Patent ID: 8692994

Claim:
A method comprising: providing a radiation beam with linear polarization; reflecting the linearly polarized radiation beam off a grating on a substrate at a range of incident and azimuth angles; introducing a phase shift, by a phase shifter, to the linearly polarized radiation beam thereby altering its polarization to elliptical; splitting, by a beam splitter, the reflected radiation beam into first and second orthogonally polarized sub-beams; adjusting at least one of the linearly polarized radiation beam, the grating on the substrate, the phase shifter, and the beam splitter to enable sensitivity to multiple polarization angles and sensitivity to detection of at least one of critical dimension, sidewall angle, and thickness; shifting a phase of the first sub-beam by a fixed amount with respect to the second sub-beam; and simultaneously detecting, by a detector, an angle-resolved spectrum of both sub-beams; wherein the grating and the initial linear polarization of the radiation beam are angled non-orthogonally relative to each other.