GROWTH-KINETICS OF POLYCRYSTALLINE SILICON FROM SILANE BY THERMAL CHEMICAL VAPOR-DEPOSITION METHOD

The growth rates of polycrystalline silicon by thermal chemical vapor deposition from silane diluted in hydrogen and helium were measured in higher temperature range of 973–1173 K at 1 atm using a rod reactor with a double tube. The experimental conditions and the reactor configuration were carefully determined so that mass transfer at the surface of a substrate might not be dominant in the overall growth rate. Deposition mainly occurred from heterogeneous silane pyrolysis, for ambient hydrogen reduced homogeneous silane pyrolysis. A general partial differential equation model was derived, in which both surface reaction and mass transfer near the rod were considered. The distributions of silane concentration, temperature, and gas velocity in the reactor were calculated by the finite difference method, yielding the growth rate profile on the surface of the silicon rod in an axial direction. The rate constant of polycrystalline silicon deposition was estimated from curve fitting of the simulated growth rate profile and the experimental one by use of the nonlinear least squares method. A rate formula was determined in the temperature range 1073–1173 K and with the mole fraction of silane up to 2% in hydrogen atmosphere, assuming a chemical reaction mechanism on the growing surface by taking account of the reaction of hydrogen gas with adsorbed species. © 1990, The Electrochemical Society, Inc. All rights reserved.