Therma-wave, Inc.

Joanne Yu Man Law

David E Aspnes

An ellipsometer for evaluating a sample includes a light generator that generates a beam of light having a known polarization for interacting with the sample. A polarimeter of the ellipsometer includes a compensator, an analyzer and a detector. The compensator is formed of an optically uniaxial material. The compensator has a planar front face, and a planar rear face that is substantially parallel to the front face. The compensator is configured such that one ordinary axis of the crystal, but not the second ordinary axis of the crystal, lies in the plane of the front face. The compensator is positioned in the path of the light beam such that the light beam is normally incident to the front face of the compensator. As such, the ordinary ray is not displaced as it passes through the compensator. The ellipsometer further includes means for rotating the compensator about an axis that is perpendicular to both the front face and to the rear face. The analyzer interacts with the light beam after the light beam interacts with the sample and with the compensator. The detector 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. The measurements can be used to determine the change in polarization state that occurs as light is reflected from the sample.

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Fremont, CA, United States of America

Joanne Yu Man Law