An illumination system has a microLED array 502. The microLED array 502 is imaged or placed very close to a phosphor coated glass disc 504 which upconverts the light from the microLED array into a narrow band emission. The plate has at least two different photoluminescent materials arranged to be illuminated by the microLED array and to thereby emit output light. The different photoluminescent materials have different emission spectral properties of the output light, e.g. different center wavelength and optionally different bandwidth. Illumination of different photoluminescent materials by the illumination sources is selectable, by selective activation of the microLEDs or by movement of the photoluminescent materials relative to the illumination sources, to provide different illumination of the different photoluminescent materials. This provides tunable spectral properties of the output light. Selectively configurable filters 506 are arranged to filter the output light in accordance with the selected illumination of the different photoluminescent materials.

A metrology target includes: a first structure arranged to be created by a first patterning process; and a second structure arranged to be created by a second patterning process, wherein the first structure and/or second structure is not used to create a functional aspect of a device pattern, and wherein the first and second structures together form one or more instances of a unit cell, the unit cell having geometric symmetry at a nominal physical configuration and wherein the unit cell has a feature that causes, at a different physical configuration than the nominal physical configuration due to a relative shift in pattern placement in the first patterning process, the second patterning process and/or another patterning process, an asymmetry in the unit cell.

An imprint apparatus for forming a pattern of an imprint material on a substrate using a mold having a mesa including a pattern region where a pattern and a mark are formed. The apparatus includes an alignment optical system which includes an illumination system configured to illuminate the mark with illumination light and a detecting system configured to detect an image of the mark illuminated by the illumination system. The illumination system includes a limiter configured to limit incidence of the illumination light to a side of the mesa, a ridge line of the mesa, and an outer region of the side.

Metrology targets, production processes and optical systems are provided, which enable metrology of device-like targets. Supplementary structure(s) may be introduced in the target to interact optically with the bottom layer and/or with the top layer of the target and target cells configurations enable deriving measurements of device-characteristic features. For example, supplementary structure(s) may be designed to yield Moiré patterns with one or both layers, and metrology parameters may be derived from these patterns. Device production processes were adapted to enable production of corresponding targets, which may be measured by standard or by provided modified optical systems, configured to enable phase measurements of the Moiré patterns.

A device manufacturing method including: performing a first exposure on a substrate using a first lithographic apparatus to form a first patterned layer including first features; processing the substrate to transfer the first features into the substrate; and performing a second exposure on the substrate using a second lithographic apparatus to form a second patterned layer including second features, wherein: the first lithographic apparatus has first and second control inputs effective to control first and second parameters of the first features at least partly independently; the second lithographic apparatus has a third control input effective to control the first and second parameters of the second features together; and the first exposure is performed with the first and/or second control input set to pre-bias the first and/or second parameter.

Disclosed is a method for obtaining a computationally determined interference electric field describing scattering of radiation by a pair of structures comprising a first structure and a second structure on a substrate. The method comprises determining a first electric field relating to first radiation scattered by the first structure; determining a second electric field relating to second radiation scattered by the second structure; and computationally determining the interference of the first electric field and second electric field, to obtain a computationally determined interference electric field.

Disclosed is target arrangement comprising a first target region having at least a first pitch and at least a second pitch a second target region having at least a third pitch, wherein a portion of the first target region having a second pitch overlaps with a portion of the second target region.

Metrology targets and methods are provided, which comprise at least two overlapping structures configured to be measurable in a mutually exclusive manner at least at two different corresponding optical conditions. The targets may be single cell targets which are measured at different optical conditions which enable independent measurements of the different layers of the target. Accordingly, the targets may be designed to be very small, and be located in-die for providing accurate metrology measured of complex devices.

A method and system for predicting complex electric field images with a parameterized model are described. A latent space representation of a complex electric field image is determined based on dimensional data in a latent space of the parameterized model for a given input to the parameterized model. The given input may be a measured amplitude (e.g., intensity) associated with the complex electric field image. The complex electric field image is predicted based on the latent space representation of the complex electric field image. The predicted complex electric field image includes an amplitude and a phase. The parameterized model comprises encoder-decoder architecture. In some embodiments, determining the latent space representation of the electric field image comprises minimizing a function constrained by a set of electric field images that could be predicted by the parameterized model based on the dimensional data in the latent space and the given input.

Methods and systems are described for generating assessment maps. A method includes receiving a first vector map comprising a first set of vectors each indicating a distortion of a particular location on a substrate and generating a second vector map indicating a change in direction of a magnitude of the distortion of the particular location on the substrate. The method further includes generating a third vector map comprising vectors reflecting reduced noise in distortions across the plurality of locations on the substrate and generating a fourth vector map projecting a direction component of each vector component in the third set of vectors to a radial direction. The method further includes generating a fifth vector map by grouping the vectors of the fourth set of vectors and determining a magnitude associated with each group of vectors.