Contact resistance reduction for strained N-MOSFETs with silicon-carbon source/drain utilizing aluminum ion implant and aluminum profile engineering

Abstract

We demonstrate a novel technique to reduce the nickel silicide (NiSi) contact resistance Rcon in strained n-channel MOSFETs (n-FETs) with silicon carbon (Si:C) stressors, where a presilicide aluminum (Al) implant is performed and the Al profile is found to be affected by carbon (C). Al diffusion during silicidation is retarded by the presence of C and a high Al concentration is retained within the NiSi:C film, which is considered to be the main reason for electron barrier height ΦBn reduction in NiSi:C contacts. Ge preamorphization implant prior to Al implant further reduces the ΦBn to 0.44 eV. Integration of this technique in n-FETs with Si:C stressors achieves a 50% reduction in source/drain series resistance and 12% enhancement in saturation drive current. Negligible impact on the device short-channel effects is observed. When Al segregates at the NiSi/Si interface, the hole barrier height ΦBp is lowered, and such an Al profile can be used for the p-FETs. Al profile engineering shows a promise as a single-metal-silicide solution for selective Rcon optimization in CMOS. © 1963-2012 IEEE.