AVS 45th International Symposium
    Vacuum Metallurgy Division Monday Sessions
       Session VM-MoA

Paper VM-MoA1
Low Temperature Growth of Protective Coatings in an ECR Plasma

Monday, November 2, 1998, 2:00 pm, Room 328

Session: Plasma Assisted Surface Treatments and Coatings
Presenter: T.D. Mantei, University of Cincinnati
Authors: C.-T. Lin, University of Cincinnati
F. Li, University of Cincinnati
T.D. Mantei, University of Cincinnati
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A high density microwave electron cyclotron resonance (ECR) discharge has been used to grow hard, colorless, and transparent silicon dioxide barrier coatings at deposition rates up to 0.7 µm/min and substrate temperatures from 80 to 120°C. The deposition precursors tested were tetraethoxysilane (TEOS), hexamethyldisiloxane (HMDSO), and hexamethylcyclotrisiloxane (HMCTSO). Metal substrates were introduced into the process chamber through a vacuum loadlock and subjected to an in situ three minute argon plasma cleaning cycle. Oxygen was then metered into the chamber through ports located upstream just below the input microwave window, while the precursor reactant gas was introduced downstream. The total gas pressure prior to plasma ignition was 1 to 10 mTorr and the O@sub 2@/precursor flow ratios were varied from 2:1 to 8:1. The substrate temperature, measured with a clamped thermocouple, rose to 80-100°C within a few minutes and then rose slowly during the remainder of the deposition cycle to a final temperature less than 120°C. Final film thicknesses were 3 to 10 µm. Maximum deposition growth rates were 0.25 µm/min for TEOS, 0.65 µm/min for HMDSO, and 0.68 µm/min for HMCTSO, increasing with increasing precursor gas flow, increasing input power, and decreasing O@sub 2@/precursor flow ratio. Fourier transform infrared spectroscopy analysis showed mainly Si-O elemental bonding for all films, with small Si-CH@sub 3@ and SiOH components. Coating compositional analyses performed with X-ray photoelectron spectroscopy showed oxygen-to-silicon ratios of approximately 2:1, but with significant carbon percentages; e.g. the carbon fraction for TEOS films ranged from 29% with an O@sub 2@/precursor flow ratio of 2.5, down to 14% for an 8:1 flow ratio.