Scientists beat circuit size limits

17 Jun 2002

A new technique to make smaller microelectronics circuits will also find use in the photonics industry.

Researchers at the University of Massachusetts have developed a one-step technique that deposits copper film within sub-100 nm channels, etched in silicon wafers (Science September 13).

James Watkins, assistant professor of chemical engineering, says that the technique, called chemical fluid deposition (CFD), has also been used to deposit films on semiconductor substrates for photonics applications.

"When we build devices for microelectronics, we have problems in placing the metal exactly where it is needed," Watson told optics.org. "However, our technique is ideal for filling narrow crevices in complex geometries."

"For photonics applications we have proven laboratory feasibility and want to get this technology to market as soon as possible," he added.

The research was fuelled by the semiconductor industry's drive to fabricate sub-100 nm copper interconnect structures by 2005. However, because today's gas and liquid deposition techniques cannot achieve this, Watkins and his colleagues decided to take a different approach.

Supercritical fluids possess gas and liquid properties, which Watkins says makes them ideal for fabricating tiny devices with complicated features: "The solution behaves more like a gas than a liquid and flows easily over complex surfaces and into narrow gaps."

To fabricate the copper interconnects the researchers used silicon substrates etched with sub-100 nm trenches. By chemically reducing supercritical solutions of copper compounds, films of the metal were successfully deposited in each trench.

The researchers, confident that CFD provides a better alternative to conventional deposition techniques, expect to commercialize the technique across microelectronics and photonics industries. Watkins says that the main barrier now is "to convince folks to do something different, which could take a few years."