Low contact resistances using carrier activation enhancement for Germanium CMOSFETs

We obtained low NiGe specific contact resistivities ρ
_c
of 4.4 × 10
^-8
Ω cm
²
and 6.4 × 10
^-7
Ω cm
²
for p- and n-type Ge, respectively. The key to achieving low ρ
_c
is carrier-activation enhancement (CAE), which uses Ge preamorphization implantation followed by B implantation or P/Sb co-implantation. These CAE techniques led to a record hole concentration of 8.4 × 10
²⁰
cm
^-3
and a high electron concentration of 8.6 × 10
¹⁹
cm
^-3
. Theoretical calculations indicate that to achieve ρ
_c
<; 1 × 10
^-8
Ωcm
²
as required for ITRS 2015, the contact process for PMOS needs further optimization and NMOS needs further CAE improvement and/or reduction in Schottky barrier height.