Patent ID: 7215419

Claim:
A method of calibrating a wafer inspection tool, said wafer inspection tool including a polychromatic light source for generating a probe beam which illuminates a sample and a spectrometer for measuring the probe beam as a function of wavelength after reflection from the sample, said inspection tool including a moveable optics system for directing the probe beam onto the sample, said method comprising the steps of: moving the optics system over a calibration wafer to scan measurement points on the wafer with the polychromatic light from the probe beam; measuring the calibration wafer at a plurality of discrete wavelengths over a range of wavelengths simultaneously using the spectrometer at each of a plurality of discrete positions of the optics system; determining and storing position and wavelength related calibration information; and using the calibration information to correct for position variations of the optics system when measuring a test wafer using the spectrometer.