Conditions for the formation of cubic boron nitride films by r.f. magnetron sputtering

Boron nitride films were prepared on Si (100) substrates by r.f. magnetron sputtering from an hBN target with pure argon as working gas. During the deposition, the growing film was ion-bombarded via an r.f. bias at the substrate without additional heating. The deposited films were characterized by Fourier transform infra-red spectroscopy. It was found that the cubic BN phase was formed only within a narrow window of the substrate bias voltage, and after the substrate was heated up to about 300 °C by the ion bombardment. With carefully controlled deposition parameters, a cBN fraction above 90% was achieved. With increasing argon pressure, the cBN forming window of the substrate bias voltage was found to be shifted to higher voltages, whereas the width of this window became broader. The energy distribution of bombarding ions at the substrate has been measured and is discussed with regard to the cBN-forming energy window.