Co-axial spectroscopic snap-shot ellipsometry for real-time thickness measurements with a small spot size

Spectroscopic snap-shot ellipsometry of co-axial structure is proposed to solve the large spot size and long measurement time issues of the conventional ellipsometer. By modulating the spectroscopic ellipsometry signal into high-frequency at the spectral domain and measuring the spectrum at the point of the back focal plane, the ellipsometry parameters(Δ, ψ) were measured in real-time with small spot size. Detailed analysis, calibration, and optimization process for the proposed methods are presented. The accuracy and precision of the proposed method were confirmed by comparing the thickness measurement result of SiO₂/Si thin-film samples with a commercial ellipsometer.