Spin coating of thin and ultrathin polymer films

The spin coating of thin (> 200 nm thick) and ultrathin (< 200 nm thick) po lymer films is examined in several solvents of varying volatility over a br oad range of polymer solution concentrations and spin speeds. Experimentall y measured film thicknesses are compared with a simple model proposed by Bo rnside, Macosko, and Scriven, which predicts film thickness based on the in itial properties of the polymer solution, solvent, and spin speed. This mod el is found to predict film thickness values within 10% over the entire ran ge of conditions explored, which gave film thicknesses from 10 nm to 33 mu m. The model underpredicts film thickness for cases in which a very volatil e solvent is used or the initial concentration of polymer is high, while ov erpredicting film thickness for cases in which a low volatility solvent is used or the initial polymer concentration is very low. These deviations are a consequence of how the model decouples fluid flow and solvent evaporatio n.