Berggren teams to create self assembling copolymer circuits for microchips

March 16, 2010

MIT researchers coaxed tiny, chainlike molecules to arrange themselves into complex patterns, like this one, on a silicon chip. Previously, self-assembling molecules have required some kind of template on the chip surface — either a trench etched into the chip, or a pattern created through chemical modification. But the MIT technique instead uses sparse silicon “hitching posts.” The molecules attach themselves to the posts and spontaneously assume the desired patterns.  Image: Yeon Sik Jung and Joel Yang

Karl Berggren, the Emanuel E. Landsman Associate Professor of Electrical Engineering, has teamed with MIT Department of Materials Science and Engineering Professor Caroline Ross to create a more cost-effective way to use self-assembling techniques for microchip circuitry. Their work was reported yesterday in Nature Nanotechnology and today, March 16, 2010, in the MIT News Office by Larry Hardesty: "Self-assembling computer chips - Molecules that arrange themselves into predictable patterns on silicon chips could lead to microprocessors with much smaller circuit elements."

"The features on computer chips are getting so small that soon the process used to make them, which has hardly changed in the last 50 years, won’t work anymore. One of the alternatives that academic researchers have been exploring is to create tiny circuits using molecules that automatically arrange themselves into useful patterns. In a paper that appeared Monday in Nature Nanotechnology, MIT researchers have taken an important step toward making that approach practical.

Currently, chips are built up, layer by layer, through a process called photolithography. A layer of silicon, metal, or some other material is deposited on a chip and coated with a light-sensitive material, called a photoresist. Light shining through a kind of stencil — a “mask” — projects a detailed pattern onto the photoresist, which hardens where it’s exposed. The unhardened photoresist is washed away, and chemicals etch away the bare material underneath.

The problem is that chip features are now significantly smaller than the wavelength of the light used to make them. Manufacturers have developed various tricks to get light to produce patterns smaller than its own wavelength, but they won’t work at smaller scales."