An apparatus (2) that performs high resolution thickness metrology on a thin film layer of a wafer (24), includes a filtered white light source that forms a collimated monochromatic light beam (19). The filtered white light source includes a halogen lamp (10), a condensing lens (12), a circular aperture...http://www.google.com/patents/US5543919?utm_source=gb-gplus-sharePatent US5543919 - Apparatus and method for performing high spatial resolution thin film layer thickness metrology
