CHEMICAL-VAPOR-DEPOSITION OF ALN-SI3N4 CODEPOSITS

A hot wall CVD reactor has been especially adapted to the problem of p roducing codeposits of aluminium and silicon nitrides. The experimenta l set-up for preparing ''in situ'' aluminium trichloride or a mixture of AlCl3 and SiCl4 by the action of silicon tetrachloride on an alumin ium supply, heated to temperatures (Tc) between 380 and 520 degrees C is presented. A study was also made of the deposition kinetics using a thermobalance with a continuous recording facility. The deposition ki netics of AIN and Si3N4 were measured and compared. The codeposits pre pared at a temperature of 1200 degrees C and a total pressure of 1 Tor r were found to be adherent when deposited on a graphite substrate cov ered by a layer of silicon carbide obtained by pyrolysis of tetramethy lsilane at 1240 degrees C. The deposits were characterized by a variet y of methods : X-ray diffraction, wavelength dispersive spectroscopy a nd scanning electron microscopy.