OBSERVATION OF SI OUT-DIFFUSION RELATED DEFECTS IN SIC GROWTH ON SI(001)

Good quality epitaxial beta-SiC growth on Si(001) substrates is conven tionally obtained by various chemical vapour deposition processes usin g the reaction of carbon and silicon-containing gases at high temperat ure (around 1300 degrees C). We explore here an alternative route, at lower sample temperature, where SiC growth is obtained by molecular be am epitaxy evaporation of Si with C2H4 cracking on a surface held at 8 50 degrees C. Preliminary IR analyses show the expected absorption ban d at 794 cm(-1) of beta-SiC with a damping coefficient of 0.02 close t o the theoretical value (0.01). Moreover, cross-sectional transmission electron microscopy and in-situ X-ray photoelectron spectroscopy stud ies revealed the presence of elemental Si on the SiC surface, related to out-diffusion of Si atoms from the substrate. This on-top diffusion generates large pyramid-shaped defects in the substrate along [011] d irections and contributes to the formation of strong SIC islands emerg ing above other SIC regions presenting more regular two-dimensional gr owth. High resolution figures obtained by zooming on these islands all ows us to probe their local polycrystalline atomic structure. These de fects are not characteristic of our growth process as they were observ ed previously using other growth methods. Investigations are under way to determine a growth procedure which suppresses the formation of the se defects.