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US 7,460,237 B1Granted
Inspection method and apparatus, lithographic apparatus, lithographic processing cell and device manufacturing method
AssigneeASML Netherlands B.V.
InventorHugo Augustinus Joseph Cramer
Life of this patent
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Abstract
In a method of determining a structure parameter of a target pattern in a lithographic process, a series of calibration spectra are calculated from a reference pattern. Spectral analysis is performed on each calculated spectra, the spectral components and associated weighting being derived and stored in a library or used as the basis of an iterative search method. A spectrum is measured from the target pattern and spectral analysis of the measured spectrum is performed. The derived weighting factors of the principal components are compared with the weighting factors of the measured spectrum to determine the structure parameter.
Claims16
A method of determining a structure parameter of a target pattern in a lithographic process used to manufacture a device layer on a substrate, the method comprising:
- calculating a series of calibration spectra from a reference pattern, each spectra being calculated using a different known value of a structure parameter of the reference pattern;
- performing spectral analysis on each calculated calibration spectra, for a selected number of points of the spectra, to obtain a common set of spectral components and a plurality of first sets of weighting factors, each first set of weighting factors representing one calculated spectrum;
- measuring a target spectrum produced by directing a beam of radiation onto the target pattern;
- performing spectral analysis on the measured target spectrum using the common set of spectral components obtained from the spectral analysis of the calculated calibration spectra to obtain a second set of weighting factors representing the measured target spectrum;
- comparing a representation of the first set of weighting factors and a representation of the second set of weighting factors;
- and
- using the comparison to derive a value for the structure parameter of the target pattern.
4 more elements
An inspection apparatus configured to determine a value of a parameter of a lithographic process used to manufacture a device layer on a substrate, the apparatus comprising:
- a calculation system arranged to calculate a series of calibration spectra from a reference pattern, each spectra being calculated using a different known value of a structure parameter of the reference pattern;
- a first analysis system arranged to perform spectral analysis on each calculated calibration spectra, for a selected number of points of the spectra, to obtain a common set of spectral components and a plurality of first sets of weighting factors, each first set of weighting factors representing one calculated spectrum;
- a measurement system arranged to direct a beam of radiation onto a target pattern on a substrate and to measure the spectrum;
- a second analysis system arranged to perform spectral analysis on the measured spectrum using the common set of spectral components obtained from the spectral analysis of the calculated calibration spectra to obtain a second set of weighting factors representing the measured spectrum;
- a comparison arrangement arranged to compare a representation of the first set of weighting factors and a representation of the second set of weighting factors;
- and
- a derivation arrangement arranged to use the output of the comparison arrangement to derive the value for the parameter of the lithographic process.
4 more elements
A lithographic apparatus, comprising:
- an illumination optical system arranged to illuminate a pattern;
- a projection optical system arranged to project an image of a pattern onto a substrate;
- and
- an inspection apparatus configured to determine a value of a parameter of a lithographic process used to manufacture a device layer on a substrate, the apparatus comprising:
- a calculation system arranged to calculate a series of calibration spectra from a reference pattern, each spectra being calculated using a different known value of a structure parameter of the reference pattern,
- a first analysis system arranged to perform spectral analysis on each calculated calibration spectra, for a selected number of points of the spectra, to obtain a common set of spectral components and a plurality of first sets of weighting factors, each first set of weighting factors representing one calculated spectrum,
- a measurement system arranged to direct a beam of radiation onto a target pattern on a substrate and to measure the spectrum,
- a second analysis system arranged to perform spectral analysis on the measured spectrum using the common set of spectral components obtained from the spectral analysis of the calculated calibration spectra to obtain a second set of weighting factors representing the measured spectrum,
- a comparison arrangement arranged to compare a representation of the first set of weighting factors and a representation of the second set of weighting factors, and
- a derivation arrangement arranged to use the output of the comparison arrangement to derive the value for the parameter of the lithographic process.
7 more elements
A lithographic cell comprising;
- a coater arranged to coat a substrate with a radiation sensitive layer;
- a lithographic apparatus arranged to expose an image onto the radiation sensitive layer of a substrate coated by the coater;
- a developer arranged to develop an image exposed by the lithographic apparatus;
- and
- an inspection apparatus configured to determine a value of a parameter of a lithographic process used to manufacture a device layer on a substrate, the apparatus comprising:
- a calculation system arranged to calculate a series of calibration spectra from a reference pattern, each spectra being calculated using a different known value of a structure parameter of the reference pattern,
- a first analysis system arranged to perform spectral analysis on each calculated calibration spectra, for a selected number of points of the spectra, to obtain a common set of spectral components and a plurality of first sets of weighting factors, each first set of weighting factors representing one calculated spectrum,
- a measurement system arranged to direct a beam of radiation onto a target pattern on a substrate and to measure the spectrum,
- a second analysis system arranged to perform spectral analysis on the measured spectrum using the common set of spectral components obtained from the spectral analysis of the calculated calibration spectra to obtain a second set of weighting factors representing the measured spectrum,
- a comparison arrangement arranged to compare a representation of the first set of weighting factors and a representation of the second set of weighting factors, and
- a derivation arrangement arranged to use the output of the comparison arrangement to derive the value for the parameter of the lithographic process.
8 more elements
A computer program for implementing a method of determining a structure parameter of a target pattern in a lithographic process used to manufacture a device layer on a substrate, the method comprising:
- calculating a series of calibration spectra from a reference pattern, each spectra being calculated using a different known value of a structure parameter of the reference pattern;
- performing spectral analysis on each calculated calibration spectra, for a selected number of points of the spectra, to obtain a common set of spectral components and a plurality of first sets of weighting factors, each first set of weighting factors representing one calculated spectrum;
- performing spectral analysis on a spectrum measured from a target, using the common set of spectral components obtained from the spectral analysis of the calculated calibration spectra to obtain a second set of weighting factors representing the measured spectrum;
- comparing a representation of the first set of weighting factors and a representation of the second set of weighting factors;
- and
- using the comparison to derive a value for the structure parameter of the target pattern.
3 more elements
Dependencies are inferred from the claim text.