by Ed Korczynski, Senior Technical Editor, Solid State Technology
May 14, 2008 – The highlight of the April 16 North California Chapter of the American Vacuum Society’s (NCCAVS) Thin-Film Users Group (TFUG) meeting on printable electronics was the detailed technology presentation on self-aligned imprint lithography (SAIL) as developed by HP and PowerFilm Solar for their roll-to-roll (R2R) IC line. Many other companies are also developing real ultra-low-cost ICs and sensors using micron-scale printed thin-film transistors (TFT).
Palo Alto Research Center, Inc. (PARC, now independent from Xerox) working with Stanford University and Cabot Microelectronics recently won a DARPA contact to develop light-weight, inexpensive sensors using printing technologies. The basic technology uses printed TFT materials with all processing done at <200°C to allow for compatibility with plastic substrates, and should be applicable to the monitoring of pressure, acceleration, temperature, and chemical exposure.
PARC’s Ana Cladia Arias discussed methods used to deposit and integrate solution-processed materials using ink-jet printing. They have developed a complete additive process for the fabrication of simple prototype TFT backplanes on glass and on flexible plastic substrates. Surface energy control of the polymer gate dielectric layer allows printing of the metal source-drain contacts with gaps as small as 10μm. Silver nanoparticles are used in the ink that forms gate and data metals. The ION /IOFF ratio is ~105, and TFT mobility of 0.05 cm2/V