Reduced bias growth of pure-phase cubic boron nitride

We report results on an improved growth process for cubic boron nitride (c-BN) films. The films are deposited on a de-biased silicon substrate using ion-assisted sputtering. First, we grow a BN template layer at a bias voltage which maximizes the sp(3) content. After this template layer attains a thickness of similar to 500 Angstrom, corresponding to the coalescence of the mosaiclike grain structure, we find that we can reduce the substrate bias to about 50% of its initial value while sustaining pure phase c-BN growth. The reduction in nitrogen ion energy results in a dramatic increase in the growth rate as well as significantly improved film quality. (C) 1997 American Institute of Physics.