Deposition of Boron Nitride Films from BB'B"-Trichloroborazine

Abstract
The Chemical Vapor Deposition of boron nitride from BB'B''-Trichloroborazine was investigated in a microbalance equipment with a hot wall reactor. It was possible to monitor the evaporating and depositing masses simultaneously, so that the kinetics of the CVD-process could be measured in detail. The evaporation rate was studied in the temperature range between 285 and 330 K. The activation energy of the evaporation was determined to be 65 +/- 2 kJ/mole. The deposition process was investigated at temperatures between 973 and 1233 K in an argon atmosphere at total pressures between 250 and 2000 Pa. The deposition of boron nitride on silicon could be described by a Langmuir reaction type. A gas phase decomposition of BB'B''-Trichloroborazine was observed, so that the concentration at the substrate was dependent on the residence time of the precursor in the hot zone of the reactor. The deposited layers were colorless and amorphous and had the correct 1/1 stoichiometry between boron and nitrogen (WDX-Analysis). The layers contained less than 1 % of chlorine. SiC-Tyranno-fiber fabrics were coated homogeneously with BN-layers of 200-300 nm thickness. A tensile strength decrease of approximately 15 % was observed for the coated fibers. Oxidation experiments showed that the layers were oxidized at temperatures above 873 K in an Ar/O₂-atmosphere leading to a brittle behavior of the fibers.