Chemical Vapour Deposition of AIN-Si₃N₄ Codeposits

Abstract
A hot wall CVD reactor has been especially adapted to the problem of producing codeposits of aluminium and silicon nitrides. The experimental set-up for preparing "in situ" aluminium trichloride or a mixture of AlCl₃ and SiCl₄ by the action of silicon tetrachloride on an aluminium supply, heated to temperatures (Tc) between 380 and 520 °C is presented. A study was also made of the deposition kinetics using a thermobalance with a continuous recording facility. The deposition kinetics of AIN and Si₃N₄ were measured and compared. The codeposits prepared at a temperature of 1200 °C and a total pressure of 1 Torr were found to be adherent when deposited on a graphite substrate covered by a layer of silicon carbide obtained by pyrolysis of tetramethylsilane at 1240 °C. The deposits were characterized by a variety of methods : X-ray diffraction, wavelength dispersive spectroscopy and scanning electron microscopy.