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Microelectronics Technology Alert reports on the latest advances in the broad
range of technology related to microelectronic devices. Topics regularly
presented range from the manufacture of CPUs and RAM chips to data storage to
the emerging field of optoelectronic computing and communication. Special
emphasis is given to semiconductor materials, displays, photonics, and novel
approaches to chip design. Beyond reporting on the latest technology,
Microelectronics Technology Alert keeps you abreast of the latest R&D
developments at major corporate and academic research centers assisting you in
monitoring your competitors and creating strategic alliances.
Sample Briefing
TEST CHIPS FAST AND CHEAP
A new way to use a laser pulse, developed at MIT, gives you a quicker, easier
and cheaper way to test computer chips. The research team thinks it will save
the microelectronics industry millions of dollars. And, looking further in the
future, the laser pulse technology could lead to a way to optically switch
materials from one phase to another. Or it could provide an early warning signal
for eye disease.
The chemists at MIT's Materials Processing Center have been studying how
materials respond when irradiated by pulsed laser light. They are learning how
light, particularly short pulses, interacts with matter and how to exploit these
interactions. Applications will range from basic knowledge about complex
materials to devices.
The chip test uses the laser pulse to analyze the thin films used in
microelectronics components. It shows up variations in the thickness of the
metal layers, a major cause of device failure and low microelectronics
manufacturing yield. Copper, tungsten, and other metal layers on the silicon
base have precisely specified thicknesses ranging from 100 angstroms to 10,000
angstroms. Tests to insure that each film layer is the right thickness and is
properly stuck to the layer below are costly and destroy the sample.
The MIT noncontact optical test is nondestructive, uses a briefcase-sized laser
device, and can measure film thickness to within 1-3 angstroms, a single layer
of atoms. At the same time, adhesion is checked.
Short pulses from the minilaser generate ultrasonic waves in the thin film.
Light from a second laser monitors the acoustic waves and determines their
velocity, which depends on the thickness and adhesion of the film. Difficult
adjustments are not required and the machine is easy to use. Comparing the
signal from a sample on the production line to that from a perfect component
shows if the production sample is flawed. Other thin films could also be tested:
optical elements, liquid crystal displays, and ultrahard coatings. Polymer
films, including biopolymers such as the cornea of the eye, can also be
examined. The sample simply must be smooth and reflective enough to bounce back
light without too much scatter.
Experiments have begun on using the ultrashort laser pulses to optically control
the structure of crystalline solids by moving atoms from their initial positions
along selected microscopic pathways towards a new position. Getting this under
enough control to be useful is still far off, but the goal is to optically
switch a material from one structure to another without any absorption of the
light. An ice crystal, for example, can assume nine different forms and other
crystals may be altered by rearranging their structures from one phase to
another. This way you could optically control a material by changing the
configuration of its molecular infrastructure. You might even create new states
of existing materials by forcing their atoms into configurations they wouldn't
normally assume.
So far, the MIT group has shaped a pulse of light less than one femtosecond long
into a timed sequence of pulses that can launch vibrational waves in a crystal
that come with larger and larger amplitudes. The pulses of light push at the
crystal lattice framework, causing ever-larger excursions from the original
position. Get a big enough motion going and the material could enter a new
crystalline phase.
The group has also shaped a single light pulse into many pulse sequences that
can reach different regions of a sample. This gives another way to manipulate
and amplify the vibrational wave as it travels through the crystal.
Looking at the more down-to-earth chip testing application, MIT's Lincoln
Laboratory has developed the pulsing device into a very small mini laser. This
has been developed commercially by a start-up formed by the original
researchers, chemistry professor Keith Nelson and two grad students. The company
has been acquired by Philips Analytical N.V. | 
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