Initial stage of cubic boron nitride film growth from vapor phase

Abstract

Low pressure inductively coupled plasma enhanced chemical vapor deposition (ICP–CVD) made it possible to deposit stoichiometric boron nitride (BN) films with thickness gradients in lateral direction, which clearly demonstrate the progresses of the cubic BN (c‐BN) growth. Under optimal deposition conditions, single‐phase c‐BN grows on the initially deposited sp²‐bonded BN layer, which had a critical sp²‐BN‐thickness of around 30–100 nm, depending on the substrate potential. It was also found that there exists a very close correlation between the c‐BN formation and Ar incorporation, which was lower than the detection limit in the sp²‐bonded BN layer, while approximately 0.4 at. % Ar was detected in the c‐BN layer. Furthermore, drastic change of the strained state in the film and the surface morphology upon the transition of the growth phase from sp²‐bonded BN to c‐BN was confirmed. As a whole, the comprehensive characterization of the initial progress of the c‐BN formation suggested that a highly compressed state in the atomistic local scale, not in the macro scale, should be essential for the c‐BN formation.