Remote plasma‐enhanced chemical vapor deposition of SiO 2 using a radio‐frequency (rf) Ar/ N 2 O plasma and downstream‐injected SiH 4 was investigated. The deposition rate at 20 W rf power was measured as a function of pressure, temperature, and SiH 4 flow rate. The SiO 2 deposition rate at 300°C and 300 mTorr depends linearly on the SiH 4 flow rate. The deposition rate is independent of N 2 O flow rate for N 2 O / SiH 4 ratios much greater than 1, consistent with oxygen saturation of the growth surface. The deposition rate increases linearly with pressure up to 400 mTorr. A plateau in the deposition rate is observed above 400 mTorr, and is ascribed to the onset of parasitic gas‐phase reactions leading to particle formation. Negative apparent activation energies are observed at pressures ⩽400 mTorr, suggesting that adsorption of Si‐bearing species is the rate‐limiting step in SiO 2 deposition. The deposition chemistry was probed using real‐time quadrupole mass spectrometry (QMS) and optical emission spectroscopy (OES). The H 2 + and H 2 O + QMS signal intensities increase monotonically with SiH 4 flow rate; approximately 0.67 moles of H 2 and 1.33 moles of H 2 O are produced per mole of SiH 4 consumed. OES evidences the presence of Ar metastables, N 2 metastables, excited NO molecules, and atomic O in the plasma. Fourier transform infrared spectroscopy of thick SiO 2 films demonstrated that Si‐H and Si‐OH groups are present at very low concentrations (<1 atom %). Single‐wavelength ellipsometry indicated that films deposited under typical O‐rich conditions have an average refractive index of 1.464.
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Courtney et al. (1998) studied this question.