Inspection Apparatus, Inspection Method and Manufacturing Method

A product structure (407, 330′) is formed with defects (360-366). A spot (S) of EUV radiation which is at least partially coherent is provided on the product structure (604) to capture at least one diffraction pattern (606) formed by the radiation after scattering by the product structure. Reference data (612) describes a nominal product structure. At least one synthetic image (616) of the product structure is calculated from the captured image data. Data from the synthetic image is compared with the reference data to identify defects (660-666) in the product structure. In one embodiment, a plurality of diffraction patterns are obtained using a series overlapping spots (S(1)-S(N)), and the synthetic image is calculated using the diffraction patterns and knowledge of the relative displacement. The EUV radiation may have wavelengths in the range 5 to 50 nm, close to dimensions of the structures of interest.