Epitaxial germanium on soi substrate and its application of fabricating high i on I_OFF 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 I ONI_OFF ratio (∼5× 10⁵, at V_D=0.1V) 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 (V_TH) shift can be maintained at the level of ∼ 110 mV_V and ∼ 0.1 V, respectively, for Ge n-channel FinFET with L_channel=120nm and W_Fin=40nm. Multifin Ge FinFET with L_channel=170nm and W_Fin=50 nm is also illustrated. Both N-and P-FinFETs possess high I_ONI_OFF ratio over 10 ⁴. Besides, the subthreshold swing could be reduced around 25% after forming gas annealing.