REVIEW OF ADVANCES IN CUBIC BORON-NITRIDE FILM SYNTHESIS

Cubic boron nitride (cBN) has a number of highly desirable mechanical, thermal, electrical, and optical properties. Because of this, there h as been an extensive worldwide effort to synthesize thin films of cBN. Film synthesis is difficult in that without significant levels of ion bombardment during growth, only sp2-bonded BN forms, not sp3-bonded c BN. Recently there has been considerable progress in improving the dep osition techniques and cBN film quality. In addition, progress has bee n made in understanding how energetic deposition conditions can lead t o cBN formation. However, unanswered questions remain and process impr ovements are still needed. In this paper we critically and comprehensi vely review recent developments in cBN film synthesis and characteriza tion. First, the structures and stability of the BN phases and charact erization techniques are described. Next, the key experimental paramet ers controlling cBN film formation and synthesis techniques are discus sed. Following a review of microstructure, the proposed mechanisms of cBN formation and the observed mechanical and electrical properties of cBN films are analyzed. We conclude by highlighting the current imped iments to the practical realization of cBN-film technology. (C) 1997 P ublished by Elsevier Science S.A.