Cryogenic implantation for source/drain junctions in Ge p-channel (Fin)FETs

Abstract

We demonstrate record boron activation >4×10²⁰cm^-3 and contact resistivity of 1.7×10^-8Ω-cm² on p⁺-Ge using a single boron implantation process step at cryogenic temperature followed by a low temperature (400^oC) activation anneal. Unlike RT and hot (400^oC) implantation, cryogenic implantation also gives shallower junctions (maintaining lower R_sh) and higher I_ON/I_OFF ratio. Fin TEM and electrical data as well as device simulations for cryogenic, low energy BF₂ implanted epitaxial Ge fins indicate significant and scalable improvement in dopant activation vs room temperature implantation demonstrating feasibility of cryogenic implants for source/drain extensions of future 3D Ge channel p-FinFETs.