INDUSTRY NEWS

Rubber-stamp technique touted as flexible and low-cost photolithography alternative

Anew rubber-stamp technique could present an economical alternative to conventional lithography, according to the researchers at Lucent Technologies, where they developed the technique.

Using rubber stamps with features as small as 0.2 µm, researchers at Lucent's Bell Labs in Murray Hill, NJ, have stamped submicron features on glass, plastics, metals, and other materials. The reusable stamps have been used to make high-performance optical and electronic devices, including plastic transistors.

"The research has potential applications in niche semiconductor areas where photolithography does not work as well, such as plastic electronics," says Steve Eisenberg, media relations manager for Bell Labs.

To make the stamps, researchers pour liquid rubber onto a prototype made of patterned silicon. Once the rubber solidifies, it is peeled off the silicon to create an exact reproduction of the silicon relief pattern. John Rogers, a Bell Labs chemist, says the technique can print features on rough or curved surfaces and on other materials incompatible with traditional lithography, giving it potential for use in novel applications.

Rogers and his colleagues created working plastic transistors with 0.2-µm features. The stamp they used to do this was a precise replica of a patterned silicon wafer. Spreading organic ink on the stamp, the scientists pressed the stamp on a gold-coated plastic film and etched off the nonimprinted area of the gold to leave patterns of high-resolution circuits. The ink protected the gold from the etch step. They then stripped away the ink with UV light to expose the underlying gold layer. Finally, they deposited organic semiconductor material on the gold pattern.

The scientists also made resonators for plastic-based lasers for use in optical communications. They used a flat rubber stamp with a series of raised 0.3-µm lines to set lines of gold on plastic. Etching removed the areas not protected by the gold to create surface-relief resonator structures conforming to the pattern.

"These lasers had operating characteristics that were nearly identical to those produced by lasers manufactured with high-resolution photolithography," Rogers says.

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