Cl_nH_6-nSiGe compounds for CMOS compatible semiconductor applications: Synthesis and fundamental studies

We describe the synthesis of a new family of chlorinated Si-Ge hydrides based on the formula Cl_nH_6-nSiGe. Selectively controlled chlorination of H₃SiGeH₃ is provided by reactions with BCl₃ to produce ClH₂SiGeH₃ (1) and Cl ₂HSiGeH₃ (2). This represents a viable single-step route to the target compounds in commercial yields for semiconductor applications. The built-in Cl functionalities are specifically designed to facilitate selective growth compatible with CMOS processing. Higher order polychlorinated derivatives such as Cl₂SiHGeH₂Cl (3), Cl₂SiHGeHCl ₂ (4), ClSiH₂GeH₂Cl (5), and ClSiH ₂GeHCl₂ (6) have also been produced for the first time leading to a new class of highly reactive Si-Ge compounds that are of fundamental and practical interest. Compounds 1-6 are characterized by physical and spectroscopic methods including NMR, FTIR, and mass spectroscopy. The results combined with first principles density functional theory are used to elucidate the structural, thermochemical, and vibrational trends throughout the general sequence of Cl_nH_6-nSiGe and provide insight into the dependence of the reaction kinetics on Cl content in the products. The formation of 1 was also demonstrated by an alternative route based on the reaction of (SO₃CF₃)SiH₂-GeH₃ and CsCl. Depositions of 1 and 2 at very low temperatures (380-450°C) produce near stoichiometric SiGe films on Si exhibiting monocrystalline microstructures, smooth and continuous surface morphologies, reduced defect densities, and unusual strain properties.