Towards Grating Reconstruction in Coherent Fourier Scatterometry

Incoherent Optical Scatterometry (IOS) is a well-established technique in electronic industries for semiconductor metrology. Using this technique one is able to retrieve the properties of the scatterer using the diffracted field. In conventional optical scatterometry, light from an incoherent source is incident on the scatterer (grating) and after the interaction, the angular spectrum is recorded by a detector in the Fourier plane (called far field intensity data). The diffracted far field contains the information about the material composition and the geometrical profile (shape parameters) of the grating. Any change in either the material composition or the geometrical profile of the grating will result in a nonlinear change in the far field data. The technique has several advantages: it is fast, efficient, easy to implement and free from diffraction limit.