Preparation and Properties of Thin Film Boron Nitride

Clear, vitreous films of boron nitride up to 6000A thick have been deposited on a variety of substrates at 600~176 by a reaction between diborane and ammonia in hydrogen or inert carrier gas. Deposition rate may be readily ad-justed to 50-1000 A/rain. Most samples were made at either 600 ~ or 800 ~ with some attendant variation in film properties. The 600 ~ material contains some residual B-H bonding. The film is essentially amorphous to electron diffrac-tion. The refractive index is 1.7-1.8, the 1 MHz dielectric constant ~ 31/2, the dielectric strength ~--5x106 v/cm, and the 25 ~ resistivity-- ~ 1014 ohm-cm. The band gap is 3.8 ev and the phonon temperature in the neighborhood of 2000~ For semiconductor junction protection boron nitride has no advantage over sil-icon nitride. 600 ~ deposition directly on Si has produced surface charges as low as 4xl01l/cm 2,but there are room-temperature drifts, and high-field con-duction also. BN deposited at 800 ~ on Si is electrically similar to silicon nitride. Etching of BN film also presents the same problems as does silicon nitride. B