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By Dr Mike Cooke
NEC reports that it has built scaled sub-10nm conventional
bulk planar MOSFETs with an improved on-off ratio. The new device technology
has been enabled through a new elevated source/drain extension (SDE) structure
achieved through special epitaxial growth techniques.
The SDE structure was created through a silicon
selective-epitaxial growth enabling a decrease in the effective junction depth.
The silicon surface for the source/drain doping region was raised with respect
to the channel region surface. The thicker, elevated SDE region realizes a
reduction in parasitic resistance and an enhancement in on-current.
By applying a tunneling epitaxial growth technique to the
gap region between the silicon-surface and sidewall-material, the thickness of
the elevated SDE can be self-aligned and easily controlled. This reduces
fluctuations in the elevation thickness, and improves productivity through ease
of manufacturing.
The technology can also be used to realize low power, high
performance system ICs for the 45nm technology generation and beyond.
Aggressive scaling of silicon device technology has been
hampered by the need to make source/drain junctions shallower to ensure steady
operation - hard to achieve with current doping techniques. Further, a
shallower layer is more resistive to electrical conduction.
The new technique simultaneously achieves controlled
elevation of the source/drain region and a significant improvement in the
on-off ratio, even for sub-10nm planar bulk transistors. NEC has even fabricated
6nm test- transistors.
NEC believes that this new research development proves the
potential for continuous and further technological advancement of
system-on-silicon LSI until 2020 through highly reliable, low-cost planar bulk
technology. This goes against the view that the standard industry transistor
structure will have to change from CMOS to ultra-thin body SOI
(silicon-on-insulator) or some double-gate structure,
The results of this research will be announced at the International
Electron Devices Meeting (IEDM) in Washington, DC, December 5 -7, 2005.
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