GROWTH OF BORON-NITRIDE THIN-FILMS BY TUNED SUBSTRATE RF MAGNETRON SPUTTERING

Thin films of boron nitride (BN) were prepared by tuned substrate RF m agnetron sputtering from a h-BN target (99.99% purity) using Ar and N- 2, as processing gases. The films were deposited on c-Si(100) wafers a nd Coming 7059 glass substrates heated to about 350 degrees C. The spu tter deposition process was carried out at measured pressures between 0.1 and 0.3 Pa with the nitrogen concentration fixed at 65%. The de po tential developed in the target was about -550 V as the substrate bias voltage was varied from +15 V to -90 V through a variable reactance c onnecting the substrate electrode to ground, which suppresses the need for an external power source. The deposition rate of the films was ab out 2.3 Angstrom s(-1) but increased to 3.3 Angstrom s(-1) for the fil m 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), correspon ding to the hexagonal phase of BN, and another absorption band attribu ted 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 valu es between 1.64 and 1.75.