPLIFIED NEGATIVE RESIST

A methodology based on statistically designed factorial experiments has been developed to model the dissolution rate of an electron-beam exposed chemically amplified resist, Shipley SAL-601-ER7, for different post-exposure bake (PEB) and developer concentrations. A statistical experiment of dissolution rate measurements were performed in the Perkin-Elmer development rate monitor using a central composite design with PEB temperature, PEB time, and developer concentration as the factors. These measurements were combined with Monte Carlo simulation of electron energy deposition to generate dissolution rate data as a function of absorbed energy. These data were then fitted to a semiempirical rate equation using nonlinear regression. Statistical analysis of the effects of the three processing factors on the parameters of the rate functions yielded empirical models relating the parameters to the factors. As a result, a rate equation can be determined for any processing conditions, and thus a complete model is obtained for the simulation and optimization of the resist.