DEPOSITION OF BORON-NITRIDE FILMS FROM BB'B''-TRICHLOROBORAZINE

The Chemical Vapor Deposition of boron nitride from BB'B''-Trichlorobo razine was investigated in a microbalance equipment with a hot wall re actor. It was possible to monitor the evaporating and depositing masse s simultaneously, so that the kinetics of the CVD-process could be mea sured in detail. The evaporation rate was studied in the temperature r ange between 285 and 330 K. The activation energy of the evaporation w as determined to be 65 +/- 2 kJ/mole. The deposition process was inves tigated at temperatures between 973 and 1233 K in an argon atmosphere at total pressures between 250 and 2000 Pa. The deposition of boron ni tride 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 tim e of the precursor in the hot zone of the reactor. The deposited layer s were colorless and amorphous and had the correct 1/1 stoichiometry b etween boron and nitrogen (WDX-AnaIysis). The layers contained less th an 1 % of chlorine. SiC-Tyranno-fiber fabrics were coated homogeneousl y with BN layers of 200-300 nm thickness. A tensile strength decrease of approximately 15 % was observed for the coated fibers. Oxidation ex periments showed that the layers were oxidized at temperatures above 8 73 K in an Ar/O-2-atmosphere leading to a brittle behavior of the fibe rs.