Importance

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Abstract

An inspection apparatus is provided for measuring properties of a non-periodic product structure (500′). A radiation source (402) and an image detector (408) provide a spot (S) of radiation on the product structure. The radiation is spatially coherent and has a wavelength less than 50 nm, for example in the range 12-16 nm or 1-2 nm. The image detector is arranged to capture at least one diffraction pattern (606) formed by said radiation after scattering by the product structure. A processor receives the captured pattern and also reference data (612) describing assumed structural features of the product structure. The process uses coherent diffraction imaging (614) to calculate a 3-D image of the structure using the captured diffraction pattern(s) and the reference data. The coherent diffraction imaging may be for example ankylography or ptychography. The calculated image deviates from the nominal structure, and reveals properties such as CD, overlay.

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First Claim