| Media
Contacts:
Dr. Marco Buongiorno
Nardelli, 919/513-0514
Paul K. Mueller,
News Services, 919/515-3470
June
12, 2003
Breakthrough
“Interface Tuning” is Macro Step for Microelectronics
FOR
IMMEDIATE RELEASE
| The
ability to make atomic-level changes in the functional
components of semiconductor switches, demonstrated
by a team of Oak Ridge National Laboratory, North
Carolina State University and University of Tennessee
physicists, could lead to huge changes in the
semiconductor industry. The results are reported
in the June 13 issue of Science.
Semiconductor devices, the building
blocks of computing chips that control everything
from coffee makers to Mars landings, depend on
microscopic solid-state transistors, tiny electronic
on-off switches made of layers of metals, oxides
and silicon. These switches stop and start the
flow of electrons, and work themselves because
of the microscopic interface between the oxide
layer and the silicon layer, in the realm of individual
atoms, where minute positive and negative charges
determine semiconductor success or failure.
|
This
image illustrates the concept of “Coulomb
buffer,” the region between oxide (above)
and silicon (below) in nanoswitches, that can
be “tuned” through atomic-level
manipulation for desirable semiconductor characteristics,
an advance that benefits both researchers and
manufacturers.
|
Until now, researchers – and the
multibillion-dollar semiconductor industries they support
– had to accept the limitations that each crucial
interface contains.
But researchers at Oak Ridge, NC State and Tennessee
have successfully learned to “tune” the
atomic-level zone between substances, in a development
that they call “a unifying concept for understanding
and designing” this aspect of semiconductor physics.
According to Dr. Rodney McKee at Oak Ridge, the concept
arose from “a reformulation of the classic Schottky
Barrier problem that will impact everything in semiconductor
technology from laser diodes to field-effect transistors
in high-speed logic.”
The
U.S. Department of Energy’s Office of Science
funded the team’s research. The Oak Ridge National
Laboratory is a Department of Energy facility.
The atomic tuning, described in the paper “The
Interface Phase and the Schottky Barrier for a Crystalline
Dielectric on Silicon,” takes place in what Dr.
Marco Buongiorno Nardelli, assistant professor of physics
at NC State and one of the authors of the paper, has
named the “Coulomb buffer.” Here, at the
boundary between silicon and oxide, there is an interface
phase that is neither silicon nor oxide but its own
hybrid structure.
Buongiorno Nardelli, studying this interface
phase at the atomic level using high-performance computer
simulations, found that the fundamental basis for this
tuning was in increasing or decreasing the electronic
“dipole charge” – the microscopic
arrangement of positive and negative charges at the
interface.
The physicists’ sophisticated
experiments demonstrated that the Schottky barrier –
the boundary at the edge of a substance where electrons
are confined, long considered an inflexible limitation
– can in fact be manipulated, and that “barrier
height” is, in Buongiorno Nardelli’s words,
“no longer a problem, but an opportunity.”
According to the NC State physicist,
who holds a joint appointment at Oak Ridge National
Laboratory, the team’s work will “change
common beliefs” in the field of semiconductor
physics, and could open the way for smaller, faster
and smarter computers.
And manufacturers, able to tune the
atomic dipoles in the Coulomb buffer for specific electronic
characteristics, may find that this discovery deep in
the micro-regions enables macro-steps forward in efficiency
and productivity.
-mueller-
Note
to editors: The abstract of the Science
paper follows.
“The
Interface Phase and the Schottky Barrier for a Crystalline
Dielectric on Silicon”
Authors: R.A. McKee, F.J. Walker, M. Buongiorno
Nardelli, W.A. Shelton, G.M. Stocks
Date: Published in the June 13 issue of Science.
Abstract:
The barrier height for electron exchange at a dielectric-semiconductor
interface has long been interpreted in terms of Schottky’s
theory with modifications from gap states induced in
the semiconductor by the bulk termination. Rather, we
show with the structure specifics of heteroepitaxy that
the electrostatic boundary conditions can be set in
a distinct interface phase that acts as a “Coulomb
buffer.” This Coulomb buffer is tunable and will
functionalize the barrier-height concept itself.
|
Raleigh,
NC 27695
