On the mechanisms of cubic boron nitride film growth

Abstract

Cubic boron nitride (c-BN) is the most attractive BN allotrope due to its outstanding physical and chemical properties. Deposition of c-BN films is typically accomplished using ion-assisted physical vapor deposition methods. Recently, low-stress and thick c-BN films were successfully grown by chemical vapor deposition approaches. It was also shown that c-BN growth is possible by ion implantation with ion energies above 10 keV. Independent of the deposition method, there exist pronounced similarities regarding the nucleation and growth conditions as well as the film structure. Despite these similarities, the different c-BN growth methods are most probably based on different underlying physical processes. This is reflected in characteristic differences in the c-BN growth conditions, such as different ion energy and growth temperature regimes, and different chemical precursors. In this contribution the growth conditions for several c-BN growth methods are compared and an attempt will be made to extract the relevant physical processes for c-BN growth. We propose three different major processes leading to c-BN growth: (i) the subplantation process taking place in ion-assisted PVD and ion beam deposition; (ii) a process involving gas phase and surface chemistry taking place in fluorine-assisted plasma-CVD at high temperatures; and (iii) internal growth during B and N ion implantation into c-BN bulk material.