AVS 46th International Symposium
    Thin Films Division Tuesday Sessions
       Session TF-TuA

Paper TF-TuA2
Microstructural Control of Thin Silicon Films Grown by Reactive Magnetron Sputtering Utilizing Low Energy Ion Bombardment

Tuesday, October 26, 1999, 2:20 pm, Room 615

Session: Fundamentals of Si and Dielectric PVD
Presenter: J. Gerbi, University of Illinois, Urbana-Champaign
Authors: J. Gerbi, University of Illinois, Urbana-Champaign
J.R. Abelson, University of Illinois, Urbana-Champaign
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We use spectroscopic ellipsometry, Raman scattering, TEM, SIMS, and photoluminescence to analyze the optical properties and microstructure of hydrogenated or deuterated Si thin films of various crystallinities. Bulk mc-Si films are of current interest for solar cell, hybrid solar cell, and thin film transistor applications; low temperature deposition enables the use of plastic substrates. We have previously demonstrated that RMS can deposit mc-Si films directly on glass with no amorphous boundary layer,@footnote1@ and that substituting D2 for H2 in the growth process enhances crystallinity.@footnote2@ In this work, we deposit 0.5 micron thick hydrogenated or deuterated mc-Si films on glass substrates by RMS of a Si target using 1.6 mT Ar plus H2 or D2 at partial pressures from 0 mT (producing amorphous films) to 5.5 mT (producing fully microcrystalline films) at substrate temperatures of 120 and 230 C. In our system, the ion flux and energy are decoupled parameters. The ion flux is controlled by the application of a cylindrical magnetic field created by external coils. This field directs a weak plasma toward or away from the substrate, controlling the ion flux such that the ratio of arriving ions to depositing Si atoms can be varied from < 1 to > 30. The ion energy is also externally controlled by biasing the substrate. We find marked differences in microstructure using high ions fluxes at energies <~ 30 eV, and we will report both the microstructural and optical properties of the films. We also show that biasing of the substrate to produce ion energies >= 50 eV (as often done in conventional diode sputtering systems at higher pressures) produces damage which degrades the mc-Si microstructure. @FootnoteText@ @footnote 1@Y. H. Yang and John R. Abelson, Appl. Phys. Lett. 67, 3623 (1995). @footnote 2@ J. E. Gerbi and John R. Abelson, "Enhanced Crystallinity of Microcrystalline Silicon using Deuterium in Low Temperature Reactive Magnetron Sputter Deposition," MRS Proc. 507, 429 (1998).