Angle-resolving spectral ellipsometry using structured light for direct measurement of ellipsometric parameters

Abstract

We propose a compact angle-resolving spectral ellipsometry. Using the structured light generated from a digital micro-mirror device (DMD), what we believe to be a novel pattern is illuminated to the back focal plane of the high numerical aperture (NA) objective lens. As a result, ellipsometric parameters with fine resolution of both the wavelength and incidence angle domain can be directly measured. The incidence angle can be resolved by resolution under 1° ranging from 35° to 59° by the radius of the projected images. A spectrometer as a detector enables acquisition by the resolution of 0.7 nm from 410 to 700 nm, and the fiber reduces measurement spot size to a single micrometer. Additionally, the measurement process does not require any rotating optical components or moving parts, needing only digital modification of the projected image. This simplifies the sequences and reduces the measurement time. The 2D (angle of incidence and spectral domain) ellipsometric parameter plane measured by the proposed method was used to measure the thickness of various samples. The measurement result was verified in comparison with a commercial ellipsometer. The accuracy and precision of the result show that the proposed method is capable of precise measurement of thin films.