A novel approach to Si_0.5Ge_0.5 channel FinFET fabrication: utilizing a three-layer SiGe strain relaxation buffer and In-Situ phosphorus doping

In this paper, a novel in-situ phosphorus doped three-layer SiGe strain relaxed buffer (SRB) is proposed in order to realize the integration of medium Ge mole fraction SiGe channel on the Si substate. Firstly, a three-layer SiGe SRB is epitaxially grown on a Si substrate, with the Ge mole fraction of each layer decreasing from 30 to 10% from top to bottom, and only top Si_0.7Ge_0.3 SRB is in-situ doped with a phosphorus concentration of 5E17 cm⁻³. After a chemical mechanical planarization (CMP) treatment is applied to the surface of top Si_0.7Ge_0.3 SRB, a high quality and almost fully strained SiGe layer with a Ge mole fraction of 50% is prepared to realize the Si_0.5Ge_0.5/in-situ doped three-layer SiGe SRB stacked structure. Moreover, based on this stacked structure, a Si_0.5Ge_0.5 channel p-FinFET with subthreshold swing of 94 mV/dec and driven current of 103 µA/µm is successfully prepared. Its Si_0.5Ge_0.5 channel FinFET achieves better electrical performance after its in-situ P doping concentration of Si_0.7Ge_0.3 SRB layer increases from 1 × 10¹⁷ cm⁻³ to 5 × 10¹⁷ cm⁻³ due to stronger inhibition of sub-fin parasitic channels and punch-through leakage. It proves that this newly developed in-situ phosphorus doped three-layer SiGe SRB would be a practical technique for the integration of medium Ge mole fraction SiGe channel FinFET.