Numerical analysis of the spin-coating process

The effects of solvent evaporation and non-Newtonian characteristics on the flow of polymer solutions on a flat rotating disk were analyzed theoretically and numerically. The solvent evaporation was evaluated from species conservation. The power-law and Carreau models were used for the non-Newtonian characteristics. The dependency of the dry-film thickness on the initial concentration of solute predicted by the Newtonian fluids agreed well with the reported experimental data. The thickness predicted decreased with the −0.658th power of spin speed for Newtonian fluids and decreased faster with the −2/(2n+1) power for power-law fluids, where n<1 is the power-law index, in contrast to most experimental values of about −0.5. The Carreau model predicted a similar value as for Newtonian fluids. To resolve the discrepancy between the theoretical prediction and experimental data, the mass transfer coefficient from liquid to vapor was assumed to increase the pth power of spin speed, as assumed by Meyerhofer [J. Appl. Phys. 49, 3993 (1978)]. The choice of the value of p then successfully explained various the experimental data.