A projection system model is configured to predict optical aberrations of a projection system based upon a set of projection system characteristics and to determine and output a set of optical element adjustments based upon a merit function. The merit function comprises a set of parameters and corresponding weights. The method comprises receiving an initial merit function and executing an optimization algorithm to determine a second merit function. The optimization algorithm scores different merit functions based upon projection system characteristics of a projection system adjusted according to the output of the projection system model using a merit function having that set of parameters and weights.

The disclosure relates to a microlithography projection exposure system having optical corrective elements configured to modify the imaging characteristics, as well as related systems and component.

An alignment system, method and lithographic apparatus are provided for determining the position of an alignment mark, the alignment system comprising a first system configured to produce two overlapping images of the alignment mark that are rotated by around 180 degrees with respect to one another, and a second system configured to determine the position of the alignment mark from a spatial distribution of an intensity of the two overlapping images.

A microlithographic apparatus comprises an optical wavefront manipulator. The latter includes an optical element and a gas-tight cavity that is partly confined by the optical element or contains it. A gas inlet device directs a gas jet towards the optical element. The location, where the gas jet impinges on the optical element after it has passed through the cavity, is variable in response to a control signal supplied by a control unit. A gas outlet is in fluid connection with the vacuum pump so that, upon operation of the vacuum pump, the pressure within the cavity is less than 10 mbar even if the gas jet passes through the cavity.

A method to form on a substrate a first target comprising a first feature and a second target comprising a second feature, wherein the forming of the targets comprises applying the first feature and the second feature to the substrate by projection of a radiation beam through a production patterning device installed in a lithographic apparatus, the features corresponding to one or more features of the patterning device, and controlling a configuration of the lithographic apparatus to induce an aberration component, such that the first feature is applied to the substrate using a first value of an induced aberration component and the second feature is applied to the substrate using a second, different value of the induced aberration component; measuring a property of the targets; and using the measurements to determine a sensitivity of the property of the targets to changes in value of the induced aberration component.

A lithographic apparatus applies patterns to substrates, the substrates being processed as a plurality of lots. Each lot of substrates receives a particular layer pattern under layer-specific operating conditions. A thermal model is provided for modeling and compensating one or more characteristics of thermal behavior of components within the lithographic apparatus, in response to the varying layer-specific operating conditions associated with a sequence of lots. The thermal model is also used to simulate thermal behavior of the apparatus when processing a given collection of lots in different possible sequences. Based on comparison of the simulated thermal behavior in different sequences of lots, an optimized sequence is determined. Optionally, lot sequencing rules are determined and used to obtain a preferred thermal behavior when processing a collection of lots in the future.

A method of operating a projection exposure tool for microlithography is provided. The projection exposure tool has a projection objective for imaging object structures on a mask into an image plane using electromagnetic radiation, during which imaging the electromagnetic radiation causes a change in optical properties of the projection objective. The method comprises the steps of: providing the layout of the object structures on the mask to be imaged and classifying the object structures according to their type of structure, calculating the change in the optical properties of the projection objective effected during the imaging process on the basis of the classification of the object structures, and using the projection exposure tool for imaging the object structures into the image plane, wherein the imaging behavior of the projection exposure tool is adjusted on the basis of the calculated change of the optical properties in order to at least partly compensate for the change of the optical properties of the projection objective caused by the electromagnetic radiation during the imaging process.

A calibration curve for a wafer comprising a layer on a substrate is determined. The calibration curve represents a local parameter change as a function of a treatment parameter associated with a wafer exposure to a light. The local parameter of the wafer is measured. An overlay error is determined based on the local parameter of the wafer. A treatment map is computed based on the calibration curve to correct the overlay error for the wafer. The treatment map represents the treatment parameter as a function of a location on the wafer.

A projection exposure apparatus (10) for microlithography has a measuring system (50) for measuring an optical element of the projection exposure apparatus. The measuring system (50) includes an irradiation device (54), which is configured to radiate measuring radiation (62) in different directions (64) onto the optical element (20), such that the measuring radiation (62) covers respective optical path lengths (68) within the optical element (20) for the different directions (64) of incidence, a detection device (56), which is configured to measure, for the respective directions (64) of incidence, the respective optical path lengths covered by the measuring radiation (62) in the optical element (20), and an evaluation device, which is configured to determine a spatially resolved distribution of refractive indices in the optical element (20) by computed-tomographic back projection of the respective measured path lengths with respect to the respective directions of incidence.

A structure of interest is irradiated with radiation for example in the x-ray or EUV waveband, and scattered radiation is detected by a detector (306). A processor (308) calculates a property such as linewidth (CD) by simulating interaction of radiation with a structure and comparing the simulated interaction with the detected radiation. A layered structure model (600, 610) is used to represent the structure in a numerical method. The structure model defines for each layer of the structure a homogeneous background permittivity and for at least one layer a non-homogeneous contrast permittivity. The method uses Maxwell's equation in Born approximation, whereby a product of the contrast permittivity and the total field is approximated by a product of the contrast permittivity and the background field. A computation complexity is reduced by several orders of magnitude compared with known methods.