Calibration method, detection system, exposure apparatus, article manufacturing method, and non-transitory computer-readable storage medium
A calibration method of a detection system including an illumination system configured to illuminate a detection target, and an imaging system configured to form an image of light from the detection target on a photoelectric conversion element, the method including obtaining, for each of at least two combinations of first apertures in the illumination system and second apertures in the imaging system, each of which is formed by selecting one first aperture and one second aperture from the plurality of first apertures and the plurality of second apertures, a defocus characteristic indicating a shift amount of the image on the photoelectric conversion element with respect to a defocus amount of the detection target in a state in which each of the first aperture and the second aperture is positioned in a first position shifted from a reference position.
1. A calibration method of a detection system including an illumination system configured to illuminate a detection target, and an imaging system configured to form an image of light from the detection target on a photoelectric conversion element, wherein
the illumination system includes a plurality of first apertures selectively arranged in a pupil plane of the illumination system and having different openings,
the imaging system includes a plurality of second apertures selectively arranged in a pupil plane of the imaging system and having different openings, and
the calibration method comprises:
obtaining, for each of at least two combinations of first apertures and second apertures, each of which is formed by selecting one first aperture and one second aperture from the plurality of first apertures and the plurality of second apertures a first defocus characteristic indicating a shift amount of the image on the photoelectric conversion element with respect to a defocus amount of the detection target in a state in which each of the first aperture and the second aperture is positioned in a first position shifted from a reference position, and
performing position adjustment on each of the first aperture and the second aperture such that each of the first aperture and the second aperture is positioned in the reference position, based on a reference defocus characteristic indicating a shift amount of the image on the photoelectric conversion element with respect to a defocus amount of the detection target in a state in which each of the first aperture and the second aperture is positioned in the reference position, and on the first defocus characteristic obtained in the obtaining,
wherein in the performing the position adjustment, a driving amount of each of the first aperture and the second aperture required for the position adjustment is obtained from a difference between the first defocus characteristic and the reference defocus characteristic, and from a fluctuation amount of the reference defocus characteristic when the first aperture and the second aperture are fluctuated by a unit amount in the pupil plane of the illumination system and the pupil plane of the imaging system.
2. The method according to claim 1 , wherein the reference defocus characteristic and the fluctuation amount of the reference defocus characteristic are obtained in advance before the obtaining is performed.
3. The method according to claim 1 , wherein the first aperture arranged in the pupil plane of the illumination system and the second aperture arranged in the pupil plane of the imaging system have perfectly circular openings having central positions overlapping each other and different radii.
4. The method according to claim 1 , wherein
the at least two combinations include a first combination and a second combination, and
an opening ratio of a first aperture, of the plurality of first apertures, included in the first combination to a first aperture, of the plurality of first apertures, included in the second combination is not less than twice.
5. The method according to claim 1 , wherein
the at least two combinations include a first combination and a second combination,
a second aperture, of the plurality of second apertures, included in the first combination is also included as the second aperture, of the plurality of second apertures, included in the second combination, and
the second aperture included in the first combination and in the second combination has an opening radius larger than an opening radius of a first aperture, of the plurality of first apertures, included in the first combination and a first aperture, of the plurality of first apertures, included in the second combination.
6. The method according to claim 1 , wherein the light is light including at least two types of wavelength bands of not less than 450 nm.
7. The method according to claim 1 , wherein the detection target includes a structure configured to generate diffracted light in only one of two directions perpendicular to each other in a plane perpendicular to an optical axis of the detection system.
8. The method according to claim 1 , wherein the reference position includes an initial position in which a position of each of the first aperture and the second aperture is adjusted such that a lateral shift amount and asymmetry of the image formed on the photoelectric conversion element when the detection target is defocused fall within allowable ranges.
9. A non-transitory computer-readable storage medium storing a program for causing a computer to execute the calibration method defined in claim 1 .
10. A detection system for detecting a position of a detection target, comprising:
an illumination system configured to illuminate the detection target;
an imaging system configured to form an image of light from the detection target on a photoelectric conversion element; and
a processing unit configured to perform a process of calibrating the detection system, wherein
the illumination system includes a plurality of first apertures selectively arranged in a pupil plane of the illumination system and having different openings,
the imaging system includes a plurality of second apertures selectively arranged in a pupil plane of the imaging system and having different openings, and
the processing unit obtains, for each of at least two combinations of first apertures and second apertures, each of which is formed by selecting one first aperture and one second aperture from the plurality of first apertures and the plurality of second apertures, a first defocus characteristic indicating a shift amount of the image on the photoelectric conversion element with respect to a defocus amount of the detection target in a state in which each of the first aperture and the second aperture is positioned in a first position shifted from a reference position, and
performs position adjustment on each of the first aperture and the second aperture such that each of the first aperture and the second aperture is positioned in the reference position, based on a reference defocus characteristic indicating a shift amount of the image on the photoelectric conversion element with respect to a defocus amount of the detection target in a state in which each of the first aperture and the second aperture is positioned in the reference position, and on the first defocus characteristic,
wherein in the position adjustment performed by the processing unit, a driving amount of each of the first aperture and the second aperture required for the position adjustment is obtained from a difference between the first defocus characteristic and the reference defocus characteristic, and from a fluctuation amount of the reference defocus characteristic when the first aperture and the second aperture are fluctuated by a unit amount in the pupil plane of the illumination system and the pupil plane of the imaging system.
11. An exposure apparatus for exposing a substrate, comprising:
a detection system defined in claim 10 and configured to detect a mark formed on the substrate as a detection target; and
a control unit configured to adjust a position of the substrate based on a position of the mark detected by the detection system.
12. An article manufacturing method comprising:
exposing a substrate using an exposure apparatus defined in claim 11 ;
developing the exposed substrate; and
manufacturing an article from the developed substrate.