Using a fast dual-wavelength imaging ellipsometric system to measure the flow thickness profile of an oil thin film

摘要

Highlights • A fast dual-wavelength imaging ellipsometric system was proposed. • An equivalent phase retardation technique was employed in the system. • Retardation dispersion of the modulator can be compensated. • Dual-wavelength measurement can be achieved within several seconds. • Dynamic oil thickness profile on silicon wafer are demonstrated. Abstract Dual-wavelength light sources with stroboscopic illumination technique were applied in a process of photoelastic modulated ellipsometry to retrieve two-dimensional ellipsometric parameters of thin films on a silicon substrate. Two laser diodes were alternately switched on and modulated by a programmable pulse generator to generate four short pulses at specific temporal phase angles in a modulation cycle, and short pulses were used to freeze the intensity variation of the PEM modulated signal that allows ellipsometric images to be captured by a charge-coupled device. Although the phase retardation of a photoelastic modulator is related to the light wavelength, we employed an equivalent phase retardation technique to avoid any setting from the photoelastic modulator. As a result, the ellipsometric parameters of different wavelengths may be rapidly obtained using this dual-wavelength ellipsometric system every 4s. Both static and dynamic experiments are demonstrated in this work.