20 nm Gate length Schottky MOSFETs with ultra-thin NiSi/epitaxial NiSi2 source/drain

Schottky barrier (SB)-MOSFETs with NiSi and epitaxial NiSi2S/D contacts with gate lengths as small as 20 nm are presented. Epitaxial NiSi2 FETs show higher on-currents than corresponding NiSi devices due to its lower SB height. A striking observation is that tunnelling currents through the fairly large SB decrease at very short gate lengths in SB-MOSFETs, in contrast to the scaling behavior of conventional MOSFETs. Simulations indicate that the potential in the channel increases due to overlap of the high source and drain barriers with decreasing gate length, leading to lower currents. Boron implantation into the silicide (IIS) was used to lower the SBH. Devices with epitaxial NiSi2 show an improved performance after barrier lowering by (IIS). It is shown, that the parasitic potential increase of the two S/D Schottky barriers can be either minimized by IIS and by enhanced gate control due to EOT scaling using high-k as the gate oxide.

► 20 nm Gate length SB-MOSFETs with NiSi and epitaxial-NiSi2S/D contacts were compared.
► Simulations and experimental show limited scaling behavior of MOSFETs.
► Implantation into silicide process improves the device performance.
► Low contact resistivity of epitaxial NiSi2 enhances the on-current.