Deposition chemistry in the Cat-CVD processes of the SiH4/NH3 system

Laser spectroscopic as well as mass-spectrometric techniques were employed to examine the deposition chemistry in the catalytic chemical vapor deposition processes of the SiH4/NH3, system. The absolute densities of NH, NH2 and SiH3 radicals were measured under various conditions. The densities of the stable products, H-2 and N-2, as well as those of the reactants, NH3 and SiH4, were also measured. The NH2 density is always higher than that of NH and both densities decrease by the addition of SiH4. The SiH3 density increases nonlinearly with the increase in the SiH4 pressure. The SiH3 density was found to be much higher than that of NH2 under near practical deposition conditions to fabricate Si3N4 films (an NH3 to SiH4 flow-rate ratio of 50:1, a total pressure of 20 Pa and a catalyzer temperature of 2300 K). No ammosilane molecules were identified, suggesting that the contribution of ammosilyl radicals to the film deposition is minor. Thus, NH, and SiH3 must be the major deposition species to form Si3N4. (C) 2003 Elsevier Science B.V. All rights reserved.