Pyrolysis Mechanism of Silanes, Difluorosilane, and Their Mixtures

Pyrolysis of silanes, difluorosilane, and their mixtures has been observed by mass spectroscopy under isothermal con-ditions. The rates of Sill4 pyrolysis show a large compensation effect at low pressure, which agrees with the theory of uni-molecular reaction. The pyrolysis rates of difluorosilane and silanes are enhanced synergistically when they are mixed together. The reaction mechanism proposed in this study for pyrolysis of the Si-containing species explains the observed experimental results well. Infroduction Chemical vapor deposition (CVD) proceeds by two reac-tion steps, i.e., homogeneous reaction to produce the film precursors in the gas phase and heterogeneous reaction to decompose the precursors on the substrate surface. Homogeneous reaction is important because in many cases it determines the overall rate of the CVD process and also affects the quality of the deposited film.'-7 Silanes (SiJ15) and chiorosilanes (SiH,Cl2) are commo