NEC Corporation, the National Institute for Materials Science and the Japan
Science and Technology Agency announced the development of a
switching technology that migrates metal atoms in a solid electrolyte,
and makes it possible to manufacture low-cost, high-performance
programmable LSI devices for a wide range of applications. Called
NanoBridgea, the switching technology already has been successfully
demonstrated in a prototype circuit. Results of the joint research
project will be presented February 17 at the International Solid-State
Circuit
Conference (ISSCC) in San Francisco.
NanoBridge technology uses the atom switching effect of a nanoscale
metal bridge, in which an electrically conductive channel is created or
annihilated by stretching a metallic bridge controlled by an
electrochemical reaction inside a solid electrolyte. With an
easy-to-fabricate, highly stable junction structure and a solid
electrolyte (Cu2S) with high process
immunity, the NanoBridge stabilizes
the LSI wiring layer.
As a result, the operating speed of a programmable LSI device, which is
indispensable for short-term equipment development, can be increased and
the area of the chip reduced, thus improving performance and lowering
costs in electronic appliances such as mobile equipment and digital
televisions.
Reconfiguration of the circuit also makes it possible to use a single
chip for many different functions. For example, in a multi-functional
cell phone of the future, having to use dedicated LSI chips for each of
those functions would make mounting of the chips problematic in a small
case. Using a high-performance programmable LSI device not only would
enable all of the functions, including heavy processing, to be done by
one chip, it also would facilitate additional processing capabilities by
means of communication.
A semiconductor chip is an important component for controlling
electronic appliances. Dedicated ASICs, usually cell-based ICs, tailored
to match each appliance are widely used. However, competition in the
development of appliances recently has become fierce, heightening the
importance of reducing development time. As a result, the market share
for programmable LSI devices that enable a designer to change a circuit
locally has been increasing. Since conventional programmable LSI devices
are more expensive and slower in operation than cell-based ICs, the
demand is for a low-cost, high-performance programmable LSI chip on a
par with a cell-based IC.
NEC Corporation, the National Institute for Materials Science, and the
Japan Science and Technology Agency have for some time been promoting
joint applied research concerning materials, devices and circuits in
order to overcome these problems. The team used NanoBridge technology to
make a prototype 4'4 crossbar, which is the basic circuit indispensable
for a programmable LSI device, and then changed the voltage application
pattern to successfully realize repeated circuit reconfiguration.
About one-thirtieth the size of the SRAM and pass transistor circuit
reconfiguration switch used in a conventional programmable LSI device,
the NanoBridge switch can be incorporated directly into the wiring
layer. It has one-twentieth or less the resistance of the conventional
switch.
The compact NanoBridge circuit reconfiguration switch is laminated with
the logic block, reducing its chip area to a fraction of a conventional
chip's thus resulting in lower costs.
The unit circuit block has been made as small as a primitive gate, and
overhead in the circuit configuration has been reduced, thus enabling a
wide range of applications to be efficiently realized using a circuit
that has been reduced to 1/10th the scale of conventional circuits. The
circuit's power efficiency has been improved by around 300% due to the
reduction in circuit area.