Efforts at the Jet Propulsion Laboratory toward the production of pure polycrystaline silicon are centered on the concept of silicon particle growth in a fluidized bed reactor (FBR) and a continuous flow pyrolyzer (CFP). The CFP possibly can provide the seed particles which will be grown to larger sizes in the FBR. In both the reactors polycrystalline silicon is obtaned from the pyrolysis of silane. A part of the JPL effort is to develop a model of silicon particle growth for the purpose of predicting particle growth rates and product particle size distributions in the FBR and the CFP. This repot describes the mathematical models of silicon particle growth in the FBR and the CFP.

A computer-assisted thermochemical equilibrium analysis was conducted for the silicon transport reaction: Si(s) + SiF/sub 4/(g) = (intermediates) = Si(s) + SiF/sub 4/(g). The calculations indicated that a substantial transport rate should be possible at temperatures of 1700/sup 0/K and one atmosphere pressure. Computations were made to determine whether the elemental impurities present in metallurgical-grade silicon would transfer in this process. It was concluded that aluminum, chromium, copper, iron, manganese, molybdenum, nickel, vanadium, and zirconium would not transfer, but that boron, magnesium, phosphorus, and titanium would transfer.

Silane pyrolysis in a continuous flow pyrolyzer is a simple process that is currently being developed for producing solar cell grade silicon. The process involves complex phenomena, however, including thermal decomposition of silane, nucleation and growth of silicon particles, and mass and heat transfer. Modeling the effects of transport phenomena on silane pyrolysis in a continuous flow pyrolyzer is discussed. One- and two-dimensional models are developed to predict velocity, temperature, and concentration profiles in the reactor. The one-dimensional model has been implemented as a computer code.