Patent ID: 7280215

Claim:
An apparatus for evaluating the characteristics of a semiconductor sample, comprising: an intensity-modulated pump beam, said pump beam being focused to a spot on the surface of the sample for periodically exciting the sample, with the intensity and the modulation frequency of the pump beam being sufficient to create thermal and plasma waves in the sample that modulate the optical reflectivity of the sample; a probe beam being directed to a spot on the surface of the sample within a region that has been periodically excited and is reflected therefrom; a wavelength scanning device for scanning a wavelength of the probe beam over a spectral range of at least 100 nm in order to vary the relative contribution of the thermal and plasma waves to the modulation of the optical reflectivity of the sample; a photodetector for measuring the power of the reflected probe beam at a plurality of wavelengths in the spectral range and generating an output signal in response thereto; and a processor operable to receive the output signal and determine a measure of the modulated optical reflectivity of the sample as a function of wavelength.