Preparation of Cubic Boron Nitride Films by RF Sputtering

Cubic boron nitride (c-BN) films have been prepared by sputtering of a hexagonal BN sintered target under a negative self-bias voltage applied to Si substrates and a sputtering gas composition of Ar/N2. A c-BN phase was found to be contained only in the films prepared in pure Ar discharge with a negative self-bias above a threshold value. Moreover, the ratio of c-BN to hexagonal boron nitride increased with increasing negative self-bias voltage. The films consisting mainly of the c-BN phase were easily peeled from Si substrates on exposure to air because of their strong compressive stress.