Single sequence phase shifting spectrally resolved interferometry for an in-line thin film thickness measurement using spectral reflectance and phase.

A novel, to the best of our knowledge, thickness measurement scheme based on a phase shifting spectrally resolved interferometry is proposed for a thin film measurement from spectral reflectance and phase in a single sequence. This purpose is realized by introducing a spectral reflectance phase surface (SRPS). The spectral phase, originally existing in the form of an imaginary term, is revealed as a real term with the spectral reflectance due to the proposition of SRPS. Therefore, the reflectance and phase are contained in a single parameter, SRPS, and are measured in a single sequence. The phase shift error compensation is presented to form the accurate SRPS and ensure the performance of the measurement. The thickness of the sample is determined as the measured SRPS, and the theoretical SRPSs are compared by the cross correlation method. The performance of the proposed system is validated by measuring several samples of the SiO2 on a silicon substrate and comparing the results with the commercial ellipsometer.

Single-sequence stable spectroscopic reflectometry using simultaneous measurement of incident light and reflected light: publisher's note.

This publisher's note contains corrections to Appl. Opt.60, 8915 (2021).APOPAI0003-693510.1364/AO.435321.

Single-sequence stable spectroscopic reflectometry using simultaneous measurement of incident light and reflected light.

We proposed a new scheme of spectroscopic reflectometry (SR) that improves the stability with respect to the intensity variations of the incident light and simplifies the measurement procedure. The proposed method enables this by simultaneously measuring the incident light and the reflected light. Using the multi-order retarder, we modulate the incident light intensity into a high-frequency signal at the spectral domain. Even though the spectrometer measures the sum of reflected light and modulated incident light, each signal can be separately obtained using the Fourier transform. The proposed method is verified through the measurement of SiO2 thin film on the Si substrate with various incident light intensities.

Coaxial spectroscopic imaging ellipsometry for volumetric thickness measurement.

We propose spectroscopic imaging ellipsometry that can measure spectral ellipsometric signals in the entire field of view simultaneously without areal scanning or operation of polarization devices. The proposed imaging ellipsometry is configured in a coaxial optical structure so that the high magnification objective lens is applicable and the spatial resolution is highly increased. Without the operation of polarization components and to efficiently obtain the spectral data in the object plane, the ellipsometric parameters are encoded into the high frequency in the spectral domain and are measured by an imaging Michelson interferometer. The volumetric thickness measurement by the proposed method was verified by comparing the thickness results of the SiO2/Si sample that has four different thicknesses with commercial ellipsometer results.

Simple method for volumetric thickness measurement using a color camera.

A simple volumetric thickness measurement method for in-line high-speed inspection is proposed. With a color camera alone, spectrally resolved reflectance in a spatial domain is obtained: a Bayer filter spectrally resolves the reflected signal, and a CMOS sensor acquires three multi-spectral reflectances from RGB data at a single shot. To determine an accurate thickness, a modified reflectance is derived to convert a conventional spectral reflectance throughout a wavelength domain into an adequate form in an RGB domain by considering the characteristics of wide-band multi-spectral acquisition. The proposed method is validated by the measurement of a uniformly deposited SiO2 film and a tapered SiNx film.