Effect of deposition temperature on cubic boron nitride thin film deposited by unbalanced magnetron sputtering method with a nanocrystalline diamond buffer layer

Cubic boron nitride (c-BN) films were deposited by the unbalanced magnetron sputtering method. A Si substrates coated with a nanocrystalline diamond (NCD) was used as a substrate. The deposition temperature was varied systematically from room temperature to 800 C. A boron nitride target was used which was connected to a radio frequency power supply at 400 W. High frequency power connected to a substrate holder was used for self-biasing. The c-BN phase forms for all samples, irrespective of the deposition temperature, with a little amount of hexagonal phase existing as an intrinsic turbostratic boron nitride (t-BN) layer, whose thickness decreased with increasing temperature. The residual stress was maintained at a nearly constant compressive value. The adhesion improved markedly at high deposition temperature, but the insertion of the NCD buffer layer was ineffective in inhibiting the formation of t-BN layer under the present deposition condition.