Simultaneous real-time spectroscopic ellipsometry and reflectance for monitoring thin-film preparation.

An expansion of the capabilities of high-speed, multichanneI spectroscopic ellipsometry (SE) is described that involves simultaneous measurement of the reflectance spectrum along with the two spectra in the ellipsometric angles (ψ, Δ). previously, a novel rotating-polarizer spectroscopic ellipsometer has been perfected that employs a photodiode array detector for high-speed acquisition of (ψ, Δ) spectra, designed for real-time studies of thin-film growth. For a polarizer angular rotation frequency of ω[sub 0], the (ψ, Δ) values at a given photon energy are deduced from the 2ω[sub 0] Fourier components of the detector irradiance, normalized by the dc component. A third parameter, the weighted reflectance R[sub A], can be obtained from the dc component and from a calibration based on the known optical properties of the substrate measured prior to film growth, With (ω[sub 0]/2π) = 12.5 Hz, three-parameter data sets, [ψ(hυ), Δ (h υ), R[sub A](h &upsilonl); 1.5 ≤ h υ ≤ 4.5 eV], can be acquired with a time ' resolution as short as 40 ms. Although R[sub A] provides complementary information to (ψ, Δ), it has yet to be exploited in conjunction with real-time SE until this study. A resilient analysis approach, based on mathematical inversion and least-squares fitting of the real-time three-parameter data sets, is designed to yield the film dielectric functions and thicknesses independently at each time during the early stages of thin-film growth. The three-parameter approach has been. applied successfully in studies of amorphous silicon (a-Si:H) thin films PrePared by plasma-enhanced chemical vapor deposition, and aluminum and silver films prepared by physical vapor deposition. For the a-Si:H films, R[sub A](h ν) exhibits deviations as large as ∼3% from that predicted in modeling (ψ, Δ) alone. The deviations result from light scattering by plasma... [ABSTRACT FROM AUTHOR]