A reactor for chemical vapor deposition of silicon

A rotating disk reactor has been designed and built to study chemical vapor deposition of silicon. The process chosen is reduction of silicon tetrachloride in excess hydrogen at high temperatures (900 - 1200[degrees]C) and atmospheric pressure. The silicon single crystal substrate on which deposition was obtained is rotated at a speed in the range 300 - 1200 rpm. The reactor is designed to minimize the effects of natural convection, radial diffusion, and reactant gas recirculation. The rotating susceptor, to which the silicon wafer is attached, is heated by induction and the substrate temperature is measured by optical pyrometry. Significant variations in nucleation and growth rates of silicon on a silicon substrate have been observed. Microstructures associated with epitaxial and polycrystalline growth were obtained at different radial positions on the same wafer. These experimental results can be attributed largely to temperature gradients across the wafer and to the presence of trace impurities, such as oxygen and carbon, on the wafer surface. A new reactor design is proposed which includes the modifications necessary to obtain uniform epitaxial growth of silicon with the rotating disk system.