Novel SiGe Source/Drain for Reduced Parasitic Resistance in Ge NMOS

Parasitic resistance issues are an important limitation of Germanium n-channel MOSFETs. We have experimentally investigated the use of SiGe as source/drain material to reduce the parasitic resistance. We have utilized circular TLM (transmission line method) measurement structures to extract the parasitic resistances of these SiGe layers. Results show about two orders of magnitude improvement in specific contact resistivity for insitu-doped n+ SiGe (20% Ge) over 100% n+ Ge layers, thus making it suitable for utilization as source/drain material in Ge NMOS transistors to reduce parasitic resistance, among other benefits.