Photoelastic modulated imaging ellipsometry by stroboscopic illumination technique

A novel stroboscopic illumination technique is applied in a photoelastic modulated (PEM) ellipsometry to conquer the slow imaging processing of charge-coupled device camera system and form a fast imaging ellipsometry. The synchronized ultrastable short pulse is used to freeze the intensity variation of the PEM modulated signal. The temporal phase is calibrated with respect to the time reference of PEM. The laser diode is modulated by a programable pulse generator for triggering four short pulses at their specific temporal phase angle. The two-dimensional (2D) ellipsometric parameters can be deduced from those recorded four images. Therefore, the 2D thickness profile of a patterned sample can be measured; a static patterned SiO2 thin film on silicon substrate and the drainage behavior of matching oil on silicon wafer were studied by this imaging ellipsometry.