Spectrum simulation for semiconductor feature inspection
First Claim
1. A method for determining an unknown parameter of a semiconductor specimen using a semiconductor inspection system, the method comprising:
- scanning a region of interest with an electron beam to cause X-rays to emanate from the region of interest;
detecting the X-rays from the region of interest using at least one X-ray detector wherein the detected X-rays are within a certain energy range spectrum and thereby form an experimental X-ray spectrum;
selecting a reference spectrum from an X-ray spectrum library based upon a set of inspection system parameters, a set of known semiconductor specimen parameters, and an initial estimated value for the unknown parameter;
generating a simulated spectrum using a spectrum simulation algorithm based upon the set of inspection system parameters, the set of known semiconductor specimen parameters, and the initial estimated value for the unknown parameter, wherein the simulated spectrum is generated when an appropriate reference spectrum is not part of the X-ray spectrum library;
comparing the experimental X-ray spectrum against either the reference spectrum or the simulated spectrum and determining the degree to which the experimental X-ray spectrum matches either the reference or simulated spectrum;
when the experimental X-ray spectrum does not match the reference or simulated spectrum to a satisfactory degree, repeating the selecting, generating, and comparing operations wherein a new estimated value for the unknown parameter is used in place of the initial estimated value for the unknown parameter; and
when the experimental X-ray spectrum does match the reference or simulated spectrum to a satisfactory degree, determining that the estimated value for the unknown parameter used to select the reference spectrum or to generate the simulated spectrum is approximately equal to the actual value of the unknown parameter.
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Abstract
Techniques for determining certain parameters of semiconductor specimens using X-ray spectroscopy are described. The invention can be used to determine parameters such as composition, dimensions, and density of semiconductor specimens. Specifically, an X-ray spectrum simulation algorithm is used to iteratively generate a theoretical X-ray spectrum for a semiconductor specimen having certain parameters. The iterative generation of theoretical X-ray spectrums continues until one of the theoretical X-ray spectrum closely matches the actual X-ray spectrum measured off of the specimen. In an alternative embodiment, this technique of generating theoretical X-ray spectrums can be used in combination with a pre-existing library of X-ray spectral signatures for semiconductor specimens having various parameters.
36 Citations
19 Claims
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1. A method for determining an unknown parameter of a semiconductor specimen using a semiconductor inspection system, the method comprising:
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scanning a region of interest with an electron beam to cause X-rays to emanate from the region of interest; detecting the X-rays from the region of interest using at least one X-ray detector wherein the detected X-rays are within a certain energy range spectrum and thereby form an experimental X-ray spectrum; selecting a reference spectrum from an X-ray spectrum library based upon a set of inspection system parameters, a set of known semiconductor specimen parameters, and an initial estimated value for the unknown parameter; generating a simulated spectrum using a spectrum simulation algorithm based upon the set of inspection system parameters, the set of known semiconductor specimen parameters, and the initial estimated value for the unknown parameter, wherein the simulated spectrum is generated when an appropriate reference spectrum is not part of the X-ray spectrum library; comparing the experimental X-ray spectrum against either the reference spectrum or the simulated spectrum and determining the degree to which the experimental X-ray spectrum matches either the reference or simulated spectrum; when the experimental X-ray spectrum does not match the reference or simulated spectrum to a satisfactory degree, repeating the selecting, generating, and comparing operations wherein a new estimated value for the unknown parameter is used in place of the initial estimated value for the unknown parameter; and when the experimental X-ray spectrum does match the reference or simulated spectrum to a satisfactory degree, determining that the estimated value for the unknown parameter used to select the reference spectrum or to generate the simulated spectrum is approximately equal to the actual value of the unknown parameter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for determining an unknown parameter of a semiconductor specimen using a semiconductor inspection system, the method comprising:
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scanning a region of interest with an electron beam to cause X-rays to emanate from the region of interest; detecting the X-rays from the region of interest using at least one X-ray detector wherein the detected X-rays are within a certain energy range spectrum and thereby form an experimental X-ray spectrum; generating a simulated spectrum using a spectrum simulation algorithm based upon a set of inspection system parameters, a set of known semiconductor specimen parameters, and an initial estimated value for the unknown parameter; comparing the experimental X-ray spectrum against the simulated spectrum and determining the degree to which the experimental X-ray spectrum matches the simulated spectrum; when the experimental X-ray spectrum does not match the simulated spectrum to a satisfactory degree, repeating the generating and comparing operations wherein a new estimated value for the unknown parameter is used in place of the initial estimated value for the unknown parameter; and when the experimental X-ray spectrum does match the simulated spectrum to a satisfactory degree, determining that the estimated value for the unknown parameter used to generate the simulated spectrum is approximately equal to the actual value of the unknown parameter. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A computer-readable medium comprising computer code for determining an unknown parameter of a semiconductor specimen using a semiconductor inspection system, the computer-readable medium comprising:
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scanning a region of interest with an electron beam to cause X-rays to emanate from the region of interest; detecting the X-rays from the region of interest using at least one X-ray detector wherein the detected X-rays are within a certain energy range spectrum and thereby form an experimental X-ray spectrum; selecting a reference spectrum from an X-ray spectrum library based upon a set of inspection system parameters, a set of known semiconductor specimen parameters, and an initial estimated value for the unknown parameter; generating a simulated spectrum using a spectrum simulation algorithm based upon the set of inspection system parameters, the set of known semiconductor specimen parameters, and the initial estimated value for the unknown parameter, wherein the simulated spectrum is generated when an appropriate reference spectrum is not part of the X-ray spectrum library; comparing the experimental X-ray spectrum against either the reference spectrum or the simulated spectrum and determining the degree to which the experimental X-ray spectrum matches either the reference or simulated spectrum; when the experimental X-ray spectrum does not match the reference or simulated spectrum to a satisfactory degree, repeating the selecting, generating, and comparing operations wherein a new estimated value for the unknown parameter is used in place of the initial estimated value for the unknown parameter; and when the experimental X-ray spectrum does match the reference or simulated spectrum to a satisfactory degree, determining that the estimated value for the unknown parameter used to select the reference spectrum or to generate the simulated spectrum is approximately equal to the actual value of the unknown parameter. - View Dependent Claims (19)
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Specification