When a thin dielectric film placed between two semi-infinite media is irradiated with monochromatic plane waves, a standing wave is produced in the film. An analytical expression for the standing wave intensity within the film is derived. This expression is then expanded to include the effects of other dielectric films on either side of the film or an inhomogeneous film. Applications of these expressions are given for photolithographic modeling.
Chris A. Mack, "Analytical expression for the standing wave intensity in photoresist," Appl. Opt. 25, 1958-1961 (1986)