Film measurement system with improved calibration
First Claim
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1. A method for measuring one or more films of a sample, comprising the steps of:
- directing a beam of broadband radiation towards the sample such that radiation from the beam modified by the sample includes at least one persistent wavelength marker;
detecting intensity of radiation of spectral components from the beam that is modified by the sample to measure the one or more films at a plurality of wavelengths in the broadband simultaneously by means of a first detector array of multiple pixels, said array having been calibrated with respect to a calibration function and having a prior pixel position of the marker associated with the calibration function;
determining a current pixel position of the at least one persistent wavelength marker from the beam that is modified by the sample; and
correcting said calibration by reference to said prior and current pixel positions of the at least one persistent wavelength marker.
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Abstract
The pixel position-to-wavelength calibration function of film measurement devices such as spectroscopic ellipsometers and spectroreflectometers may shift due to temperature and humidity changes and mechanical factors. One or more wavelength markers provided by the light source or reference sample may be used to correct the calibration function. The pixel positions of one or more persistent wavelength markers are noted during the calibration process and the current positions of such markers are again noted to account for shifts due to various factors to correct the calibration function.
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Citations
25 Claims
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1. A method for measuring one or more films of a sample, comprising the steps of:
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directing a beam of broadband radiation towards the sample such that radiation from the beam modified by the sample includes at least one persistent wavelength marker; detecting intensity of radiation of spectral components from the beam that is modified by the sample to measure the one or more films at a plurality of wavelengths in the broadband simultaneously by means of a first detector array of multiple pixels, said array having been calibrated with respect to a calibration function and having a prior pixel position of the marker associated with the calibration function; determining a current pixel position of the at least one persistent wavelength marker from the beam that is modified by the sample; and correcting said calibration by reference to said prior and current pixel positions of the at least one persistent wavelength marker. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for measuring one or more films of a sample, comprising the steps of:
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directing a first beam of radiation towards a reference sample, said reference sample being such that radiation from the beam modified by the reference sample includes at least one persistent wavelength marker; determining a current pixel position of said marker at a detector array of multiple pixels and a difference between the current and a prior pixel position of said marker at said detector array; correcting a pixel position-to-wavelength calibration of said detector array by reference to said difference; directing a second beam of broadband radiation towards the sample; detecting radiation from the second beam that is modified by the sample; and providing a measurement of the one or more films at a plurality of wavelengths in the broadband simultaneously by means of the detector array of multiple pixels and in reference to the corrected calibration. - View Dependent Claims (12, 13, 14)
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15. An apparatus for measuring one or more films of a sample, comprising:
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means for directing a beam of broadband radiation towards the sample such that radiation from the beam modified by the sample includes at least one persistent wavelength marker; a first detector array of multiple pixels detecting radiation from the beam that is modified by the sample to measure the one or more films at a plurality of wavelengths in the broadband simultaneously, said array having been calibrated with respect to a calibration function and having a prior pixel position of the marker associated with the calibration function; means for determining a current pixel position of the at least one persistent wavelength marker from the beam that is modified by the sample; and means for correcting said calibration by reference to said prior and current pixel positions of the at least one persistent wavelength marker. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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22. An apparatus for measuring one or more films of a sample, comprising:
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a reference sample; means for directing a beam of radiation towards the reference sample, said reference sample being such that radiation from the beam modified by the reference sample includes at least one persistent wavelength marker; means for determining a current pixel position of said marker; means for correcting a pixel position-to-wavelength calibration of a detector array of multiple pixels by reference to the current pixel position and a prior pixel position of said marker at the detector array; means for directing a beam of radiation towards the sample, said beam including broadband radiation, wherein the detector array of multiple pixels detects radiation from the beam that is modified by the sample; and means for providing a measurement of the one or more films at a plurality of wavelengths in the broadband simultaneously by reference to the corrected calibration. - View Dependent Claims (23, 24, 25)
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Specification