CHEMICAL VAPOR-DEPOSITION OF BORON-CARBIDE FROM BBR3-CH4-H2 MIXTURES IN A MICROWAVE PLASMA

Boron carbide coatings are deposited at moderate temperatures, equal to or lower than 600°C, from BBr3CH4H2 mixtures in a microwave plasma. The deposition rate, the composition and the microhardness of the deposits are studied as function of the deposition parameters. Amorphous B-C films are obtained in a large composition domain, ranging from pure boron to 40 at.% C, with deposition rates between 5 and 25 μm/h-1, principally as a function of temperature, total flow rate and inlet concentration of CH4. The amount of bromine incorporated in the solid is measured to be between 0.2 and 5 at.% according to the deposition conditions, and the deposit microhardness varies in the range 1000-5000 kg mm-2. The deposition process is discussed and it appears that the activated intermediate species containing carbon inhibit the deposition rate as the methane inhibits the deposition rate of boron carbide in the low temperature chemical vapour deposition of BCL3CH4H2. © 1990.