Aberrations of a projection lens for microlithography can be subdivided into two classes: a first class of aberrations, which are distinguished by virtue of the fact that their future size increases by a non-negligible value after a constant time duration, independently of their current size, and a second class of aberrations, which, after reaching a threshold, only increase by a negligible value after each further time duration. An adjustment method is proposed, which adjusts these two classes of aberrations in parallel in time with one another.

A projection exposure apparatus includes a projection lens, a wavefront manipulator and a wavefront measuring device for measuring a wavefront in the projection lens. The wavefront measuring device includes a Moiré grating arrangement having an object grating and an image grating which are designed to be arranged in an object plane and an image plane, respectively, of the projection lens. The object grating and the image grating are coordinated with one another in a manner true to scale in such a way as to generate a Moiré superimposition pattern from an imaging of the object grating onto the image plane and the image grating. The Moiré grating arrangement is designed in such a way as to simultaneously generate the Moiré superimposition pattern for a plurality of field points of an object field in the object plane and/or of an image field in the image plane.

A method of metrology target design is described. The method includes determining a sensitivity of a parameter for a metrology target design to an optical aberration, determining the parameter for a product design exposed using an optical system of a lithographic apparatus, and determining an impact on the parameter of the metrology target design based on the parameter for the product design and the product of the sensitivity and one or more of the respective aberrations of the optical system.

A test object for measuring the point spread function (PSF) of an optical system having a given Airy diameter (d.sub.Airy) comprises a structure to be imaged having a plurality of structure elements to be imaged, wherein the structure elements are embodied and arranged in such a way that the structure has at least two axes of symmetry.

A method of patterning substrates using a lithographic apparatus. The method comprising providing a beam of radiation using an illumination system, using a patterning device to impart the radiation beam with a pattern in its cross-section, and using a projection system to project the patterned radiation beam onto target portions of a lot of substrates, wherein the method further comprises performing a radiation beam aberration measurement after projecting the patterned radiation beam onto a subset of the lot of substrates, performing an adjustment of the projection system using the results of the radiation beam aberration measurement, then projecting the patterned radiation beam onto a further subset of the lot of substrates.

A method for ascertaining distortion properties of an optical system in a measurement system for microlithography is provided, wherein the optical system images at least one structure to be measured into a measurement image. In accordance with one aspect, a method according to the invention comprises the following steps: measuring the field-dependent image aberrations of the optical system; determining a first distortion pattern present in the first image field generated by the optical system during measurement of at least one predefined structure; carrying out an optical forward simulation for the predefined structure taking account of the field-dependent image aberrations measured previously, with a second image field being generated; determining a second distortion pattern for the second image field generated previously; and ascertaining the structure-independent distortion properties of the optical system by calculating a third distortion pattern as the difference between the first distortion pattern and the second distortion pattern.

A method includes measuring a three-dimensional topography of a feature of a pattern of a lithography patterning device and calculating from the measurements wavefront phase information caused by the three-dimensional topography of the pattern.

A method including, for an illumination by radiation of a pattern of a lithographic patterning device, obtaining calculated wavefront phase information caused by three-dimensional topography of the pattern, and based on the wavefront phase information, adjusting a parameter of the illumination and/or adjusting a parameter of the pattern.

A lithographic apparatus comprising a projection system comprising at least one optical component and configured to project a pattern onto a substrate. The lithographic apparatus further comprises a control system arranged to reduce the effects of heating and/or cooling of an optical component in a lithographic process. The control system is configured at least: to select at least one of a plurality of mode shapes to represent a relationship between at least one input in the lithographic process and an aberration resulting from the input and to generate and apply a correction to the lithographic apparatus based on the mode shape.

Methods for calibrating a photolithographic system are disclosed. A cold lens contour for a reticle design and at least one hot lens contour for the reticle design are generated from which a process window is defined. Aberrations induced by a lens manipulator are characterized in a manipulator model and the process window is optimized using the manipulator model. Aberrations are characterized by identifying variations in critical dimensions caused by lens manipulation for a plurality of manipulator settings and by modeling behavior of the manipulator as a relationship between manipulator settings and aberrations. The process window may be optimized by minimizing a cost function for a set of critical locations.