Physical Mechanisms of Mobility Enhancement in Ultrathin Body GeOI pMOSFETs Fabricated by HEtero-Layer-Lift-Off Technology

Abstract

Advanced channel formation technologies called HEtero-layer-lift-off utilizing SiGe heteroepitaxy have been realized for fabricating ultrathin body (UTB) Ge-on-insulator (GeOI) structures. Insertion of SiGe etching stop layer was found to be effective for reducing GeOI body thickness ( $T_{\mathrm {body}}$ ) fluctuation. Backside Si passivation for Ge/buried oxide interface has been verified to suppress backside Coulomb scattering and help to induce volume inversion effect. With improvement of backside interfacial quality and precise control of GeOI $T_{\mathrm {body}}$ , primary carrier scattering factors in GeOI channel have been effectively reduced, resulting in significant improvement of hole mobility. High hole mobility of ~150 cm2/Vs in UTB GeOI pMOSFETs without strain technology has been demonstrated, which also outperformed Si universal mobility by 1.5 times even under $T_{\mathrm {body}}$ of 9 nm. With low-thermal-budget process compatibility, UTB GeOI platform is very promising for future Ge large-scale integrated circuits devices used in monolithic 3-D integration scheme.