Strain stabilization of SiGe films on Si(001) by in situ pre-epitaxial HCL etching

The effect of in situ chemical HCl etching of Si(0 0 1) substrates on the relaxation behavior of CVD-grown epitaxial Si0.77Ge0.23 films is studied by high-resolution X-ray diffractometry, atomic force microscopy, and etch pit delineation experiments. The intentionally induced, moderate interface roughness leads to a slight increase of the critical layer thickness as well as to a distinctly retarded relaxation for partly relaxed films on etched compared to non-etched substrates. Both effects are found to be caused by suppressed dislocation formation rather than by reduced dislocation glide. Since the etching procedure shows no detrimental effect on the crystal quality, a related process may be applied for the stabilization of epitaxial SiGe films with higher Ge contents, e.g. for the fabrication of the next generation SiGe HBTs.