Cubic Boron Nitride Film Synthesis by Reactive Sputtering of Pure Boron Target in Electron Cyclotron Resonance Plasmas

Cubic boron nitride (c-BN) thin films are synthesized by reactive sputtering. Pure boron is used as the sputtering target, which is dc-biassed in an Ar/N 2 electron cyclotron resonance plasma. Substrates are rf-biased with a frequency of 13.56 MHz. BN films with a dominant cubic phase are obtained in the case of a high ion-to-boron flux ratio of 12 at the substrate self-bias higher than -175 V; the transferred momentum per atom is about 1260 (eV amu) 1/2 , which is larger than the value predicted using the momentum transfer model for c-BN synthesis by a factor of 4. An intermediate layer between the c-BN layer and the substrate improves the adhesion of the c-BN layer and prevent a exfoliation. This intermediate layer is deposited under an Ar/N 2 gas mixing ratio of 9 without rf bias.