I. De et Cm. Osburn, Impact of super-steep-retrograde channel doping profiles on the performance of scaled devices, IEEE DEVICE, 46(8), 1999, pp. 1711-1717
Super-steep retrograded (SSR) channels were compared to uniformly doped (UD
) channels as devices are scaled down from 250 nm to the 50 nm technology n
ode, according to the scheme targeted by the National Technology Roadmap fo
r Semiconductors (1997), The comparison was done at the same gate length L-
gate and the same off-state leakage current I-off where it was found that S
SR profiles always have higher threshold voltages, poorer subthreshold swin
gs, higher linear currents, and lower saturation currents than UD profiles.
Using a simulation strategy that takes into account the impact of short-ch
annel effects on drive current, it was found that the improved short-channe
l effect of retrograde profiles is not enough to translate into a higher pe
rformance over the UD channels for all technologies. Hence, if the effectiv
e gate-dielectric thickness scales linearly with technology, retrograde dop
ing will not be useful from a performance point of view. However, if the sc
aling of the gate-dielectric is limited to about 2 nm, SSR profiles can giv
e higher drive current than UD channels for the end of the roadmap devices,
Thus, the suitability of SSR channels over UD channels depends on the gate
-dielectric scaling strategy. Simulations using a self-consistent Schroding
er-Poisson solver were also used to show that the impact of quantum mechani
cal (QM) effects on the long-channel characteristics of SSR and UD MOSFET's
will be similar.