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Printed electronics: Next step beyond silicon ICs

Posted: 22 Nov 2007     Print Version  Bookmark and Share

Keywords:printed electronics  TFT circuit  RFID tag 

Developers of TFT circuits recently claimed breakthroughs that may finally push the technology to market and enable the long-promised low-cost class of electronic paper, displays, labels, RFID tags, sensors, smart cards and perhaps even programmable wallpaper.

For years, promoters have been billing TFT circuits—and the broader category of printed or plastic electronics—as the next step beyond wafer-based ICs. The technology uses inkjet printers and polymer inks to print cheap, low-density ICs on a system, display or just about anything else. As such, it promises to make the IC ubiquitous, opening a host of new applications.

However, despite the millions of dollars that have been invested in R&D over the years, a number of companies—including Intel Corp.—have failed to move TFT circuits into production. The transistors are working in the lab, but not one company has "sold anything" in the commercial market thus far, said Peter Harrop, chairman of consulting firm IDTechEx Ltd.

Emerging market
At the Printed Electronics USA event, 3T Technologies, Kovio, Orfid, PolyIC, STMicroelectronics (ST), Thin Film Electronics AB and other concerns tipped details on printed electronics for a range of applications. Vendors claimed to have solved many of the problems associated with the technology, including lackluster transistor performance, poor mobility and integration issues for the polymer materials.

More than 150 organisations are scrambling to develop the technology in one form or another. Many seek shares of a TFT and memory market that IDTechEx predicts will grow from nearly zero today to Rs.158.20 crore ($40 million) by 2009 and Rs.31,639.87 crore ($8 billion) by 2017.

The broader printed-electronics market, according to IDTechEx, includes conductive inks, electrophoretic displays, OLEDs, thin-film photovoltaics, and transistor circuits and memories. In total, the market for printed electronics, including organics, inorganics and composites, is projected to grow from Rs.7,118.97 crore ($1.8 billion) in 2007 to Rs.190,551.13 crore ($48.18 billion) by 2017, according to IDTechEx.

The fastest-growing market segments are for TFT and memory, according to the firm. Unlike traditional silicon chips, TFT circuits do not use crystalline or amorphous silicon; instead, thin-film products are based on organic or inorganic compounds that enable flexible circuits.

"The transistors are the key to huge new markets that the silicon chip will never reach," Harrop wrote in a recent report. "The new transistors can be deposited on low-cost flexible substrates, aluminum or stainless-steel foil. [At present] they are much larger than today's silicon transistors, but they can be one-hundredth of the cost, thinner and lighter in weight."

Birth of new apps
Thin Film Electronics, which produces low-cost, all-polymer nonvolatile rewritable memories, is also pursuing RFID tags, smart labels and other applications. It's highly unlikely that TFT will replace today's semiconductor memories, said Rolf Aberg, an executive board member of Thin Film Electronics. "It will be a complementary technology to semiconductors," he told EE Times. "We think it will open up new applications."

For example, Belgium's Cartamundi Group plans to use Thin Film Electronics' technology to deposit memory circuits on a new class of standalone game cards that would let users play games over the Internet.

Thin Film is putting the manufacturing infrastructure in place to bring its technology to market. Agfa and Thin Film announced that they intend to enhance the materials for volume production of printed memory devices. Thin Film also signed a deal with InkTec Co. Ltd of South Korea to collaborate on optimising the latter's silver inks for Thin Film's memory cell electrodes.

Meanwhile, ST claimed to have developed the first entries in a line of standalone thin-film circuits. Using a combination of nanoimprint lithography and inkjet printers, the company has devised a 4bit arithmetic logic unit, a full adder and a one-time-programmable device, said Luigi Occhipinti, corporate R&D program manager for ST.

Occhipinti acknowledged that there are a number of hurdles to clear before the technology enters production. Besides lackluster transistor performance, he cited "a lack of stability in n-type organic materials" in a conference presentation.

As a result, the first applications in thin-film circuits may not be standalone devices, but offerings in the booming area of RFID.

Startup Kovio Inc. came out of stealth mode with a silicon-based TFT technology—a low-cost RFID tag. While present RFID tags run Rs.5.93 (15 cents) per unit, Kovio CEO Amir Mashkoori said its technology will lower the cost of RFID tags to Rs.1.98 (5 cents) when it moves into production in 2008. The ultimate goal is to bring the tags down to a penny per unit.

Meanwhile, PolyIC GmbH & Co. KG claimed it had beaten rival Kovio to the punch. PolyIC is developing thin-film devices manufactured in an industrial roll-to-roll printing process. The company touts two organic-based chips: PolyID, a 13.56MHz device equipped with a 4bit memory, and PolyLogo, geared for "smart objects."

The first products are expected to sample by year's end, said Wolfgang Clemens, head of applications at PolyIC. He would not specify pricing for the company's RFID tags but said the goal is to drive costs to the "few-cent range."

Tapping on displays
Another emerging market for the technology is displays. Startup Orfid Corp. claims to have begun shipping its first devices for the display market. Orfid has developed an organic electronic technology called the vertical organic field-effect transistor (VOFET). With its architecture and the use of conductive polymers in its fabrication, the VOFET offers performance characteristics similar to conventional, wafer-based silicon transistors but can be produced at significantly lower cost, the company said.

U.K. startup 3T Technologies Ltd, on the other hand, is working on a generic device platform and process for applying transparent conductive oxide materials to enable what it calls "transparent thin-film technology" or "invisible circuitry."

"Based initially on zinc oxide as the active transparent semiconductor, the device construction and manufacturing approach provide the basic building block for transparent logic circuitry and display pixel switching to support a wide range of display media," according to the company.

- Mark LaPedus
EE Times

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