Epitaxial Germanium on SOI Substrate and Its Application of Fabricating High ION/IOFF Ratio Ge FinFETs

Integrating germanium (Ge) thin film on silicon-on-insulator (SOI) substrate and fabricating Ge fin field-effect transistors (FinFETs) are demonstrated in this paper. Directly grown Ge film on a high-resistivity thin SOI substrate provides a good platform for fabricating advanced Ge devices. The SOI structure could effectively suppress junction leakage; therefore, high ION/IOFF ratio (∼ 5 × 105, at VD = 0.1 V) of the drain current is achieved. Tri-gate structure provides better short-channel control abilities for the Ge FinFETs, and the drain-induced barrier lowering and threshold voltage (VTH) shift can be maintained at the level of ∼110 mV/V and ∼0.1 V, respectively, for Ge n-channel FinFET with Lchannel = 120 nm and WFin = 40 nm. Multifin Ge FinFET with Lchannel = 170 nm and WFin = 50 nm is also illustrated. Both N― and P―FinFETs possess high ION/IOFF ratio over 104. Besides, the subthreshold swing could be reduced around 25% after forming gas annealing.