Inventors:
Yu Guan - San Jose CA
Hong Fu - Fremont CA
Steven R. Lange - Alamo CA
Assignee:
KLA-Tenor Corporation - San Jose CA
International Classification:
G01N 2188
US Classification:
3562374, 3562371, 3562372, 3562373, 3562375, 250205, 25055926
Abstract:
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.