A lithography system includes an illumination source including two illumination poles separated along a first direction and symmetrically distributed around an optical axis, a pattern mask to receive illumination from the illumination source, and a set of projection optics to generate an image corresponding to the pattern mask onto a sample. The pattern mask includes a metrology target pattern mask and device pattern mask elements. The device pattern mask elements are distributed along the first direction with a device separation distance. The metrology target pattern mask includes a set of metrology target pattern mask elements having a diffraction pattern corresponding to that of the device pattern mask elements. A metrology target generated on the sample associated with the metrology target pattern mask is characterizable along a second direction and has printing characteristics corresponding to those of device pattern elements generated on the sample associated with the device pattern mask elements.

A metrology target for use in measuring misregistration between layers of a semiconductor device including a first target structure placed on a first layer of a semiconductor device, the first target structure including a first plurality of unitary elements respectively located in at least four regions of the first target structure, the first plurality of elements being rotationally symmetric with respect to a first center of symmetry and at least a second target structure placed on at least a second layer of the semiconductor device, the second target structure including a second plurality of elements respectively located in at least four regions of the second target structure, the second plurality of elements being rotationally symmetric with respect to a second center of symmetry, the second center of symmetry being designed to be axially aligned with the first center of symmetry and corresponding ones of the second plurality of elements being located adjacent corresponding ones of the first plurality of elements in the at least four regions in a non-surrounding arrangement, when the first and second layers are placed one on top of another.

Disclosed is a substrate and associated patterning device. The substrate comprises at least one target arrangement suitable for metrology of a lithographic process, the target arrangement comprising at least one pair of similar target regions which are arranged such that the target arrangement is, or at least the target regions for measurement in a single direction together are, centrosymmetric. A metrology method is also disclosed for measuring the substrate. A metrology method is also disclosed comprising which comprises measuring such a target arrangement and determining a value for a parameter of interest from the scattered radiation, while correcting for distortion of the metrology apparatus used.

In various embodiments, an exposure mask may include a carrier, a first exposure structure in a first structure plane of the carrier, and a second exposure structure in a second structure plane of the carrier. The two structure planes differ from one another.

A structure of interest (T) is irradiated with radiation for example in the x-ray or EUV waveband, and scattered radiation is detected by a detector (19, 274, 908, 1012). A processor (PU) calculates a property such as linewidth (CD) or overlay (OV), for example by simulating (S16) interaction of radiation with a structure and comparing (S17) the simulated interaction with the detected radiation. The method is modified (S14a, S15a, S19a) to take account of changes in the structure which are caused by the inspection radiation. These changes may be for example shrinkage of the material, or changes in its optical characteristics. The changes may be caused by inspection radiation in the current observation or in a previous observation.

A diffraction measurement target that has at least a first sub-target and at least a second sub-target, and wherein (1) the first and second sub-targets each include a pair of periodic structures and the first sub-target has a different design than the second sub-target, the different design including the first sub-target periodic structures having a different pitch, feature width, space width, and/or segmentation than the second sub-target periodic structure or (2) the first and second sub-targets respectively include a first and second periodic structure in a first layer, and a third periodic structure is located at least partly underneath the first periodic structure in a second layer under the first layer and there being no periodic structure underneath the second periodic structure in the second layer, and a fourth periodic structure is located at least partly underneath the second periodic structure in a third layer under the second layer.

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 method of characterizing a lithographic mask type uses a mask having thereon test pattern units of linear features at different orientations. The mask is exposed, rotated by angle, exposed again, rotated by a further angle, exposed, etc. The printed features are measured to determine one or more characteristics of the mask. The method can be used to model shadowing effects of a EUV mask with a thick absorber illuminated at an angle.

Apparatuses and methods of overlay measurement are disclosed. An example apparatus includes first and second layers. The first layer includes a first alignment pattern that includes a first line extending in a first direction. The first line includes first, second and third segments. The second layer above the first layer includes a second alignment pattern including: a second line extending in the first direction above the first segment and having a first offset from the first segment in a second direction perpendicular to the first direction; a third line extending in the first direction above the second segment and having a second offset from the second segment in the second direction; and a fourth line extending in the first direction above the third segment and having a third offset from the third segment in the second direction. The first, second and third offsets are different from one another.

Disclosed is a method of measuring a target, associated substrate comprising a target and computer program. The target comprises overlapping first and second periodic structures. The method comprising illuminating the target with measurement radiation and detecting the resultant scattered radiation. The pitch of the second periodic structure is such, relative to a wavelength of the measurement radiation and its angle of incidence on the target, that there is no propagative non-zeroth diffraction at the second periodic structure resultant from said measurement radiation being initially incident on said second periodic structure. There may be propagative non-zeroth diffraction at the second periodic structure which comprises further diffraction of one or more non-zero diffraction orders resultant from diffraction by the first periodic structure. Alternatively, the detected scattered radiation may comprise non-zero diffraction orders obtained from diffraction at said the periodic structure which have been disturbed in the near field by the second periodic structure.