A comparative study of SiC epitaxial growth in vertical hotwall CVD reactor using silane and dichlorosilane precursor gases

Abstract

SiC epitaxial films grown in an inverted chimney CVD reactor are analyzed and compared for growth rates, doping concentration and surface morphology using silane-propane-hydrogen and dichlorosilane (DCS)-propane-hydrogen chemistry systems. A general 1-D analytical model is presented to estimate the diffusivity of precursor gases, boundary layer thickness and growth rates for both gas systems. Decomposition of precursor gases into Si growth species is investigated by a commercial simulation tool, Virtual Reactor (VR). DCS suppresses the formation of elemental Si at lower pressures, reduces precursor losses, and leads to increased growth rate. However, at higher pressures, even DCS decomposes into elemental Si, which contributes to high Si depletion, limiting the maximum achievable growth rate. Reduction of Si loss using DCS is verified by mass measurements of parasitic depositions in the injector tube. The doping concentration of the epitaxial film is governed by the effective C/Si ratio at the growth surface rather than the inlet C/Si ratio, which is examined at various growth pressures. In addition to the widely known Si-depletion, C-depletion is also shown to exist and it plays a critical role in determining the doping concentration at various growth conditions. Increased roughness for the DCS growth at higher pressures is addressed and attributed to excessive HCl etching at higher pressures.