KINETIC-ANALYSIS OF POLYCRYSTALLINE SILICON GROWTH FROM SILANE USING A ROD-SUBSTRATE CVD REACTOR

Polycrystalline silicon ingots, which are intermediate products of single crystalline silicon wafers, are produced from silane by thermal CVD under atmospheric pressure. A rod-substrate reactor with a double tube was designed for analyzing the kinetics of this process. Growth rates of polycrystalline silicon were measured at 1073∼1173K under low pressures of silane (0.51∼2.0kPa) diluted with hydrogen. The simple configuration of the reactor allowed exact simulations of the distributions of gas velocity, temperature and silane concentration in the reactor by use of the Navier-Stokes equations, and the axial profile of silicon growth rates on the substrate was calculated. The surface reaction rate constant was estimated by comparing the calculated and the experimental profiles of the growth rates. Two approximate models were also developed. One is a simplified laminar-flow model, in which axial gradients of velocity and temperature are neglected, and the other is a film model, in which resistances to mass transfer are confined to the film around the substrate. Results of the three kinds of model analyses indicated that the experiments were performed under nearly surface reaction-controlling regions. The surface reaction rate constants were thus estimated in the higher temperature regime using the rod-substrate reactor. © 1990, The Society of Chemical Engineers, Japan. All rights reserved.