Extended model for stress-induced formation of c-BN in ion-assisted deposition

Abstract

Abstract A simple model is presented that describes the formation of cubic boron nitride (c-BN) during ion-assisted film deposition in terms of compressive stress. The extended static stress model is based on the rate equations of Davis, taking into account the balance of vacancies and interstitials formed in the film during ion bombardment. The model explains the lower boundary of the c-BN growth domain in the diagram of ion-to-atom arrival ratio and ion energy in terms of a critical minimum stress necessary for c-BN formation. The stress as a function of ion energy and ion-to-atom arrival ratio can be described in terms of the momentum transferred to the film by the ions as the single independent variable. In the case of the bombarding species also representing the film forming atoms (direct energy input), the boundary of the c-BN growth domain is predicted to shift to lower ion-to-atom arrival ratios for constant ion energy. Once c-BN has formed, the ion energy and ion-to-atom arrival ratio can be lowered to keep c-BN growing due to the increase of the Young's modulus of c-BN compared to h-BN.