Effects of time-dependent substrate biasing and gas composition on the nucleation of cubic boron nitride thin films

Boron nitride (BN) thin films were deposited on silicon and sapphire substrates by an inductively coupled plasma chemical vapor deposition technique with time-dependent control of the substrate dc bias (Vdc). Turbostratic BN films were deposited on sapphire when the bias reduction rate, ·Vdc, was optimized specifically for cBN growth on silicon. This difference depending on the substrates was explained by a potential drop in the dielectric substrate. By reducing ·Vdc at the early stage of deposition, the cBN phase was successfully deposited on both substrates. We also found that the chemical composition of BN varied from B/(B + N) = 0.48 to 0.57 upon changing the gas ratio of diborane to nitrogen. The gas ratio for film nonstoichiometry resulted in a thicker initial layer, i.e., the delayed nucleation of cBN.