The soft-baking procedure in photoresist processing is investigated theoretically. A Landau transformation coupled with a finite-difference scheme is adopted to solving the moving-boundary problem under consideration. The experimental data of Shipley SPR5110LA. m-p cresol novolak, poly(methyl methacrylate), Shipley UVIII, and Shipley SNR200 photoresists reported in the literature are analyzed to justify the applicability of the model derived. We show that the concentration dependence of the diffusivecular ty of solvent can have a significant influence on the soft-baking procedure. The rate of transfer of solvent is controlled by the molecular diffusion of solvent in a film.