Selective Area Growth of Si-Ge Using Single Source Silylgermanes

Employing selective epitaxy to grow fully strained Si-Ge alloys in the source and drain (S/D) of a p-type metal-oxide semiconductor (PMOS) transistor compresses the Si-channel to significantly increase the hole mobility, and consequently, the speed of the device. Ge-rich alloys, where Ge constitutes = 50% of the alloy, are of particular interest because of expectations that these alloys will produce disruptive improvements in the saturation/drive currents over traditional, Si-rich, configurations. Still, current selective growth processes are unable to yield films with device quality morphology and microstructure for the desired Ge range. Likewise, conventional processes produce high dislocation densities, non-uniformities in strain, lack of compositional control, and reduced film thickness in Ge-rich films, which ultimately can degrade the quality and performance of the stressor material, subsequently, limiting the practical usefulness of these approaches. Researchers at Arizona State University have developed a device quality method to selectively deposit Si-Ge materials, specifically Ge-rich Si-Ge materials, on substrates. This method exploits the unexpected and unique growth properties of Si-Ge hydride compounds to selectively deposit Si-Ge layers, for example, as strained-layered heterostructures of Ge-rich semiconductors in the S/D regions of PMOS structures. The method achieves high strain states in Si-Ge layers that are typically much thicker than the nominal equilibrium critical thickness during blanket growth. Potential Applications Semiconductors (e.g. CMOS, NMOS, PMOS, MOSFET, etc.) Microelectronics Optoelectronics (e.g. Photodiodes, etc.) Benefits and Advantages Provides Selective Area, Device Quality, Ge-Rich Si-Ge Alloys allows selective growth (renders high mobility devices and opens path to III-V integration with Si); produces monocrystalline microstructures, smooth and continuous surface morphologies, and low defect densities; demonstrates 50 75% Ge content compared to the 20 30% content of existing approaches Provides High Strain - up to 2.3 % demonstrated in blanket growth and typically much thicker than the nominal equilibrium critical thickness Operates at CMOS-Compatible Low Temperatures heteroepitaxy at 300 - 450C Offers Simple Integration single source precursor eliminates the need for multi-component reactions and corrosive etching processes; high levels of controllability and uniformity Download original PDF