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US 2026/0071918 A1Published application
Methods and system for determining aberrations of a projection system
AssigneeASML Netherlands B.V.
InventorPaul Jean Maurice GEELEN
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Abstract
Methods, and corresponding systems for, determining one or more aberrations of a projection system (for example a projection system of a lithographic apparatus) are disclosed. One method includes performing a phase stepping or phase scanning process using a first patterning device (at object level) that includes a specular diffraction grating. Also disclosed is a calibration method for determining calibration data which characterizes any differences between: aberrations of a projection system determined using a diffusive grating at object level and aberrations of a projection system determined using a specular grating at object level.
Claims21
A method of determining one or more aberrations of a projection system, the method comprising:
- performing a phase stepping or phase scanning process, the phase stepping or phase scanning process comprising:
- illuminating a first patterning device with illumination radiation, wherein the first patterning device comprises a specular diffraction grating arranged to form a plurality of first diffraction beams, the first diffraction beams being separated in a shearing direction;
- projecting, with the projection system, at least part of the plurality of first diffraction beams onto a sensor apparatus, the sensor apparatus comprising:
- a second patterning device arranged to receive the first diffraction beams from the projection system and to form a plurality of second diffraction beams from each of the first diffraction beams;
- and
- a radiation detector arranged to receive at least a portion of the second diffraction beams;
- and
- moving the first and/or second patterning device in the shearing direction such that an intensity of radiation received by each part of the radiation detector that receives radiation varies as a function of the movement in the shearing direction so as to form an oscillating signal;
- and
- determining one or more aberrations of the projection system from the oscillating signals determined by each part of the radiation detector that receives radiation.
7 more elements
A calibration method comprising:
- performing a phase stepping or phase scanning process using an object-level specular diffraction grating so as to generate one or more oscillating signals;
- determining one or more aberrations of a projection system from the one or more oscillating signals;
- performing an additional phase stepping or phase scanning process using an object-level diffusive diffraction grating so as to generate one or more additional oscillating signals;
- determining one or more additional aberrations of the projection system from the one or more additional oscillating signals;
- and
- determining calibration data which characterizes any differences between:
- (a) the determined one or more aberrations of the projection system;
- and (b) the determined one or more additional aberrations of the projection system.
5 more elements
A measurement system comprising:
- a first patterning device comprising a specular diffraction grating;
- a sensor apparatus comprising a second patterning device and a radiation detector, the first patterning device and the sensor apparatus being positionable such that a projection system can form an image of the first patterning device on the second patterning device with illumination radiation and such that the radiation detector is arranged to receive the illumination radiation after it has passed via the second patterning device;
- a positioning apparatus configured to move the first patterning device and/or the sensor apparatus;
- and
- a controller configured to:
- control the positioning apparatus so as to move the first patterning device and/or the sensor apparatus in a shearing direction such that an intensity of radiation received by each part of the radiation detector varies as a function of the movement in the shearing direction so as to form an oscillating signal;
- determine, from the radiation detector, a phase of a harmonic of the oscillating signal at a plurality of positions on the radiation detector;
- and
- determine at least one coefficient that characterizes at least one aberration of the projection system from the phase of a harmonic of the oscillating signal at the plurality of positions on the radiation detector.
6 more elements
(canceled)
A non-transitory computer-readable medium comprising instructions stored therein, the instructions, when executed by a computer system, configured to cause the computer system to at least:
- cause performance of a phase stepping or phase scanning process, the phase stepping or phase scanning process comprising:
- illumination of a first patterning device with illumination radiation, wherein the first patterning device comprises a specular diffraction grating arranged to form a plurality of first diffraction beams, the first diffraction beams being separated in a shearing direction;
- projection, with a projection system, at least part of the plurality of first diffraction beams onto a sensor apparatus, the sensor apparatus comprising:
- a second patterning device arranged to receive the first diffraction beams from the projection system and to form a plurality of second diffraction beams from each of the first diffraction beams;
- and
- a radiation detector arranged to receive at least a portion of the second diffraction beams;
- and
- movement of the first and/or second patterning device in the shearing direction such that an intensity of radiation received by each part of the radiation detector that receives radiation varies as a function of the movement in the shearing direction so as to form an oscillating signal;
- and
- determine one or more aberrations of the projection system from the oscillating signals determined by each part of the radiation detector that receives radiation.
7 more elements
Dependencies are inferred from the claim text.