Variable angle of incidence spectroscopic autocollimating ellipsometer

Abstract

We present a spectroscopic, autocollimating ellipsometer capable of operating at arbitrary angles of incidence. Linearly polarized light incident on a sample is circularly polarized on reflection, ensuring that the retroreflected beam is orthogonal to the input polarization state. In order to achieve this at arbitrary angles of incidence, a Soleil-Babinet compensator (SBC) is introduced with its fast axis fixed horizontally. Nulling is achieved by varying the SBC delay and the azimuthal angle of the input linear polarization. A single calibration equation at a fixed wavelength and a knowledge of the wavelength dependence of the compensator birefringence enables the delay to be accurately calculated at any wavelength. Single-wavelength, variable angle of incidence measurements made on a thick gold film are in excellent agreement with those obtained with a traditional null ellipsometer. Spectroscopic measurements at a fixed angle of incidence of a silicon dioxide film on a silicon substrate yield thicknesses that are in excellent agreement with independent measurements made with a null ellipsometer and a commercial instrument.

White-light ellipsometer with geometric phase shifter

“…The best-fit film thickness, as obtained by a commercial software package, Thin Film Companion (TFC) [29], was 1000.6 0.1 Å. This is in excellent agreement with a value of 997 3 Å obtained using a single wavelength (λ 632.8 nm), multiple AOI commercial ellipsometer [30] and with previous spectroscopic measurements [31], which yielded 1003 3 Å at the same AOI. Plotted on the same figure for comparison are calculated values of ψ and Δ for the best-fit thickness.…”

Return-path, multiple-principal-angle, internal-reflection ellipsometer for measuring IR optical properties of aqueous solutions

“…Ellipsometry at the principal angle of incidence, at which the differential reflection phase shift Δ ¼ AEπ=2, is attractive because of the high precision associated with the detection of this condition [6][7][8][9] and because a simple instrument that employs the return-path (autocollimation or retroreflection) configuration [10][11][12][13][14][15][16][17] can be used.…”

“…1. (The polarizer transmission-axis azimuth P, measured from the plane of incidence, and angle of incidence ϕ can be determined with a precision of 0:001°using commercially available rotational mounts [17]). As in O'Bryan's original vacuum ellipsometer [10], the polarizer and sample are rotated until the output electrical signal of detector D is extinguished.…”