Influence of sputtering target material on the formation of cubic BN thin films by ion beam enhanced deposition

Abstract

The influence of the sputtering target material on the formation of cubic BN (c-BN) deposited by ion beam enhanced deposition was investigated. Boron or BN films were deposited onto silicon substrates by ion beam sputtering of a pure boron or hexagonal BN (h-BN) sputter-target. An ion beam mixture of argon and/or nitrogen ions was bombarded concurrently onto the growing film. The resulting films were characterized by Fourier transform IR spectroscopy and X-ray photoelectron spectroscopy (XPS). The mass spectra of particles sputtered from the h-BN target were analyzed by secondary ion mass spectrometry (SIMS) using 1–3 keV argon ion beams. Almost single-phase c-BN was deposited using the boron target but, in contrast, c-BN was not formed under any conditions using the h-BN target. The results obtained by XPS and SIMS showed that the h-BN target contained moisture absorbed from the air, and most of the boron atoms were sputtered from the target as compounds of BN, BO or BH when the energy of the sputtering argon ions was less than 2 keV. It is considered that free boron atoms must encounter highly activated nitrogen ions to form c-BN. Nitrogen or other atoms sputtered with boron from the h-BN target seem to interrupt the reaction of boron atoms with the bombarded nitrogen ions to form c-BN.