MIT Department of Electrical Engineering & Computer Science
On the Universality of the Electron Mobility
and Degradation of the Total Gate Capacitance
in Scaled Silicon MOSFETs
Dragica Vasileska
Arizona State University
Wednesday, March 26, 1997
4:00 PM (3:45 refreshments)
Grier Room, Room 34-401A
EECS Special Seminar
Abstract
As MOSFETs are scaled to deep-submicron channel lengths,
it has become necessary to decrease the oxide thickness (to less
than 10 nm) and to increase the channel doping (Na=5x10^17 cm^-3
or more) in order to continue to maintain good control of the
channel by the gate. The high substrate doping leads to large
surface electric fields and significant quantization of the
carriers in the direction perpendicular to the interface, even
near the threshold of inversion. The non-uniformity of the doping
profile used in these state-of-the art devices affects the
magnitude of the weighting coefficients for the inversion and
depletion charge densities in the definition of the effective
transverse electric field used in obtaining the universal
mobility curves. This talk will present the results of some
recent theoretical studies, in which we have addressed some of
the above issues, including:
- The degradation of the total gate capacitance (which
determines MOSFETs transconductance) due to finite inversion layer
capacitance;
- The influence that depletion charge and surface-roughness
scattering have on the low-field mobility in scaled Si MOSFETs;
and
- Calculation of the appropriate weighting coefficients for
the inversion and depletion charge densities in the definition of
Eeff that lead to the universal mobility curves for devices with
uniform, step-like and retrograde doping profiles.
URL of this page:
http://www-eecs.mit.edu/AY96-97/events/23.html
Created: Mar 11, 1997
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Modified: Jun 24, 1997
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