METHODS AND APPARATUS FOR MEASURING THE THICKNESS OF A FILM, PARTICULARLY OF A PHOTORESIST FILM ON A SEMICONDUCTOR SUBSTRATE

摘要

A method and apparatus for measuring lateral variations in the thickness or in the refractive index of a transparent film such as photoresist on a substrate such as a semiconductor wafer. The film is illuminated by a beam of light including multiple wavelengths. A signal representing a variation of the intensity of the light reflected from the film at the various wavelengths is decomposed into principal frequencies, and the lateral variations in the thickness or in the refractive index of the film is inferred from these principal frequencies. Lateral thickness variation measurements are used in real time for controlling the application or removal of the film.