Analytical solutions of film profiles and degree of planarization for periodic features during the spin coating process are presented. This article shows that the degree of planarization is independent of Omega(2) and changes slightly with the dimensionless line spacing alpha for Omega(2)> 300. The governing dimensionless parameter Omega(2) represents the ratio of centrifugal force to surface tension force during spin coating. In the cases of low Omega(2) (Omega(2)< 1), the degree of planarization decreases with increasing alpha for a fixed Omega(2). (C) 1999 American Institute of Physics. [S0021-8979(99)05120-8].