Method and apparatus for using multiple relative reflectance measurements to determine properties of a sample using vacuum ultra violet wavelengths
First Claim
1. A method of measuring properties of a sample under test, comprising:
- providing a reflectometer and at least one reference sample, which is separate from the sample under test, wherein the at least one reference sample is unstable under conditions in which the reflectometer is operated due to a buildup of a contaminant layer on the at least one reference sample during operation of the reflectometer;
collecting a set of data from the sample under test and at least one reference sample; and
utilizing a combination of the sample under test and reference sample data that is independent of incident intensity to determine a property of the sample under test, without calibrating incident reflectometer intensity.
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Accused Products
Abstract
A method and apparatus is disclosed for measuring properties of an unknown sample. A reflectometer and one or more reference pieces is provided. A set of data is collected from the unknown sample and a combination of the reference pieces. A combination of the sample and reference piece data independent of incident intensity is used to determine a property of the unknown sample without calibrating incident reflectometer intensity. The method and apparatus disclosed can measure properties of thin films or scattering structures on semiconductor work pieces. In one embodiment the reflectometer utilizes vacuum ultraviolet (VUV) wavelength reflectometry. Multiple relative reflectance measurements are used to overcome effects of the inevitable contamination buildup that occurs when using optical systems in the VUV region. While advantageous for VUV wavelengths, the method described herein is generally applicable to any wavelength range, and is advantageous in situations where stable reference samples are not available.
146 Citations
39 Claims
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1. A method of measuring properties of a sample under test, comprising:
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providing a reflectometer and at least one reference sample, which is separate from the sample under test, wherein the at least one reference sample is unstable under conditions in which the reflectometer is operated due to a buildup of a contaminant layer on the at least one reference sample during operation of the reflectometer; collecting a set of data from the sample under test and at least one reference sample; and utilizing a combination of the sample under test and reference sample data that is independent of incident intensity to determine a property of the sample under test, without calibrating incident reflectometer intensity. - View Dependent Claims (2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14)
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7. A method of measuring properties of a sample under test, comprising:
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providing a reflectometer and at least one reference sample, wherein the at least one reference sample is unstable under conditions in which the reflectometer is operated; collecting a set of data from the sample under test and at least one reference sample; and utilizing a combination of the sample under test and reference sample data that is independent of incident intensity to determine a property of the sample under test, without calibrating incident reflectometer intensity, wherein the data obtained from the sample under test and the at least one reference sample includes intensity data, wherein the collecting a set of data from the sample under test and at least one reference sample comprises collecting a set of data from the sample under test and a plurality of reference samples, and wherein the reflectance ratios comprise at least one ratio with data from the relatively thick SiO2/Si film structure in the numerator and data from the sample under test in the denominator and another ratio with data from the relatively thick SiO2/Si film structure in the numerator and data from the native SiO2/Si film structure in the denominator.
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15. A system for measuring properties of a sample under test, comprising:
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at least one reference sample, which is separate from the sample under test; a reflectometer configured for collecting a set of data from the sample under test and the at least one reference sample wherein the at least one reference sample is unstable under conditions in which the reflectometer is operated due to a buildup of a contaminant layer on the at least one reference sample during operation of the reflectometer; and a computer operating a software routine configured to utilize a combination of the sample under test and reference sample data that is independent of incident intensity to determine a property of the sample under test, without calibrating incident reflectometer intensity. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A system for measuring properties of a sample under test, comprising:
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at least one reference sample; a reflectometer, configured for collecting a set of data from the sample under test and the at least one reference sample wherein the at least one reference sample is unstable under conditions in which the reflectometer is operated; and a computer operating a software routine that selectably operates in at least one of a plurality of measurement modes, the plurality of measurement modes including at least a first measurement mode and a second measurement mode, wherein, the first measurement mode is configured to utilize a combination of the sample under test and reference sample data that is independent of incident intensity to determine a property of the sample under test, without calibrating incident reflectometer intensity, and the second measurement mode is configured to utilize the reference sample data in a manner that is independent of incident intensity to determine one or more properties of one or more reference pieces, thereby determining the incident intensity of the reflectometer, after which reflectance of samples under test is determinable. - View Dependent Claims (27, 28, 29, 30, 31)
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32. A method of measuring properties of a sample under test, comprising:
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providing a reflectometer and at least one reference sample, wherein the at least one reference sample is unstable under conditions in which the reflectometer is operated; collecting a set of data from the sample under test and at least one reference sample; and selectably operating the system in at least one of a plurality of measurement modes, the plurality of measurement modes including at least a first measurement mode and a second measurement mode, wherein, the first measurement mode is configured to utilize a combination of the sample under test and reference sample data that is independent of incident intensity to determine a property of the sample under test, without calibrating incident reflectometer intensity, and the second measurement mode is configured to utilize the reference sample data in a manner that is independent of incident intensity to determine one or more properties of one or more reference pieces, thereby determining the incident intensity of the reflectometer, after which reflectance of samples under test is determinable. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39)
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Specification