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 cm² and 6.4 × 10^-7 Ω cm² 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 × 10²⁰ cm^-3 and a high electron concentration of 8.6 × 10¹⁹ cm^-3. Theoretical calculations indicate that to achieve ρ_c <; 1 × 10^-8 Ωcm² 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.