Method and Apparatus for Accurate Calibration of VUV Reflectometer
First Claim
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1. A reflectometer system, comprising:
- a light source that is utilized to create a sample channel light path;
a location in the reflectometer sample channel light path for placement of a standard sample;
a location in the reflectometer for the placement of a reference sample; and
a spectrometer configured to collect reflectance data from the standard sample and the reference sample;
wherein the reflectometer is calibrated by utilizing the presence of significant reflectance variations from the standard sample that result from variations of actual properties of the standard sample from the assumed properties of the standard sample.
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Abstract
A calibration technique is provided that utilizes a standard sample that allows for calibration in the wavelengths of interest even when the standard sample may exhibit significant reflectance variations at those wavelengths for subtle variations in the properties of the standard sample. A second sample, a reference sample may have a relatively featureless reflectance spectrum over the same spectral region and is used in combination with the calibration sample to achieve the calibration. In one embodiment the spectral region may include the VUV spectral region.
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Citations
12 Claims
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1. A reflectometer system, comprising:
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a light source that is utilized to create a sample channel light path; a location in the reflectometer sample channel light path for placement of a standard sample; a location in the reflectometer for the placement of a reference sample; and a spectrometer configured to collect reflectance data from the standard sample and the reference sample; wherein the reflectometer is calibrated by utilizing the presence of significant reflectance variations from the standard sample that result from variations of actual properties of the standard sample from the assumed properties of the standard sample. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A reflection measurement apparatus which operates below deep ultra-violet (DUV) wavelengths, the apparatus comprising:
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at least one light source, the at least one light source providing a source beam including wavelengths below DUV wavelengths; a sample channel light path; a reference channel light path, wherein the reference channel light path is configured to comprise a reference sample that is relatively spectrally featureless in at least some of the vacuum ultra-violet (VUV) wavelength region; a spectrometer that receives light from the sample channel light path and the reference channel light path; and at least one optical element selectively enabling or disabling at least one of the reference channel light path or the sample channel light path; wherein the reflection measurement apparatus is configured to be calibrated by utilizing in the sample channel light path a standard sample that has a significant calibration error function in at least a portion of the VUV wavelength region. - View Dependent Claims (9, 10, 11, 12)
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Specification