Inspection apparatus for lithography
First Claim
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1. An inspection apparatus comprising:
- an optical element configured to focus a 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 reflected radiation beam into two different polarization directions;
a variable retarder configured to retard at least one of the two different polarization directions by a certain amount so as to apply a variable phase shift on the reflected radiation beam, the variable phase shift being dependent on a wavelength of the radiation beam; and
a detector system configured to detect simultaneously an angle-resolved spectrum of the two different polarization directions of the radiation beam.
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Abstract
The measurement of two separately polarized beams (Ix, Iy) upon diffraction from a substrate (W) in order to determine properties of the substrate is disclosed. Circularly or elliptically polarized radiation is passed via a variable 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 phase change is dependent on the wavelength of the polarized beam. 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.
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Citations
20 Claims
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1. An inspection apparatus comprising:
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an optical element configured to focus a 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 reflected radiation beam into two different polarization directions; a variable retarder configured to retard at least one of the two different polarization directions by a certain amount so as to apply a variable phase shift on the reflected radiation beam, the variable phase shift being dependent on a wavelength of the radiation beam; and a detector system configured to detect simultaneously an angle-resolved spectrum of the two different polarization directions of the radiation beam. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method comprising:
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providing a radiation beam with elliptical polarization; reflecting the radiation beam off the surface of a substrate; splitting the reflected radiation beam into two polarized sub-beams; shifting a phase of a first sub-beam of the two sub-beams by a variable amount with respect to the second sub-beam of the two sub-beams, the variable amount being dependent on the wavelength of the radiation beam; and simultaneously detecting the sub-beams. - View Dependent Claims (15, 16, 17, 18)
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19. A lithographic apparatus comprising:
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an optical element configured to focus a 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 reflected radiation beam into two different polarization orientations; a variable retarder with a variable phase shift configured to shift a phase of the reflected radiation beam, the variable phase shift being dependent on the wavelength of the radiation beam; and a detector system configured to detect simultaneously an angle-resolved spectrum of the two polarization orientations of the radiation beam.
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20. A lithographic cell comprising:
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a radiation source configured to supply a radiation beam; an optical element configured to focus a 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 reflected radiation beam into two different polarization orientations; a variable retarder with a variable phase shift configured to shift a phase of the reflected radiation beam, the variable phase shift being dependent on the wavelength of the radiation beam; and a detector system configured to detect simultaneously an angle-resolved spectrum of the two polarization orientations of the radiation beam.
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Specification