Apodization measurement for lithographic apparatus
AssigneeASML Netherlands B.V.
InventorsMarcus Adrianus Van De Kerkhof, Haico Victor Kok
Life of this patent
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Abstract
A method and apparatus are provided for measuring the apodization of projection optics for use in a lithographic apparatus, the projection optics having an object plane where, in use, a reticle is placed, a pupil plane, and an image plane where, in use, a wafer is placed. The method includes placing one or more Appropriate apertures in said object plane for creating a substantially uniform light distribution, illuminating the or each aperture and measuring the intensity distribution at a plane which is conjugate to the pupil plane in order to calculate the apodization of the projection optics.
Claims20
A method of measuring apodization of projection optics for use in a lithographic apparatus, the projection optics having an object plane where, in use, a patterning device is located, a pupil plane, and an image plane where, in use, a substrate is located, the method comprising:
- placing an aperture in said object plane to create a substantially uniform radiation distribution;
- illuminating the aperture in said object plane;
- measuring an intensity distribution at a plane which is conjugate to the pupil plane in order to calculate the apodization of the projection optics;
- placing an aperture at the image plane of said projection optics to create a substantially uniform radiation distribution;
- placing a sensor behind said aperture at the image plane seen from the projection optics in a plane out of focus with respect to the image plane of said projection optics;
- and
- calibrating the angular sensitivity of said sensor.
Apparatus for measuring an optical characteristic of projection optics for use in a lithographic apparatus, the projection optics having an object plane where, in use, a patterning device is located, a pupil plane, and an image plane where, in use, a substrate is located, the apparatus comprising:
- an aperture locatable or located in said object Plane, the aperture configured to create a substantially uniform radiation distribution;
- a sensor configured to measure an intensity distribution of illumination from the aperture at a plane which is conjugate to the pupil plane to determine the optical characteristic of the projection optics based on the measured intensity distribution:
- and
- an aperture locatable or located between the projection optics and the sensor to calibrate the angular sensitivity of the sensor.
A lithographic apparatus comprising:
- an illumination system configured to condition a beam of radiation;
- a support structure configured to support a patterning device, the patterning device serving to impart the projection beam with a pattern in its cross-section;
- a substrate table configured to hold a substrate;
- projection optics configured to project the patterned beam onto a target portion of the substrate and having an object plane, where, in use, the patterning device is located, a pupil plane, and an image plane where, in use, the substrate is located;
- an aperture locatable or located in said object plane, the aperture configured to create a substantially uniform radiation distribution;
- a sensor configured to measure the intensity distribution at a plane which is conjugate to the pupil plane to determine an optical characteristic of the projection optics based on the measured intensity distribution;
- and
- an aperture locatable or located between the projection optics and the sensor to calibrate the angular sensitivity of the sensor.
Dependencies are inferred from the claim text.