Patent ID: 6181421
Filing Date: 2001-01-30
Classification: G01J,G01N

Abstract:
An ellipsometer for evaluating a sample, comprising:a light generator that generates a beam of light having a known polarization for interacting with the sample;a compensator formed of an optically uniaxial crystal having a planar front face and a planar rear face that is substantially parallel to the front face, the compensator having an extraordinary axis offset from a normal to the planar front surface at an angle of at least one degree, with the offset angle and the thickness of the compensator being selected to produce a predetermined zero order retardation for a particular wavelength of the beam as the beam passes completely through the compensator;means for rotating the compensator about an axis that is perpendicular to both the front face and to the rear face;an analyzer that interacts with the light beam after the light beam interacts with the sample and with the compensator; anda detector that measures the intensity of the light after the interaction with the analyzer as a function of an angle of the rotation of the compensator about the axis, wherein the measurements correspond to the polarization state of the light impinging on the analyzer.