Surface roughness development during photoresist dissolution

The minimization of nanoscale roughness in patterned images has become a pr iority for the process of photolithography in the production of microproces sors. In order to probe the molecular basis for surface roughness, the deve lopment of photoresist has been simulated through application of the critic al-ionization model to a three-dimensional molecular lattice representation of the polymer matrix. The model was adapted to describe chemically amplif ied photoresists of the sort now commonly used in microlithography. Simulat ions of the dependence of the dissolution rate and surface roughness on the degree of polymerization, polydispersity, and fractional deprotection agre e with experimental results. Changes in surface roughness are shown to corr elate with the length of the experimentally observed induction period. Mode l predictions for the effect of void fraction and developer concentration o n roughness are also presented. Observations of differences in the effect o f developer concentration on top-surface and sidewall roughness are explain ed by a critical development time predicted by the simulation. (C) 1999 Ame rican Vacuum Society. [S0734-211X(99)06704-9].