A method of measuring a parameter of interest relating to a structure formed by a process on a substrate, and associated apparatuses. The method includes measuring the structure with measurement radiation including a first illumination acquisition setting (determining one or more selected from: a wavelength, a polarization or an incident angle of the measurement radiation) to obtain a first measurement value for the structure. The method further includes estimating, by applying a correction model to the first measurement value, at least a second measurement value for the structure corresponding to measurement of the structure with a second illumination acquisition setting different from the first illumination acquisition setting.

A method is disclosed that includes splitting a beam of radiation into a first part of the beam having a first polarization and a second part of the beam having a second polarization, forming a first beam with a first polarization distribution between the first polarization and the second polarization and/or a first intensity distribution by modulating the first part of the beam, forming a second beam with a second polarization distribution between the first polarization and the second polarization and/or a second intensity distribution by modulating the second part of the beam, and combining at least a portion of the first beam having the second polarization and at least a portion of the second beam having the first polarization.

The invention relates to a method and a device for characterizing a mask for microlithography. In a method according to the invention, structures of a mask intended for use in a lithography process in a microlithographic projection exposure apparatus are illuminated by an illumination optical unit, wherein the mask is imaged onto a detector unit by an imaging optical unit, wherein image data recorded by the detector unit are evaluated in an evaluation unit. In this case, for emulating an illumination setting predefined for the lithography process in the microlithographic projection exposure apparatus, the imaging of the mask onto the detector unit is carried out in a plurality of individual imagings which differ from one another with regard to the illumination setting set in the illumination optical unit or the polarization-influencing effect set in the imaging optical unit.

A metrology apparatus (302) includes a higher harmonic generation (HHG) radiation source for generating (310) EUV radiation. Operation of the HHG source is monitored using a wavefront sensor (420) which comprises an aperture array (424, 702) and an image sensor (426). A grating (706) disperses the radiation passing through each aperture so that the image detector captures positions and intensities of higher diffraction orders for different spectral components and different locations across the beam. In this way, the wavefront sensor can be arranged to measure a wavefront tilt for multiple harmonics at each location in said array. In one embodiment, the apertures are divided into two subsets (A) and (B), the gratings (706) of each subset having a different direction of dispersion. The spectrally resolved wavefront information (430) is used in feedback control (432) to stabilize operation of the HGG source, and/or to improve accuracy of metrology results.

A method for determining a characteristic of a feature in an object, the feature being disposed below a surface of the object is disclosed. The surface of the object is irradiated with a pulsed pump radiation beam so as to produce an acoustic wave in the object. The surface of the object is then irradiated with a measurement radiation beam. A portion of the measurement radiation beam scattered from the surface is received and a characteristic of the feature in the object is determined from at least a portion of the measurement radiation beam scattered from the surface within a measurement time period. A temporal intensity distribution of the pulsed pump radiation beam is selected such that in the measurement time period a signal to background ratio is greater than a signal to background ratio achieved using a single pulse of the pulsed pump radiation beam. The signal to background ratio is a ratio of: (a) signals generated at the surface by reflections of acoustic waves from the feature to (b) background signals generated at the surface by reflections of acoustic waves which have not reflected from the feature.

A light irradiation method includes splitting light from a coherent light source, which outputs the light at a wavelength equal to or less than 300 nm, into a plurality of branch beams. A wavefront of the light is shaped before splitting the light. The light irradiation method also includes causing the branch beams to intersect at an interference angle equal to or less than 20 to generate interfered light, and irradiating a substrate with the interfered light while continuously conveying the substrate relative to the interfered light.

Correction information is acquired for compensating for a measurement error of a second encoder system that occurs due to a displacement between four sections of a scale member of the second encoder system, based on measurement information of the second encoder system obtained in a fifth area in which four heads of the second encoder system that are provided on a second stage, which holds a substrate, respectively face the four sections of the scale member.

Methods and apparatus for determining an intensity profile of a radiation beam. The method comprises providing a diffraction structure, causing relative movement of the diffraction structure relative to the radiation beam from a first position wherein the radiation beam does not irradiate the diffraction structure to a second position wherein the radiation beam irradiates the diffraction structure, measuring, with a radiation detector, diffracted radiation signals produced from diffraction of the radiation beam by the diffraction structure as the diffraction structure transitions from the first position to the second position or vice versa, and determining the intensity profile of the radiation beam based on the measured diffracted radiation signals.

An inspection apparatus (140) measures asymmetry or other property of target structures (T) formed by a lithographic process on a substrate. For a given set of illumination conditions, accuracy of said measurement is influenced strongly by process variations across the substrate and/or between substrates. The apparatus is arranged to collect radiation scattered by a plurality of structures under two or more variants of said illumination conditions (p1, p1, p1+; 1, 1, 1+). A processing system (PU) is arranged to derive the measurement of said property using radiation collected under a different selection or combination of said variants for different ones of said structures. The variants may be for example in wavelength, or in angular distribution, or in any characteristic of the illumination conditions. Selection and/or combination of variants is made with reference to a signal quality (302, Q, A) observed in the different variants.

An exposure apparatus includes a stage on which a substrate is placed, a plurality of light irradiation units configured to emit light independently of each other to different positions in a right and left direction on a surface of the substrate, so as to form a strip-like irradiation area extending from one end of the surface of the substrate to the other end of the substrate, a stage moving mechanism configured to move the stage in a back and forth direction relative to the irradiation area, such that the whole surface of the substrate is exposed, and a light receiving unit configured move in the irradiation area between one end and the other end of the irradiation area in order to detect an illuminance distribution of the irradiation area in a longitudinal direction of the irradiation area.