Metrology method, metrology apparatus and device manufacturing method

Abstract

A pattern is applied to a substrate by a lithographic apparatus as part of a lithographic manufacturing system. Structures are produced with feature sizes less than 10 nm. A target includes one or more gratings with a direction of periodicity. A detector captures one or more diffraction spectra, to implement small angle X-ray scattering metrology. One or more properties, such as linewidth (CD), are calculated from the captured spectra for example by reconstruction. The irradiation direction defines a non-zero polar angle relative to a direction normal to the substrate and defines a non-zero azimuthal angle relative to the direction of periodicity, when projected onto a plane of the substrate. By selecting a suitable azimuthal angle, the diffraction efficiency of the target can be enhanced by a large factor. This allows measurement time to be reduced significantly compared with known techniques.