Center for NanoTechnology to push lithography below 35 nanometers

McFarland-Bascom Professor Franco Cerrina (32K JPG)

Using a one nanometer X-ray wavelength and masks fabricated onto diamond membranes, the Center for NanoTechnology and Mitsubishi Electric will develop lithography technology to take the semiconductor industry four generations into the future. McFarland-Bascom Professor of Electrical and Computer Engineering Franco Cerrina says a three-year, $4.2 million dollar grant from the Defense Advanced Research Projects Agency (DARPA) will help the Center for NanoTechnology acquire new equipment, modify existing tools and develop new processes to extend lithography below 35 nanometers.

Currently, the semiconductor industry uses an ultraviolet light wavelength of 248 and 193 nanometers to pattern transistors as small as 130 to 150 nanometers, says Cerrina. But to push fabrication below 100 nanometers, researchers need new technical solutions. For example, at shorter wavelengths lenses intended to focus the circuit pattern on the silicon, absorb much of the light. Overcoming these obstacles dramatically increases the complexity and costs of nanometer-scale device fabrication systems.

Working with X-rays, Center for NanoTechnology researchers developed much simpler solutions using lithographic techniques on the order of 70 to 80 nanometers. The DARPA grant will help the center push the limits of lithography to 50, 35 and ultimately 20 nanometers.

"The region past 35 nanometers is well beyond the technology roadmap of the semiconductor industry," says Cerrina. "We call the move below 50 nanometers 'X-ray phase two' because we're using a new set of mask materials and systems. Previously we used a silicon-carbide base material. Now we will develop new photochemistry and will use two to five-micron-thick diamond membranes. The new diamond masks are much more rigid and will help to eliminate some of the problems that plagued earlier versions of X-ray lithography."

Mitsubishi Electric will supply the diamond membranes and develop the masks. Cerrina's team will modify an existing X-ray beamline and develop the exposure system together with Suss Advanced Lithography (SAL). "Our facility has one of the only synchrotrons with the proper characteristics to carry out this research," says Cerrina. "It's an excellent collaboration."

Cerrina says funding will provide important upgrades to the center's equipment including a new high-resolution scanning electron microscope and a new atomic force microscope.