REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION PATTERNS OF CARBIDE-CONTAMINATED SILICON SURFACES

Carbon contamination of silicon surfaces is a longstanding concern for growers of thin films who utilize silicon wafer substrates. This cont amination often takes the form of epitaxial beta-SiC particles which g row after the decomposition of adsorbed carbon-bearing molecules, and the subsequent reaction of the freed carbon with the silicon substrate . Positive identification of such SiC contamination is possible via re flection high-energy electron diffraction (RHEED). To provide a comple te demonstration and analysis of the relevant RHEED patterns, we prepa red within a ''silicon molecular beam epitaxy'' system carbide-contami nated silicon surfaces using procedures intended to foster such contam ination. With conventional RHEED instrumentation, we obtained transmis sion electron diffraction patterns which resulted from the passage of the RHEED electron beam laterally through the SIC particles. Compariso n with theoretically predicted patterns positively identifies the beta -SiC phase and shows that the particles are epitaxially aligned, with their cubic axes parallel to those of the substrate. {This finding is in agreement with the widely accepted model for the behavior of carbon on silicon surfaces [Henderson el al., J. Appl. Phys. 42, 1208 (1971) ]}. More typically during in-situ silicon substrate preparation for th in film growth, RHEED patterns indicating such contamination contain S iC spots which are mere vestiges of the complete transmission diffract ion patterns presented in this work.