Light Colors Shrink Chips

Two separate colors of light have been used to reduce the size of circuitry in nanotechnology devices such as computer chips and solar cells.

As with current methods in the nanoengineering field, one color of light inscribes a pattern on a substrate, said University of Colorado at Boulder assistant professor Robert McLeod of the electrical, computer and energy engineering department. But the new system developed by McLeod’s team uses a second color to “erase” the edges of the pattern, resulting in much smaller structures.

The team used tightly focused beams of blue light to record lines and dots thousands of times smaller than the width of a human hair into patterned lithography on a substrate, McLeod said. The researchers then “chopped off the edges” of the lines using a halo of ultraviolet light, trimming the width of the lines significantly.

“We are essentially drawing a line with a marker on a nanotechnology scale and then erasing its edges,” he said. The method offers potential new approaches in the search for ways to shrink transistor circuitry, a process that drives the global electronic market that is pursuing smaller, more powerful microchips, he added.

McLeod and his team used a tabletop laser to project tightly focused beams of visible blue light onto liquid molecules known as monomers. A chemical reaction initiated a bonding of the monomers into a plasticlike polymer solid, he said. If the beam was focused in one place, it inscribed a small solid dot. If the beam was moving the focus through the material, it created a thin thread, or line.

The researchers then added a second ultraviolet laser focused into a halo, or doughnut, which surrounded the blue light. The special monomer formulation was designed to be inhibited by the UV light, shutting down its transformation from a liquid to a solid, he said. This “halo of inhibition” prevented the edges of the spot or line from developing, resulting in a much finer final structure.

The process may help extend the life of Moore’s law, a trend described by Intel co-founder George Moore in 1965, which predicted that the number of transistors that can be placed on a single integrated circuit doubles about every 18 months.

The new technology has the potential to lead to the construction of a variety of nanotechnology devices, including “nanomotors,” McLeod said. “We now have a set of new tools. We believe this is a new way to do nanotechnology.”

A paper on the research was published in the April 10 issue of Science Express, the online version of Science magazine. CU-Boulder co-authors included Timothy Scott and Christopher Bowman of the chemical and biological engineering department and graduate students Benjamin Kowalski and Amy Sullivan of the electrical, computer and energy engineering department. Sullivan is now a professor at Agnes Scott College in Decatur, Ga.

The research effort was funded by the National Science Foundation and through the University of Colorado Innovative Seed Program. A preliminary patent based on the technology has been filed by the CU-Boulder research team.

For more information, visit: www.colorado.edu