Catalytic CVD processes of oxidizing species and the prevention of oxidization of heated tungsten filaments by H2

The catalytic decomposition conditions of O2, N2O and NO were investigated to avoid oxidization of heated tungsten filaments. It was confirmed that no oxidization takes place in the presence of an excess amount of H2 or NH3: for example, when the catalyzer temperature is 1990 K and the H2/O2 flow rate ratio is more than 18. These results are consistent with the recent results that no oxidization is observed in the SiH4/NH3/H2/O2/He system to deposit SiOxNy films as long as the O2 flow rate is low. In addition, it was revealed that in this SiH4/NH3/H2/O2/He system, O2 is not only decomposed on the catalyzer surfaces but also is consumed in homogeneous and/or heterogeneous reactions. One of the consumption paths in the gas phase should be the reaction with SiH3 to produce SiO