Growth of boron nitride thin films by tuned substrate RF magnetron sputtering

Abstract

Thin films of boron nitride (BN) were prepared by tuned substrate RF magnetron sputtering from a h-BN target (99.99% purity) using Ar and N2 as processing gases. The films were deposited on c-Si(100) wafers and Corning 7059 glass substrates heated to about 350 °C. The sputter deposition process was carried out at measured pressures between 0.1 and 0.3 Pa with the nitrogen concentration fixed at 65%. The dc potential developed in the target was about − 550V as the substrate bias voltage was varied from +15 V to − 90V through a variable reactance connecting the substrate electrode to ground, which suppresses the need for an external power source. The deposition rate of the films was about 2.3A˚s−1 but increased to 3.3A˚s−1 for the film biased at − 90 V. EPMA analysis indicated near-stoichiometric films, which exhibited a uniform composition in the SIMS depth profiles. FTIR spectra showed two absorption bands at 780 and 1385 cm−1, corresponding to the hexagonal phase of BN, and another absorption band attributed to the c-BN phase for the most negative biased films. A preferred orientation of the h-BN phase was simultaneously deduced from both the FTIR spectra and the XRD patterns. The films were highly transparent in the visible and near-IR region, and presented refractive index values between 1.64 and 1.75.