Investigation of the BN films prepared by low pressure chemical vapor deposition

Abstract

Abstract A thermodynamic analysis of boron nitride (BN) films grown by the low pressure chemical vapor deposition (CVD) process using a boron trichloride (BCl3)–ammonia (NH3) reaction system with or without a carrier gas (H2 or N2) has been undertaken. The dependence of the products and their thermodynamic yields on the reaction parameters were also predicted. The results indicated that the major species of the products at equilibrium included solid phase BN and gaseous phase HCl in the BCl3–NH3 system with or without N2. The processing parameters for depositing BN on a graphite substrate using low pressure BCl3–NH3–N2 CVD, an optimized system, were investigated. Amorphous BN films, with some microcrystallinity, were successfully deposited onto graphite plates by low pressure CVD at 1100 K. As the input gas ratio of NH3/BCl3 increased, the mole fractions of boron and nitrogen increased and tended to approach stoichiometric composition, whereas that of chlorine decreased. After heat treatment at 2023 to 2123 K for 1.5 h, amorphous BN transformed into hexagonal BN. The extent of the phase transformation of BN films depends on the temperature and duration of heat treatment.