Inspection apparatus for lithography
First Claim
1. An inspection apparatus comprising:
- a radiation source configured to supply a radiation beam;
an optical element configured to focus the radiation beam onto a substrate;
a beam splitter system configured to split the radiation once reflected from the substrate into at least four components having different polarization orientations;
a focusing system configured to focus the four components at different positions on a detector, the detector configured to detect simultaneously angle-resolved spectra of the four components of the radiation beam;
a processor configured to use the angle-resolved spectra of the four components to determine a phase difference between polarization directions and a ratio between polarization direction amplitudes of the reflected radiation beam; and
an iterative loop device configured to determine a refractive index, an absorption index, and a thickness of a resist layer on the substrate based on a difference between the determined phase difference and a modeled phase difference and based on a difference between the determined ratio and a modeled ratio.
1 Assignment
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Accused Products
Abstract
Four separately polarized beams are simultaneously measured upon diffraction from a substrate (W) to determine properties of the substrate. Linearly, circularly or elliptically polarized radiation is transmitted through a first beam splitter (N-PBS) and split into two polarized beams. These two beams are further split into two further beams using two further beam splitters, the further beam splitters (32,34) being rotated by 45° with respect to each other. The plurality of polarizing beam splitters enables the measurement of the intensity of all four beams and thus the measurement of the phase modulation and amplitude of the combined beams to give the features of the substrate. Algorithms are used to compare the four intensities of each of the polarized angles to give rise to the phase difference between the polarization directions and the ratio between the two main polarization direction amplitudes of the original polarized beam.
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Citations
23 Claims
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1. An inspection apparatus comprising:
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a radiation source configured to supply a radiation beam; an optical element configured to focus the radiation beam onto a substrate; a beam splitter system configured to split the radiation once reflected from the substrate into at least four components having different polarization orientations; a focusing system configured to focus the four components at different positions on a detector, the detector configured to detect simultaneously angle-resolved spectra of the four components of the radiation beam; a processor configured to use the angle-resolved spectra of the four components to determine a phase difference between polarization directions and a ratio between polarization direction amplitudes of the reflected radiation beam; and an iterative loop device configured to determine a refractive index, an absorption index, and a thickness of a resist layer on the substrate based on a difference between the determined phase difference and a modeled phase difference and based on a difference between the determined ratio and a modeled ratio. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method comprising:
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reflecting an elliptically polarized radiation beam off a surface of a substrate; splitting the reflected radiation beam into first and second elliptically polarized sub-beams; splitting the first sub-beam into first and second components with polarization orientations of about 0 and 90 degrees respectively; splitting the second sub-beam into third and fourth components with polarization orientations of about 45 and 135 degrees respectively; focusing the first, second, third, and fourth components at different position on a detector; simultaneously detecting the first, second, third and fourth components using the detector; using angle-resolved spectra of the four polarization orientations to determine a phase difference between polarization directions and a ratio between polarization direction amplitudes of the reflected radiation beam; and iteratively determining a refractive index, an absorption index, and a thickness of a resist layer on the substrate using a difference between the determined phase difference and a modeled phase difference and using a difference between the determined ratio and a modeled ratio. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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22. A lithographic apparatus comprising:
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a radiation source configured to supply a radiation beam; an optical element configured to focus the radiation beam onto a substrate; a beam splitter configured to split the radiation beam once reflected from the substrate into at least four components having different polarization orientations; a focusing system configured to focus the four components at different positions on a detector, the detector configured to detect simultaneously angle-resolved spectra of the four components of the radiation beam; a processor configured to use the angle-resolved spectra of the four components to determine a phase difference between the polarized radiation directions and a ratio between polarization direction amplitudes of the reflected radiation beam; and an iterative loop device configured to determine a refractive index, an absorption index, and a thickness of a resist layer on the substrate based on a difference between the determined phase difference and a modeled phase difference and based on a difference between the determined ratio and a modeled ratio.
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23. A lithographic cell comprising:
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a radiation source configured to supply a radiation beam; an optical element configured to focus the radiation beam onto a substrate; a beam splitter configured to split the radiation beam once reflected from the substrate into at least four components having different polarization orientations; a focusing system configured to focus the four components at different positions on a detector, the detector configured to detect simultaneously angle-resolved spectra of the four components of the radiation beam; a processor configured to determine a phase difference between the polarized radiation directions and a ratio between polarization direction amplitudes of the reflected radiation beam; and an iterative loop device configured to determine a refractive index, an absorption index, and a thickness of a resist layer on the substrate based on a difference between the determined phase difference and a modeled phase difference and based on a difference between the determined ratio and a modeled ratio.
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Specification