Overlay measurement apparatus, lithographic apparatus and device manufacturing method using such overlay measurement apparatus
First Claim
Patent Images
1. An overlay measurement apparatus comprising:
- a polarized light source configured to illuminate a substrate with a polarized light beam;
an optical system configured to capture light reflected by the substrate from the polarized light beam, the optical system comprising;
a first non-polarizing beam splitter configured to receive the polarized light beam from the polarized light source, direct the polarized light beam to the substrate via a projection system, and receive a reflected light beam from the substrate via the projection system, the reflected beam comprising a zeroth order diffraction component;
a second non-polarizing beam splitter configured to receive the reflected light beam from the first non-polarizing beam splitter;
a crossed polarizer configured to receive a portion of reflected light beam from the second non-polarizing beam splitter and transmit an in-plane image and crossed-polarized image;
a blocking element configured to block the in-plane image;
a detector configured to measure an intensity of crossed-polarized image and produce a signal therefrom; and
a processing unit configured to receive the signal from the detector and to process crossed-polarized image for overlay metrology measurement using asymmetry data derived from crossed-polarized image.
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Abstract
An overlay measurement apparatus has a polarized light source for illuminating a sample with a polarized light beam and an optical system to capture light that is scattered by the sample. The optical system includes a polarizer for transmitting an orthogonal polarization component that is orthogonal to a polarization direction of the polarized light beam. A detector measures intensity of the orthogonal polarization component. A processing unit is connected to the detector, and is arranged to process the orthogonal polarization component for overlay metrology measurement using asymmetry data derived from the orthogonal polarization component.
39 Citations
16 Claims
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1. An overlay measurement apparatus comprising:
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a polarized light source configured to illuminate a substrate with a polarized light beam; an optical system configured to capture light reflected by the substrate from the polarized light beam, the optical system comprising; a first non-polarizing beam splitter configured to receive the polarized light beam from the polarized light source, direct the polarized light beam to the substrate via a projection system, and receive a reflected light beam from the substrate via the projection system, the reflected beam comprising a zeroth order diffraction component; a second non-polarizing beam splitter configured to receive the reflected light beam from the first non-polarizing beam splitter; a crossed polarizer configured to receive a portion of reflected light beam from the second non-polarizing beam splitter and transmit an in-plane image and crossed-polarized image; a blocking element configured to block the in-plane image; a detector configured to measure an intensity of crossed-polarized image and produce a signal therefrom; and a processing unit configured to receive the signal from the detector and to process crossed-polarized image for overlay metrology measurement using asymmetry data derived from crossed-polarized image. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A lithographic apparatus, comprising:
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an illumination system configured to produce a beam of radiation; a support configured to support a patterning device that is configured to pattern the beam of radiation; a projection system configured to project the patterned beam onto a substrate; and an overlay measurement system comprising; a polarized light source configured to illuminate the substrate with a polarized light beam; an optical system configured to capture light reflected by the substrate from the polarized light beam, the optical system comprising; a first non-polarizing beam splitter configured to receive the polarized light beam from the polarized source, direct the polarized light beam to the substrate via the protection system, and receive a reflected light beam from the substrate via the projection system, the reflected light beam comprising a zeroth order diffraction component; a second non-polarizing beam splitter configured to receive the reflected light beam from the first non-polarizing beam splitter; a crossed polarizer configured to receive the a portion of reflected light beam from the second non-polarizing beam splitter and transmit an in-plane image and crossed-polarized image; a blocking element configured to block the in-plane image; a detector configured to measure the intensity of crossed-polarized image and produce a signal therefrom; and a processing unit configured to receive the signal from the detector and to process crossed-polarized image for overlay metrology measurement using asymmetry data derived from crossed-polarized image. - View Dependent Claims (9, 10)
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11. A method of measuring overlay comprising:
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illuminating a sample with a polarized light beam; capturing light scattered by the sample from the polarized light beam; transmitting an orthogonal polarization component that is orthogonal to a polarization direction of the polarized light beam; splitting the captured light into an in-plane image and crossed-polarized image; blocking the in-plane image; measuring an intensity of the crossed-polarized image; and performing an overlay metrology measurement using asymmetry data derived from the crossed-polarized image. - View Dependent Claims (12, 13, 14, 15, 16)
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Specification