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

We demonstrate record boron activation >4×10
²⁰
cm
^-3
and contact resistivity of 1.7×10
^-8
Ω-cm
²
on p
⁺
-Ge using a single boron implantation process step at cryogenic temperature followed by a low temperature (400
^o
C) activation anneal. Unlike RT and hot (400
^o
C) 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 BF
₂
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.