Imaging ellipsometry is developed in the dual-rotation mode of a polarizer and an analyzer. In this system, the polarizer and analyzer are rotated by a stepping motor at 1:1 ratio and the offset between the azimuths of both elements is kept constant. For data reduction, a two-dimensional array detector collects multiple intensity images during rotation and waveform analysis is performed for each pixel. This system generates second and fourth harmonics in intensity waveform and {Δ, Ψ} images are deduced from the amplitudes of these harmonics without considering their phases, which leads to calibration-free imaging ellipsometry. This system works well with an offset between two elements but it becomes less susceptible to an offset-setting error with a smaller offset. Besides the ease of operation, this system is simple to construct as no complicated control mechanism is required for each component.

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We applied spectroscopic ellipsometry for possible determination of the size of contact holes. We fabricated contact hole patterns in two dimensional array to increase sensitivity and the size of contact hole varied from 80 to 150 nm. Variation of hole-diameter in few nm was distinguishable by comparing the features in ellipsometry parameter ∆, Ψ or the degree of polarization spectra. These features could be used to estimate the size of contact holes once they were calibrated by other techniques. When the photoresist film with dense contact hole pattern was regarded as a uniaxial material, the ellipsometry spectra could be analyzed with anisotropic optical model. In the process, the average size of contact hole could be estimated from the anisotropy of the film.