Physics and technology of ultra short channel MOSFET devices

It is pointed out that, as MOSFET channel lengths are scaled below about 0.15 mu m, nonstationary carrier transport effects become increasingly important. These effects can result in increased drain current over what is expected from stationary transport theory (i.e. velocity saturation), and in decreased hot-carrier energy spectrum spread, or carrier temperature, leading to improved device reliability. However, the magnitude of these effects depends strongly not only on channel length but also on overall device design such as channel doping configuration, drain junction depth, etc. Besides minimization of junction depths, optimal device design requires a super-steep-retrograde channel doping, with surface doping concentration no higher than mid-10/sup 16/ cm/sup -3/. This can be achieved with indium doping for NMOS, and antimony or arsenic doping for PMOS extreme submicron transistors.<>