Carbon incorporation into Si at high concentrations by ion implantation and solid phase epitaxy

We have studied the incorporation of heavily supersaturated C into Si using solid-phase epitaxy (SPE) of implanted amorphous layers. The strain in the Si1-xCx/Si heterostructures was measured using rocking curve x-ray diffraction. The microstructure and defect introduction were examined using ion channeling and transmission electron microscopy (TEM). The fraction of C located on substitutional lattice sites in the Si was monitored using Fourier transform infrared absorption spectroscopy and ion channeling at resonance energies. Carbon-depth profiles were monitored by secondary ion mass spectroscopy. The metastable solubility limit for the incorporation of C into Si by SPE was found to be 3.0-7.0 x 10(20) atoms/cm(3), which is over three orders of magnitude above the equilibrium solubility at the Si melting point. This limit was determined by the ability to regrow without the introduction of microtwins and stacking faults along {111} planes. We postulate the local bond deformation resulting from the atomic size difference between C and Si leads to the faceting of the amorphous-crystalline interface and allows defect introduction, thus limiting the C supersaturations achieved in Si by SPE. It was also found that the defect density in the regrown alloys could be reduced by higher SPE regrowth temperatures in rapid thermal anneal processing. (C) 1996 American Institute of Physics.