Patent ID: 6268916
Filing Date: 2001-07-31
Classification: G01B,G01J,G01N

Abstract:
A method for non-destructively measuring properties of a sample, comprising:supplying at least one pump beam of radiation to a surface area of the sample, the intensity of said pump beam varying at at least a first modulation frequency, so that physical properties of the sample are modulated at the first frequency;directing a polarized probe beam of radiation so that the probe beam is modulated at the first frequency by the sample;modulating a polarization state of radiation in the probe beam at at least a second frequency;providing, in response to radiation from the probe beam that has been modulated by the sample and that has been modulated at at least the second frequency, information related to a signal at a difference frequency substantially equal to the difference between the first and the second frequencies or between harmonics of the two frequencies in any combination; andderiving a change in one or more ellipsometric parameters of the sample from the indication.