An optical measurement system for evaluating a sample has a motor-driven rotating
mechanism coupled to an azimuthally rotatable measurement head, allowing the optics
to rotate with respect to the sample. A polarimetric scatterometer, having optics
directing a polarized illumination beam at non-normal incidence onto a periodic
structure on a sample, can measure optical properties of the periodic structure.
An E-O modulator in the illumination path can modulate the polarization. The head
optics collect light reflected from the periodic structure and feed that light
to a spectrometer for measurement. A beamsplitter in the collection path can ensure
both S and P polarization from the sample are separately measured. The measurement
head can be mounted for rotation of the plane of incidence to different azimuthal
directions relative to the periodic structures. The instrument can be integrated
within a wafer process tool in which wafers may be provided at arbitrary orientation.
