A method for wavefront measurement of optical imaging system based on grating shearing interferometry, the grating shearing interferometer comprising: a light source and illumination system, an optical imaging system to be tested, a one-dimensional diffraction grating plate, a two-dimensional diffraction grating plate, a two-dimensional photoelectric sensor and a computing unit. The one-dimensional diffraction grating plate and the two-dimensional diffraction grating plate are respectively placed on the object side and the image side of the optical imaging system to be tested. By collecting N sets of interferograms with a $\frac{2\pi }{N}$
phase-shifting interval (where, $N=2\left(\mathrm{fix}\left(\frac{\mathrm{ceil}\left(1/s\right)}{2}\right)+1\right),$
s is the shear ratio of the grating shearing interferometer), combined with a certain phase retrieval algorithm, the influence of all high-order diffraction beams on the phase retrieval accuracy is eliminated, and finally the wavefront measurement accuracy for the optical imaging system is improved.

Method for detecting wavefront aberration for optical imaging system based on grating shearing interferometer, the grating shearing interferometer system comprising a light source and illumination system, an optical imaging system to be tested, a one-dimensional diffraction grating plate, a two-dimensional diffraction grating plate, a two-dimensional photoelectric sensor, and a computing unit. The one-dimensional and two-dimensional diffraction grating plates are respectively placed on the object plane and the image plane of the optical imaging system to be tested. By collecting interferograms with phase-shifting amounts of 0, π/2, π, 3π/2 and N sets of α, π-α, 2π-α (where, $N=2\left(\mathrm{fix}\left(\frac{\mathrm{ceil}\left(1\text{/}s\right)}{2}\right)+1\right),$
s is the shear ratio of the grating shearing interferometer system), combined with a certain phase retrieval algorithm, the influence of all high-order diffraction beams on the phase retrieval accuracy is eliminated, and finally the detection accuracy of wavefront aberration for the imaging system to be tested is improved.

A method of reducing an aberration arising during operation of a lithographic apparatus, the method comprising measuring the aberration to obtain an aberration signal, the aberration signal comprising a first component and a second component, wherein the first component of the aberration signal comprises a first frequency band and the second component of the aberration signal comprises a second frequency band, wherein the first frequency band comprises frequencies that are higher than frequencies comprised in the second frequency band, calculating a correction, wherein a first part of the correction is calculated based on the first component of the aberration signal, and applying the correction to the lithographic apparatus.

A wafer holding device (200, 415) is configured to hold a wafer (205, 416) during operation of a microlithographic projection exposure apparatus and includes at least one sensor that is positionable in different rotational positions.

An exposure method of performing an exposure operation of exposing a substrate via a projection optical system is provided. The method includes executing, in an exposure period in which the exposure operation is performed, aberration correction of the projection optical system to correct an aberration generated by performing the exposure operation, measuring, in a non-exposure period succeeding the exposure period, in which the exposure operation is not performed, an aberration of the projection optical system, and correcting the aberration of the projection optical system using a correction amount adjusted based on a result of the measurement so as to reduce a correction residual in the aberration correction of the projection optical system.

A measurement system (11), the measurement system comprising: a sensor apparatus (22); an illumination system (IL1) arranged to illuminate the sensor apparatus with radiation, the sensor apparatus comprising a patterned region arranged to receive a radiation beam and to form a plurality of diffraction beams, the diffraction beams being separated in a shearing direction; the sensor apparatus comprising a radiation detector (24); wherein the patterned region is arranged such that at least some of the diffraction beams form interference patterns on the radiation detector; wherein the sensor apparatus comprises a plurality of patterned regions (19a-19c, 20a, 20b), and wherein pitches of the patterned regions are different in adjacent patterned regions.

Some implementations described herein provide an exposure tool. The exposure tool includes a reticle deformation detector and one or more processors configured to obtain, via the reticle deformation detector, reticle deformation information associated with a reticle during a scanning process for scanning multiple fields of a wafer. The one or more processors determine, based on the reticle deformation information, a deformation of the reticle at multiple times during the scanning process, and perform, based on the deformation of the reticle at the multiple times, one or more adjustments of one or more components of the exposure tool during the scanning process.

A method of calibrating a projection system heating model to predict an aberration in a projection system in a lithographic apparatus, the method comprising passing exposure radiation through a projection system to expose one or more exposure fields on a substrate provided on a substrate table, making measurements of the aberration in the projection system caused by the exposure radiation, wherein the time period between measurements is less than the time period that would be taken to expose all exposure fields on the substrate.

Embodiments described herein relate to a dynamically controlled lens used in lithography tools. Multiple regions of the dynamic lens can be used to transmit a radiation beam for lithography process. By allowing multiple regions to transmit the radiation beam, the dynamically controlled lens can have an extended life cycle compared to conventional fixed lens. The dynamically controlled lens can be replaced or exchanged at a lower frequency, thus, improving efficiency of the lithography tools and reducing production cost.

A device manufacturing method includes: exposing a first substrate using a lithographic apparatus to form a patterned layer having first features; processing the first substrate to transfer the first features into the first substrate; determining displacements of the first features from their nominal positions in the first substrate; determining a correction to at least partly compensate for the displacements; and exposing a second substrate using a lithographic apparatus to form a patterned layer having the first features, wherein the correction is applied for or during the exposing the second substrate.