Formation of buried epitaxial silicon carbide layers in silicon by ion beam synthesis

RBS/channeling, X-ray diffraction and transmission electron microscopy (TEM) as well as cross-sectional transmission electron microscopy (XTEM) are used to study the formation of well-defined, epitaxial 3C-SiC layers in Si(100) and Si(111) by high dose implantation of 180 keV C ions and subsequent thermal annealing at 1250 degrees C. The dose dependence of the carbon redistribution during the post-implantation anneal is studied in detail, revealing the possibility to grow well-defined substoichiometric and stoichiometric silicon carbide layers as well as 3C-SiC layers with a large concentration of excess carbon atoms. The presence of crystalline SiC nuclei in the as implanted state and their depth distribution are shown to be important for the carbon redistribution into a discrete layer during annealing. XRD monitoring of the epitaxial 3C-SiC component formed during implantation indicates the build-up of lattice distortions close to the stoichiometry dose. After annealing, the approximately 170 nm thick continuous SiC layers are covered by 300 nm thick crystalline silicon top layers, containing individual SiC precipitates. Cross-sectional TEM investigations reveal sharp interfaces between Si and SiC layers and almost unstrained Si on top and underneath the layers. First results are reported indicating that SiC can be formed also in homogenous deep buried layers using MeV ion beam synthesis.