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

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 {article}{empty}{document}D = K₀ μ 0.36 ω - 0.50 (Eλ /Cₚ)0.60{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 {article}{empty}{document}D = K₀ μ 0.36 ω - 0.50 (1.0 - RH)0.60{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.