Physical Insights on Quantum Confinement and Carrier Mobility in Si, Si_0.45Ge_0.55, Ge Gate-All-Around NSFET for 5 nm Technology Node

Abstract

We present a comprehensive theoretical investigation of the quantum confinement limited mobility in the Si1-xGex-channel gate-all-around nanosheet field effect transistor for 5-nm node. The study encompasses physics-based quantum mechanical models both for P and NMOS with specified channel/wafer orientations and channel thicknesses: (1) k.p model with Poisson solver for band structures, bandgap variations, and confined charge distributions; (2) Kubo-greenwood model for low field mobility with considering surface roughness and stress; (3) multisub-band Boltzmann transport equation based on a state-of-the-art phase space approach is employed to evaluate device IV characteristics; and (4) the threshold voltage (VT) variations with different channel/wafer orientations are also evaluated. Our simulation study shows that {110} wafer Ge channel can be an attractive option for 5-nm node pMOS, and Si is still promising for nMOS due to strong quantum confinement in Ge channel.

Keywords

• Quantum confinement
• mobility
• GAA NSFET