EXTENDED MODEL FOR STRESS-INDUCED FORMATION OF C-BN IN ION-ASSISTED DEPOSITION

A simple model is presented that describes the formation of cubic boro n nitride (c-BN) during ion-assisted film deposition in terms of compr essive stress. The extended static stress model is based on the rate e quations of Davis, taking into account the balance of vacancies and in terstitials formed in the film during ion bombardment. The model expla ins 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 s tress necessary for c-BN formation. The stress as a function of ion en ergy and ion-to-atom arrival ratio can be described in terms of the mo mentum transferred to the film by the ions as the single independent v ariable. In the case of the bombarding species also representing the f ilm forming atoms (direct energy input), the boundary of the c-BN grow th domain is predicted to shift to lower ion-to-atom arrival ratios fo r 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 inc rease of the Young's modulus of c-BN compared to h-BN. (C) 1998 Elsevi er Science S.A.