MIT building self-assembling computer chips

[begood]

In the journal Nature Nanotechnology this week, the researchers describe a process that could become an alternative to conventional photolithography, which relies on light projected onto a photo-sensitive material, as people continue to forecast the demise of Moore's Law. That observation states that the number of transistors that can be placed on an integrated circuit doubles roughly every two years.

Led by Caroline Ross and Karl Berggren, both engineering professors, the scientists used electron beam lithography to create nanoscale "posts" on a silicon chip. They then deposited copolymers--large molecules of two polymers with repeating structural units--on the chip. The copolymers spontaneously linked to the posts and arranged themselves into useful patterns.

The polymers naturally want to separate from each other, thus causing them to arrange in predictable ways. (Berggren compares compares different polymer molecules to the characters played by Robert De Niro and Charles Grodin in "Midnight Run"--a bounty hunter and a white-collar criminal who are handcuffed together but can't stand each other.)

A variety of patterns that can be used in circuit design could be achieved by changing the shape and position of the posts, the proportions of the polymers, and the length of the molecule chains, MIT said.

When exposed to plasma, one polymer burns away, while the other turns to glass. The latter could work like a photoresist in optical lithography (a photoresist is a light-sensitive material onto which light is projected to form a pattern for the chip).

The team is still working to produce functioning circuits in a prototype chip, and to create even smaller chip features with the copolymer technique.

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