Microstructure of heteroepitaxial Si/CoSi2/Si formed by Co implantation into (100) and (111) Si

Abstract

Heteroepitaxial Si/CoSi2/Si structures have been synthesized by high-dose implantation of Co into (100) and (111) Si at an energy of 170 keV and subsequent annealing. In the as-implanted state the implanted Co is found to be present as CoSi2. For a dose of 2×1017 Co/cm2, the Co is present in the form of epitaxial precipitates, which exhibit both the aligned (A-type) CoSi2 and twinned (B-type) orientation. For a higher dose of 3×1017 Co/cm2, a monocrystalline epitaxial CoSi2 layer near the top of the implanted Co distribution is formed during the implantation. The heteroepitaxial structures that are formed in this way are fully aligned. In contrast, when these structures are formed by sequential surface deposition techniques, twinning occurs at every Si/CoSi2 interface. The formation of the aligned orientation of the buried CoSi2 layer can be attributed to the larger stability of aligned precipitates as compared to twin-oriented precipitates.