Patent ID: 7423757

Claim:
An apparatus for evaluating a semiconductor sample comprising: first, second and third lasers each for generating an output beam at a different wavelength; optical elements for focusing the output beams collinearly onto the sample; a modulator coupled to said first and second lasers; a detector for monitoring the reflected portion of a non-modulated beam and generating output signals in response thereto that correspond to the modulated optical reflectivity of the sample; a filter for filtering the output signals; and a processor for controlling the modulator to selectively modulate one of the first and second lasers to operate as a pump beam to generate thermal and plasma waves in the semiconductor sample which modulate the optical reflectivity of the sample and wherein either the other of the first and second lasers or the third laser functions as a non-modulated probe beam and wherein the processor functions to evaluate the sample based on the filtered output signals.