Stoichiometric SiO2 thin films deposited by reactive sputtering

We report a study of experimental possibilities to produce high purity stoichiometric SiO2 thin films by reactive ion beam sputtering. The films were deposited in a UHV chamber, 4 × 10−9 mbar, using a high purity silicon target and 1 keV Ar+ ions for sputtering. The ion beam current was varied from 1.67 to 6.85 mA, at a constant argon partial pressure of 1 × 10−3 mbar. Different values of the oxygen partial pressure (5 × 10−6–1 × 10−3 mbar) were applied for reactive deposition. The substrates were held at room temperature or at 550 °C, and the films were deposited to 12.5–150 nm, at 0.0018–0.035 nm s−1. Structural characterization was performed by Rutherford backscattering spectrometry (RBS), electron microprobe, X-ray diffraction (XRD) and Raman spectroscopy. The results show that reactive ion beam sputtering can be efficient for deposition of high quality silica films at 550 °C, oxygen partial pressure of 2 × 10−4 mbar and ion beam current on the target from 5 to 5.5 mA, or at a lower deposition rate, ion beam current of 1.67 mA and oxygen partial pressure of 6 × 10−5 mbar. One aspect of these investigations was to study consumption of oxygen from the gas cylinder, which was found to be lower for higher deposition rates.