Process endpoint detection method using broadband reflectometry
First Claim
1. A method of determining a parameter of interest during processing of a patterned substrate, comprising:
- obtaining a measured net reflectance spectrum resulting from illuminating at least a portion of the patterned substrate with a light beam having a broadband spectrum;
calculating a modeled net reflectance spectrum as a weighted incoherent sum of reflectances from different regions constituting the portion of the patterned substrate. for wavelengths below a selected transition wavelength in the broadband specrum using a first optical model to calculate the reflectance from each region as a weighted coherent sum of reflected fields from thin film stacks corresponding to laterally distinct areas constituting the region;
for wavelengths above the selected transition wavelength in the broadband spectrum, using a second optical model to calculate the reflectance frown each region as a reflected field from a thin film stack obtained by replacing layers in the region with effective homogeneous mediums; and
determining a set of parameters that provides a close match between the measured net reflectance spectrum and the modeled net reflectance spectrum.
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Abstract
A method of determining a parameter of interest during processing of a patterned substrate includes obtaining a measured net reflectance spectrum resulting from illuminating at least a portion of the patterned substrate with a light beam having a broadband spectrum, calculating a modeled net reflectance spectrum as a weighted incoherent sum of reflectances from different regions constituting the portion of the patterned substrate, and determining a set of parameters that provides a close match between the measured net reflectance spectrum and the modeled net reflectance spectrum. For wavelengths below a selected transition wavelength, a first optical model is used to calculate the reflectance from each region as a weighted coherent sum of reflected fields from thin film stacks corresponding to laterally distinct areas constituting the region. For wavelengths above the transition wavelength, a second optical model based on effective medium approximation is used to calculate the reflectance from each region.
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Citations
18 Claims
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1. A method of determining a parameter of interest during processing of a patterned substrate, comprising:
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obtaining a measured net reflectance spectrum resulting from illuminating at least a portion of the patterned substrate with a light beam having a broadband spectrum;
calculating a modeled net reflectance spectrum as a weighted incoherent sum of reflectances from different regions constituting the portion of the patterned substrate. for wavelengths below a selected transition wavelength in the broadband specrum using a first optical model to calculate the reflectance from each region as a weighted coherent sum of reflected fields from thin film stacks corresponding to laterally distinct areas constituting the region;
for wavelengths above the selected transition wavelength in the broadband spectrum, using a second optical model to calculate the reflectance frown each region as a reflected field from a thin film stack obtained by replacing layers in the region with effective homogeneous mediums; and
determining a set of parameters that provides a close match between the measured net reflectance spectrum and the modeled net reflectance spectrum. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method of controlling processing of a patterned substrate, comprising:
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obtaining a measured net reflectance spectrum resulting from illuminating at least a portion of the patterned substrate with a light beam having a broadband spectrum;
calculating a modeled net reflectance spectrum as a weighted incoherent sum of reflectances from different regions constituting the portion of the patterned substrate;
for wavelengths below a selected transition wavelength in the broadband spectrum, using a first optical model to calculate the reflectance from each region as a weighted coherent sum of reflected fields from thin film stacks corresponding to laterally distinct areas constituting the region;
for wavelengths above the selected transition wavelength in the broadband spectrum using a second optical model to calculate the reflectance from each region as a reflected field from a thin film stack obtained by replacing layers in the region with effective homogeneous mediums;
determining a set of parameters that provides a close match between the measured net reflectance spectrum and the modeled net reflectance spectrum;
deriving a parameter of interest from the set of parameters; and
signaling an endpoint in the processing of the patterned substrate if the value of the parameter of interest satisfies a predetermined endpoint criterion.
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Specification