Introduction - Implications of Emerging Micro-and Nanotechnologies - page 2

because the technology has advanced. We complain about the demands of ubiq-
uitous connectivity as we attach cell phones to our belts and of information
overload as we put more and more material on our Internet servers. Over this time
span, transistors have gone from macroscopic, ~1-millimeter junction-length de-
vices, to ~90-nanometer gates in the latest commercial chips and to ~10-nanom-
eter gates in laboratory devices. This linear scaling clearly must end as devices
approach the size of atoms (~0.2 nanometers). This does not, however, mean that
progress in electronics and information technology will come to a halt. The
integrated circuit paradigm that has enabled this dramatic scaling improvement is
a planar, two-dimensional concept based on an interconnection of three-terminal
switching elements (transistors). 2 Moving to a volumetric approach, new materi-
als, and different computing strategies will probably allow continuation and even
acceleration of the capabilities and function per weight/volume/power of elec-
tronics. The practical success of miniaturization has been the result of the accom-
panying dramatic reduction in cost per function achieved by the integration of so
many electronic devices onto single chips and using parallel, or batch, fabrication
technologies to allow this cost scaling.
Less well understood is the acceleration in other micro- and nanotech-
nologies, which is being driven by miniaturization and is contributing to the
increasing density of information transmitted, stored, and processed. The growth
in magnetic information storage in recent years has been even more rapid than
growth in electronic information processing. 3 Advances in magnetic memory
storage range from new giant magnetoresistive nanoscale layered materials to
read heads flying 10 nanometers over the surface of magnetic discs moving at
speeds of 20 meters/second. To appreciate the challenge in control of tolerances
for this technology, scaling to the macro world by the relative lengths of a mag-
netic read head and an F-18 jet fighter would correspond to flying the F-18 only
100 micrometers above the ground, which has been polished to a smoothness of
10 micrometers and staying on course within an accuracy of 100 micrometers.
Optical information transmission has also been increasing at growth rates compa-
rable to that for magnetic memories, aided by control of materials—for example,
in optical fibers with ultrahigh-purity microscale cores and semiconducting lasers
with nanoscale quantum wells.
Mechanical devices at the microscale and below promise to further extend
the reach of miniaturized technologies. Microelectromechanical systems (MEMS)
build on the manufacturing paradigm of microelectronics and offer the promise
of large-scale batch fabrication at low cost. Currently this emerging technology is
primarily focused on simple devices such as inertial sensors for air bag release in
automobiles and microscale mirrors for optical projection and switching. How-
ever, future applications of MEMS for airfoil control, inertial sensing, or satellite
maneuverability could significantly broaden the scope of this technology. The
integration of MEMS technologies with electronics and optics is also being ex-
plored for chemical sensing, so-called lab-on-a-chip systems. Indeed, the current