REACTION OF DIBORANE AND AMMONIA GAS-MIXTURES IN A CHEMICAL-VAPOR-DEPOSITION HOT-WALL REACTOR

Boron nitride has been deposited by chemical vapor deposition from diborane and ammonia gas mixtures, in the form of either films or powders depending on the pressure in the reactor. IR analysis of the boron nitride deposits has been used to obtain the composition of the films. In the temperature range studied, 600-850-degrees-C, the effect of the deposition temperature on the reaction kinetics has been interpreted by assuming a change in the relative concentration of activated species arising from diborane and ammonia molecules. This change modifies the reaction path followed in the boron nitride synthesis through the formation of different intermediate compounds: aminodiborane in the low-temperature range (<700-degrees-C) and borazine at the higher temperatures (greater-than-or-equal-to 775-degrees-C). The presence of either of these intermediate compounds determines the deposition rate and the final composition of the boron nitride films.