Germanium-based Transistors for Future High Performance and Low Power Logic Applications
High mobility channel materials could replace strained Si to enhance speed performance and/or reduce power consumption in future transistors. Ge has the highest hole mobility among common elemental and compound semiconductors, and an electron mobility that is two times larger than that of Si. Ge is thus a promising channel material for future CMOS (Fig. 1). Key challenges include cost-effective integration of Ge on Si in a manufacturable process, formation of high-quality gate stack on Ge for n- and p-FETs at aggressively scaled EOTs that deliver high channel mobilities, and leakage issues related to its small bandgap. In this paper, we discuss recent research progress in advancing Ge-based transistor technologies. Integration of Ge on Si substrate to enable fabrication of high performance devices and formation of high-quality gate stack for Ge FETs (particularly for n-FETs) will be discussed. We also explore opportunities to boost the mobility of Ge, e.g. by incorporating Sn in Ge to form Ge 1-x Sn x . Furthermore, by raising the Sn composition, the band gap E G of Ge 1-x Sn x becomes smaller and transits from indirect to direct, making Ge 1-x Sn x a promising material for tunneling transistors. authors: Yee-Chia Yeo, Xiao Gong, Mark J. H. van Dal, Georgios Vellianitis, Matthias Passlack
Logic
High Mobility Channel
Silicon has been the transistor channel material of choice throughout all CMOS technology generations up until our 7nm node. TSMC’s 5nm technology is the first advanced logic production technology featuring SiGe as the channel material for p-type FinFET.
TSMC is actively exploring alternative transistor channel materials as an additional degree of freedom in the design of high performance and low power devices. Silicon-germanium and germanium are examples of TSMC’s exploratory research work, which has been extensively published and in some cases recognized as highlights in international conferences.
