Patent ID: 7619741
Filing Date: 2009-11-17
Classification: G01N

Abstract:
1. An apparatus for evaluating a semiconductor sample comprising: a first light source generating an intensity modulated pump beam having a first wavelength; an optical element for focusing the pump beam onto the surface of the sample to periodically excite a region of the sample in a manner to generate thermal and plasma waves which modulate the optical reflectivity of the sample; a second light source generating a first probe beam having a second wavelength different from the first wavelength, said first probe beam being directed to the sample within the periodically excited region; a third light source generating a second probe beam having a third wavelength different from the first and second wavelengths, said second probe beam being directed to the sample within the periodically excited region; a detector for selectively monitoring one of the first and second probe beams after reflection from the sample and generating output signals in response thereto; a filter for filtering the output signals to isolate the portion of the signal that correspond to the modulated optical reflectivity of the sample; and a processor for selectively activating one of the second and third light sources and for evaluating the sample based on the filtered output signals.