Inspection method and apparatus, and associated computer readable product
First Claim
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1. A method comprising:
- providing a radiation beam with linear polarization;
reflecting the linearly polarized radiation beam off a grating on a substrate at a range of incident and azimuth angles;
introducing a phase shift, by a phase shifter, to the linearly polarized radiation beam thereby altering its polarization to elliptical;
splitting, by a beam splitter, the reflected radiation beam into first and second orthogonally polarized sub-beams;
adjusting at least one of the linearly polarized radiation beam, the grating on the substrate, the phase shifter, and the beam splitter to enable sensitivity to multiple polarization angles and sensitivity to detection of at least one of critical dimension, sidewall angle, and thickness;
shifting a phase of the first sub-beam by a fixed amount with respect to the second sub-beam; and
simultaneously detecting, by a detector, an angle-resolved spectrum of both sub-beams;
wherein the grating and the initial linear polarization of the radiation beam are angled non-orthogonally relative to each other.
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Abstract
A system is configured to measure two separately polarized beams upon diffraction from a substrate in order to determine properties of a grating on a substrate. Linearly polarized light sources are passed via a fixed phase retarder in order to change the phase of one of two orthogonally polarized radiation beams with respect to the other of the two beams. The relative phases of the two radiation beams and other features of the beams as measured in a detector gives rise to properties of the substrate surface. The grating and the initial linear polarization of the radiation beam are angled non-orthogonally relative to each other.
36 Citations
18 Claims
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1. A method comprising:
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providing a radiation beam with linear polarization; reflecting the linearly polarized radiation beam off a grating on a substrate at a range of incident and azimuth angles; introducing a phase shift, by a phase shifter, to the linearly polarized radiation beam thereby altering its polarization to elliptical; splitting, by a beam splitter, the reflected radiation beam into first and second orthogonally polarized sub-beams; adjusting at least one of the linearly polarized radiation beam, the grating on the substrate, the phase shifter, and the beam splitter to enable sensitivity to multiple polarization angles and sensitivity to detection of at least one of critical dimension, sidewall angle, and thickness; shifting a phase of the first sub-beam by a fixed amount with respect to the second sub-beam; and simultaneously detecting, by a detector, an angle-resolved spectrum of both sub-beams; wherein the grating and the initial linear polarization of the radiation beam are angled non-orthogonally relative to each other. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An inspection apparatus comprising:
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a radiation source configured to supply a radiation beam having linear-polarization; an optical element configured to focus the radiation beam onto a substrate at a range of incident and azimuth angles such that the radiation beam reflects from the substrate; a polarizing device configured to polarize the radiation beam into two different polarization directions; a fixed phase-shifter configured to retard a first polarization direction by a predetermined amount so as to impose a fixed phase shift on the reflected radiation beam; a controller configured to adjust at least one of the radiation beam, the substrate, the fixed phase-shifter, and the polarizing device to enable sensitivity to multiple polarization angles and sensitivity to detection of at least one of critical dimension, sidewall angle, and thickness; and a detector system configured to detect simultaneously an angle-resolved spectrum of the two polarization directions of the radiation beam, wherein the apparatus is specifically adapted to make the measurements when a grating on the substrate and the initial linear polarization of the radiation beam are angled non-orthogonally relative to each other. - View Dependent Claims (15, 16)
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17. A non-transitory computer-readable medium having computer program logic recorded thereon, execution of which, by a computing device, causes the computing device to perform operations comprising:
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providing a radiation beam with linear polarization; reflecting the linearly polarized radiation beam off a grating on a substrate at a range of incident and azimuth angles; introducing a phase shift to the linearly polarized radiation beam thereby altering its polarization to elliptical; splitting the reflected radiation beam into first and second orthogonally polarized sub-beams; adjusting one or more of the linearly polarized radiation beam, the grating on the substrate, the phase shifter, and the beam splitter to enable sensitivity to multiple polarization angles and sensitivity to detection of at least one of critical dimension, sidewall angle, or thickness; shifting a phase of the first sub-beams by a fixed amount with respect to the second sub-beam; and simultaneously detecting an angle-resolved spectrum of both sub-beams; wherein the grating and the initial linear polarization of the radiation beam are angled non-orthogonally relative to each other. - View Dependent Claims (18)
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Specification