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Palo Alto Research Center Creates the First Jet-Printed Plastic Transistor Arrays

Press release from the issuing company

PALO ALTO, Calif.--Oct. 28, 2003-- The Palo Alto Research Center (PARC) has developed the first plastic semiconductor transistor array entirely patterned using jet printing. Jet printing will lower the cost of active-matrix display backplanes by replacing vacuum deposition and photolithography in current manufacturing. The technology is also expected to open up new markets for wall-sized TVs, unbreakable cell phone displays, rollable displays, and electronic paper. "PARC contributed greatly to the amorphous silicon transistor that is at the heart of all active-matrix liquid crystal displays. With this breakthrough, PARC is well positioned to revolutionize display technology yet again," explained Mark Bernstein, president and center director of PARC. These arrays are printed using two techniques -- an additive and a subtractive method -- on either flexible or rigid substrates. Polymer inks are jetted directly onto substrates just where they are needed -- the additive process. Other materials are deposited everywhere and a mask is jet-printed on top. The material is then dissolved away except where protected by the printed mask -- the subtractive process. Both methods require precise layer-to-layer registration. The PARC printer is controlled by a patent-pending computer vision system to ensure proper alignment of the layers, even if the substrate warps or deforms during processing -- a well-known complication with flexible substrates. "The process is analogous to color registration. The printer correctly positions each layer of color with respect to the other layers, even if the paper or substrate has shrunk or warped. In this case, the layers to align are metal, dielectric and semiconductor, which create the transistor arrays," said Dr. Raj Apte, research scientist at PARC. The scientists at PARC perfected the technique of jet-printing polymer semiconductors to make high-performance transistor arrays. This advancement builds on the invention of polythiophene-based semiconducting polymer ink developed at the Xerox Research Centre of Canada (XRCC) by Dr. Beng Ong. It is one of several joint research projects conducted within the Xerox Innovation Group. As Dr. Bob Street, research fellow at PARC, described, "These printed transistors have exceptional performance for polymers and meet all the requirements for addressing displays: high mobility, low leakage and good stability." Under a National Institute of Standards and Technology grant, scientists from PARC and XRCC are collaborating with teams at Motorola Labs and Dow Chemical to "develop novel organic electronic materials and processing technologies to enable the fabrication of large-area electronic devices, such as displays, using relatively inexpensive printing technologies in lieu of semiconductor lithography."