Spin Coating on Substrate with Topography

Spin coating of a polymer film on a substrate with topography is modeled. Nonnewtonian fluid behavior, solvent diffusivity within coating, and coating leveling are related using this model. The dependence of the coating step height on initial coating concentration, spin speed, feature radial position, and feature dimensions is investigated. For a large feature, the coating profile is dominated by centrifugal force, while for small features the coating profile is dominated by capillary force and the coating is more level. A glassy polymer skin is formed during spinning. The coating profile is then controlled by shrinkage after the skin is formed. The predicted step height is within 10% of that measured experimentally.