We demonstrate a method to obtain within an arbitrary numerical aperture (NA) the entire scattering matrix of a scatterer by using focused beam coherent Fourier scatterometry. The far-field intensities of all scattered angles within the NA of the optical system are obtained in one shot. The corresponding phases of the field are obtained by an interferometric configuration. This method enables the retrieval of the maximum available information about the scatterer from scattered far-field data contained in the given NA of the system.

Optical scatterometry is the state of art optical inspection technique for quality control in lithographic process. As such, any boost in its performance carries very relevant potential in semiconductor industry. Recently we have shown that coherent Fourier scatterometry (CFS) can lead to a notably improved sensitivity in the reconstruction of the geometry of printed gratings. In this work, we report on implementation of a CFS instrument, which confirms the predicted performances. The system, although currently operating at a relatively low numerical aperture (NA = 0.4) and long wavelength (633 nm) allows already the reconstruction of the grating parameters with nanometer accuracy, which is comparable to that of AFM and SEM measurements on the same sample, used as reference measurements. Additionally, 1 nm accuracy in lateral positioning has been demonstrated, corresponding to 0.08% of the pitch of the grating used in the actual experiment.

Reflection of light measured in a polarimetric, scatterometric and spectroscopic way allows the measurement of structures in a broad size range from large (meter) scales like photovoltaic panels down to small (nanometer) scales like nanocrystals. Optical metrology continues to be improved to measure those materials with increasing sensitivity and accuracy, typically in a form of thin films on high quality substrates. This review provides an overview of some recently developed or improved methods, e.g. divergent light source ellipsometry for the mapping of large surfaces for photovoltaic applications, Fourier scatterometry for the measurement of periodic structures with sizes comparable to the wavelength of illumination, as well as spectroscopy around the band gap photon energies to characterize nanostructures - without attempting completeness.