APPARATUS AND METHODS FOR REDUCING THIN FILM COLOR VARIATION IN OPTICAL INSPECTION OF SEMICONDUCTOR DEVICES AND OTHER SURFACES

摘要

Disclosed are methods and apparatus for designing an optical spectrum of an illumination light beam within an optical inspection system. A set of conditions for inspecting a film on a sample by directing an illumination light beam at the sample is determined. At least a portion of the illumination light beam is reflected off the sample and used to generate an image of at least a portion of the film on the sample. A plurality of peak wavelength values are determined for the optical spectrum of the illumination light beam so as to control color variation in the image of the film portion. The determination of the peak wavelengths is based on the determined set of conditions and a selected thickness range of the film. In one specific embodiment, the color variation is reduced, while in another embodiment the color variation is increased to enhance pattern contrast. An apparatus which implements the designed optical spectrum is also disclosed.