Patent ID: 7889340
Filing Date: 2011-02-15
Classification: G01J,G01N

Abstract:
1. A normal incidence ellipsometer apparatus comprising: a light source configured to generate a polychromatic light beam characterized by a range of optical wavelengths; a polarizer optically coupled to the illumination source and configured to impart a known polarization state to the light beam before the light beam interacts with a sample; a first compensator disposed in the path of the light beam configured to induce phase retardations of a polarization state of the light beam, wherein the first compensator is configured such that at least a first effective phase retardation value is induced over a first range of wavelengths by the first compensator, wherein a first effective phase retardation value is within a range of effective retardations; a second compensator disposed in the path of the light beam configured to induce phase retardations in a polarization state of the light beam before the probe beam is incident on the sample along an optical path normal to the sample, wherein the second compensator is configured such that at least a second effective phase retardation value is induced over a second range of wavelengths by the second compensator, wherein the second range of wavelengths is complementary to the first range of wavelengths, and wherein the second effective phase retardation value is within the range of effective retardations; each of said first and second compensators being rotatable about an axis substantially parallel to the propagation direction of the light beam; and a detector configured to interact with a portion of the light beam that interacts with the sample and with said first and second compensators, wherein the detector is configured to measure an intensity of light as a function of wavelength and of a rotation angle of each of the first and second compensators about its respective axis.