Development of metal source/drain Ge-CMOS using TiN/Ge and HfGe/Ge contacts

Ge is of great interest as a candidate channel material for future CMOS devices due to its high intrinsic carrier mobility. To translate this potential into CMOS devices, it is desirable that the source/drain (S/D) junctions are composed by metal/Ge contacts. However, the Fermi-level pinning impedes the embodiments, by which the contact formation showing a low electron barrier height (Φ_BN) is very difficult. We have found TiN on Ge is superior as a low Φ _BN contact. In this paper, we present the detailed fabrication and the electrical performance of a TiN/Ge contact. Furthermore, we present the excellence of a HfGe/Ge contact showing a low hole barrier height (Φ_BP). Finally, we present the fabrication and device performance of metal S/D n- and p-MOSFETs using TiN/Ge and HfGe/Ge contacts, respectively.