Optical Metrology With Small Illumination Spot Size
First Claim
1. A metrology system comprising:
- an illumination source configured to generate an amount of illumination light;
an illumination optics subsystem configured to direct the amount of illumination light from the illumination source to a specimen under measurement, wherein the illumination optics subsystem includes;
a spatial light modulator disposed in a path of the illumination light from the illumination source to the specimen under measurement, wherein the spatial light modulator is configured to modulate amplitude, phase, or a combination of amplitude and phase across the path of the illumination light;
a detector configured to generate a plurality of output signals indicative of a response of the specimen to the amount of illumination light; and
a collection optics subsystem configured to collect an amount of collected light from the surface of the specimen and direct the amount of collected light to the detector.
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Accused Products
Abstract
Methods and systems are presented to reduce the illumination spot size projected onto a measurement target and associated spillover onto area surrounding a measurement target. In one aspect, a spatial light modulator (SLM) is located in the illumination path between the illumination light source and the measurement sample. The SLM is configured to modulate amplitude, phase, or both, across the path of the illumination light to reduce wavefront errors. In some embodiments, the desired state of the SLM is based on wavefront measurements performed in an optical path of the metrology system. In another aspect, an illumination aperture having an image plane tilted at an oblique angle with respect to a beam of illumination light is employed to overcome defocusing effects in metrology systems that employ oblique illumination of the measurement sample. In some embodiments, the illumination aperture, objective lens, and specimen are aligned to satisfy the Scheimpflug condition.
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Citations
30 Claims
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1. A metrology system comprising:
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an illumination source configured to generate an amount of illumination light; an illumination optics subsystem configured to direct the amount of illumination light from the illumination source to a specimen under measurement, wherein the illumination optics subsystem includes; a spatial light modulator disposed in a path of the illumination light from the illumination source to the specimen under measurement, wherein the spatial light modulator is configured to modulate amplitude, phase, or a combination of amplitude and phase across the path of the illumination light; a detector configured to generate a plurality of output signals indicative of a response of the specimen to the amount of illumination light; and a collection optics subsystem configured to collect an amount of collected light from the surface of the specimen and direct the amount of collected light to the detector. - 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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receiving an amount of illumination light from an illumination source; modulating an amplitude profile, a phase profile, or both the amplitude profile and the phase profile across a path of the illumination light from the illumination source to a surface of a specimen under measurement; directing an amount of collected light from the surface of the specimen to a detector; and generating a plurality of output signals from the collected light, wherein the output signals are indicative of a response of the specimen to the amount of modulated illumination light. - View Dependent Claims (16, 17, 18, 19)
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20. A metrology system comprising:
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an illumination source configured to generate an amount of illumination light; an illumination optics subsystem configured to direct the amount of illumination light from the illumination source to a specimen under measurement, wherein the illumination optics subsystem includes an illumination aperture having an image plane oriented at an oblique angle with respect to a beam of the illumination light passing through the illumination aperture; a detector configured to generate a plurality of output signals indicative of a response of the specimen to the amount of illumination light; and a collection optics subsystem configured to collect an amount of collected light from the surface of the specimen and direct the amount of collected light to the detector. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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Specification