Predictive Three‐Dimensional CFD Modeling of Evaporation‐Coupled PVDF/DMF Spin‐Coating on Finite Square Substrates

Predictive thickness control remains challenging for spin‐coated polymer films on finite, noncircular substrates, particularly with solvent evaporation. This study presents a three‐dimensional computational fluid dynamics framework to simulate poly(vinylidene fluoride) dissolved in dimethylformamide during spin‐coating on a finite square substrate. The model resolved free‐surface hydrodynamics, interfacial solvent evaporation, species transport, and concentration‐dependent viscosity to capture evaporation‐coupled thinning dynamics. The simulation results were corrected with a dry‐film equation based on mass conservation to obtain the film profiles. Two simulated cases—nonevaporating and evaporating—were investigated for three parameters—spin‐coating time, rotational speed, and solution concentration. The nonevaporating model was validated against the one‐dimensional analytical solution, while the evaporating model was validated against experimental values. Both the simulated and experimental thicknesses exhibited good quantitative agreement, confirming that the model accurately captured the film formation mechanisms. Remaining discrepancies were attributed to liquid retention at the substrate edge, uncertainty in initial dispensed volume, and numerical resolution effects near the interfacial regions. The model revealed that evaporation‐induced viscosity evolution significantly modified thinning behavior, particularly at low speeds and high concentrations, and amplified edge accumulation on finite substrates. This work establishes a predictive framework for thickness and profile control in spin‐coated polymer films.