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Title: Low temperature magnetron sputter deposition of polycrystalline silicon thin films using high flux ion bombardment

Abstract

We demonstrate that the microstructure of polycrystalline silicon thin films depends strongly on the flux of low energy ions that bombard the growth surface during magnetron sputter deposition. The deposition system is equipped with external electromagnetic coils which, through the unbalanced magnetron effect, provide direct control of the ion flux independent of the ion energy. We report the influence of low energy (<27 eV) Ar{sup +} on the low temperature (<450 degree sign C) growth of polycrystalline silicon thin films onto amorphous substrates. We use spectroscopic ellipsometry, Raman scattering, x-ray diffraction, and cross sectional transmission electron microscopy to analyze the film microstructure. We demonstrate that increasing the flux ratio of Ar{sup +} ions to silicon neutrals (J{sup +}/J{sup 0}) during growth by an order of magnitude (from 3 to 30) enables the direct nucleation of polycrystalline Si on glass and SiO{sub 2} coated Si at temperatures below 400 degree sign C. We discuss possible mechanisms for this enhancement of crystalline microstructure, including the roles of enhanced adatom mobility and the formation of shallow, mobile defects.

Authors:
;  [1]
  1. Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W. Green Street, Urbana, Illinois 61801 (United States)
Publication Date:
OSTI Identifier:
20982754
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 101; Journal Issue: 6; Other Information: DOI: 10.1063/1.2710301; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ARGON IONS; CRYSTAL DEFECTS; CRYSTAL GROWTH; DEPOSITION; ELLIPSOMETRY; EV RANGE 10-100; ION BEAMS; MICROSTRUCTURE; NUCLEATION; POLYCRYSTALS; RAMAN EFFECT; RAMAN SPECTRA; SILICON; SILICON OXIDES; SPUTTERING; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0400-1000 K; THIN FILMS; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION

Citation Formats

Gerbi, Jennifer E., and Abelson, John R. Low temperature magnetron sputter deposition of polycrystalline silicon thin films using high flux ion bombardment. United States: N. p., 2007. Web. doi:10.1063/1.2710301.
Gerbi, Jennifer E., & Abelson, John R. Low temperature magnetron sputter deposition of polycrystalline silicon thin films using high flux ion bombardment. United States. doi:10.1063/1.2710301.
Gerbi, Jennifer E., and Abelson, John R. Thu . "Low temperature magnetron sputter deposition of polycrystalline silicon thin films using high flux ion bombardment". United States. doi:10.1063/1.2710301.
@article{osti_20982754,
title = {Low temperature magnetron sputter deposition of polycrystalline silicon thin films using high flux ion bombardment},
author = {Gerbi, Jennifer E. and Abelson, John R.},
abstractNote = {We demonstrate that the microstructure of polycrystalline silicon thin films depends strongly on the flux of low energy ions that bombard the growth surface during magnetron sputter deposition. The deposition system is equipped with external electromagnetic coils which, through the unbalanced magnetron effect, provide direct control of the ion flux independent of the ion energy. We report the influence of low energy (<27 eV) Ar{sup +} on the low temperature (<450 degree sign C) growth of polycrystalline silicon thin films onto amorphous substrates. We use spectroscopic ellipsometry, Raman scattering, x-ray diffraction, and cross sectional transmission electron microscopy to analyze the film microstructure. We demonstrate that increasing the flux ratio of Ar{sup +} ions to silicon neutrals (J{sup +}/J{sup 0}) during growth by an order of magnitude (from 3 to 30) enables the direct nucleation of polycrystalline Si on glass and SiO{sub 2} coated Si at temperatures below 400 degree sign C. We discuss possible mechanisms for this enhancement of crystalline microstructure, including the roles of enhanced adatom mobility and the formation of shallow, mobile defects.},
doi = {10.1063/1.2710301},
journal = {Journal of Applied Physics},
number = 6,
volume = 101,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • Aluminum-doped zinc oxide films were deposited by dc and rf magnetron sputtering from ZnO(98%)Al{sub 2}O{sub 3}(2%) target at room temperature on silicon and glass substrates under a variety of process conditions with the goal of attaining the highest transmittance and lowest resistivity for photovoltaic applications. The magnetron power and pressure were varied. For many dielectric deposition systems, added oxygen is necessary to achieve the appropriate stoichiometry. The effect of oxygen on film properties was then studied by varying the oxygen partial pressure from 1.5x10{sup -5} to 4.0x10{sup -5} T at a constant Ar pressure, with the result that any addedmore » oxygen was deleterious. Films deposited under power, pressure, and low-oxygen conditions were then characterized for electrical and optical properties. Following this, the dc and rf sputtered films were annealed at up to 400 deg. C seconds using rapid thermal annealing (RTA), and the influence of annealing on resistivity, transmittance, band gap, as well as grain growth and stress was studied. The effect of RTA was immediate and quite significant on dc films while the effect on rf films was not as profound. As-deposited rf films had a higher average transmittance (87%) and lower resistivity (5.5x10{sup -4} {Omega} cm) compared to as-deposited dc films (84.2% and 8.9x10{sup -4} {Omega} cm). On the other hand, after RTA at 400 deg. C for 60 s, dc films exhibited better average transmittance (92.3%) and resistivity (2.9x10{sup -4} {Omega} cm) than rf films (90.7% and 4.0x10{sup -4} {Omega} cm). The band gap of dc films increased from 3.55 to 3.80 eV while that of rf films increased from 3.76 to 3.85 eV. Finally, dc and rf films were textured in 0.1% HCl and compared to U-type Asahi glass for resistivity and transmittance.« less
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