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US 7,889,339 B1Granted
Complementary waveplate rotating compensator ellipsometer
AssigneeKLA-Tencor Corporation
InventorsKlaus Flock, Jeff T. Fanton
Life of this patent
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Abstract
Ellipsometry using two waveplates of complementary retardation in a dual rotating compensator configuration is disclosed. Two waveplates of complementary retardation may be used to increase the useful spectral range of a rotating compensator ellipsometer, in particular towards the deep Ultraviolet (UV) spectrum. The improved rotating compensating ellipsometer disclosed herein enables a user to select specific and different waveplate retardations for the purpose of increasing the operating wavelength range of the rotating compensating ellipsometer.
Claims50
A rotating compensator broadband spectroscopic ellipsometer for evaluating a sample comprising:
- a light source configured to generate a polychromatic light beam characterized by a range of useful wavelengths and a known polarization;
- a first compensator assembly disposed along an optical path of the light beam and a second compensator assembly disposed along the optical path of the light beam, wherein one or both of said first and second compensator assemblies includes a waveplate that is rotatable about an axis substantially parallel to a propagation direction of the light beam
- wherein the first compensator assembly is configured to induce at least a first effective phase retardation value of a polarization state of the light beam over a first range of wavelengths, wherein the first effective phase retardation value is within a range of effective retardations
- wherein the second compensator assembly is configured to induce at least a second effective phase retardation value of a polarization state of the light beam over a second range of wavelengths, 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;
- an analyzer configured to interact with a portion of the light beam that interacts with the sample and with said first and second compensators;
- and
- a detector optically coupled to the analyzer, wherein the detector is configured to measure an intensity of light after interaction with the analyzer as a function of wavelength and of a rotation angle of each of the first and second compensators about its respective axis.
4 more elements
A method of analyzing a sample comprising the steps of:
- a) generating a beam of light with a useful range of wavelength constituents and known polarization;
- b) inducing a phase retardation between two polarization states of the beam of light using first and second compensator assemblies,
- wherein the first compensator assembly induces phase retardations within a specified range of retardations over a first portion of the useful range of wavelengths,
- wherein the second compensator assembly induces phase retardations within the specified range of retardations over a second portion of the useful range of wavelengths, wherein the second portion is at least partially complementary to the first portion;
- c) rotating a waveplate of one or both of the first and second compensator assemblies about an axis substantially parallel to a propagation direction of the beam of light;
- d) subjecting the light beam to interaction with an analyzer after interaction with both the first and second compensator assemblies and the sample;
- and
- e) measuring an intensity of useful wavelength constituents of the light beam after interaction with the analyzer as a function of compensator azimuth.
5 more elements
An apparatus for evaluating a sample comprising:
- means for generating a beam of polychromatic light having a range of wavelengths and a known polarization for interacting with the sample;
- a first compensating means for inducing phase retardations of a polarization state of the light beam over a first range of wavelengths, wherein the first compensating means and the first range of wavelengths are selected such that at least a first effective phase retardation value induced over the first range of wavelengths lies within a range of effective phase retardations;
- a second compensating means for inducing phase retardations of a polarization state of the light beam over a second range of wavelengths, wherein the second range of wavelengths is out side of and complementary to the first range of wavelengths, wherein the second range of wavelengths and the second compensating means are selected such that at least a second effective phase retardation value induced over the second range of wavelengths lies within the range of effective phase retardations;
- each of said first and second compensating means being rotatable about an axis substantially parallel to the propagation direction of the light beam;
- an analyzing means for interacting with the light beam after the light beam interacts with the sample and with said first and second compensating means;
- and detecting means for measuring the intensity of the light after the interaction with the analyzing means as a function of wavelength and of a rotation angle of each of the first and second compensating means about its respective axis, including light intensities of those wavelengths corresponding to said first and second wavelength ranges.
3 more elements
Dependencies are inferred from the claim text.