Investigation of the solvent‐evaporation effect on spin coating of thin films

Abstract A simple empirical relationship exists between the thickness and the solvent‐evaporation rate of spin‐coated thin films. The thickness of a film formed from an organic solvent solution can be approximated by the relationship \documentclass{article}\pagestyle{empty}\begin{document}$ D = K_0 \mu ^{0.36} \omega ^{ - 0.50} (E\lambda /C_p)^{0.60} $\end{document} , where μ is the viscosity of the coating solution, ω is the rotation speed, E is the solvent‐evaporation rate, λ is the latent heat of evaporation, C p is the heat capacity of the solvent, and K 0 is a constant for volatile organic solvents. A similar relationship for aqueous polymer solutions is \documentclass{article}\pagestyle{empty}\begin{document}$ D = K_0 \mu ^{0.36} \omega ^{ - 0.50} (1.0 - RH)^{0.60} $\end{document} , where RH is the relative humidity of air around the spin coater and K a is a constant for aqueous solutions. These relationships are helpful in understanding the mechanism of thin‐film formation in spin coating.