EUV Laser Light Improved

The quality of laser light at extremely short wavelengths has been improved dramatically, a discovery that could prove valuable to the semiconductor industry as it aims to develop faster, light-based computer chips.

The discovery covers wavelengths of light near 13 nanometers (nm), or billionths of a meter (a human hair is about 60,000 nm). These wavelengths are particularly valuable for the semiconductor manufacturing industry, which aims to develop next-generation computer chips by 2010 or 2011 that use that type of light, said Jorge Rocca, a professor of physics and of electrical and computer engineering at Colorado State University (CSU). He and colleagues Yong Wang, Brad Luther, Francesco Pedacci, Mark Berrill, Eduardo Granados and David Alessi collaborated on a research paper published online this week by Nature Photonics.

The technology involves the generation of short wavelength light in the extreme ultraviolet (EUV) or soft x-ray range of the electromagnetic spectrum with wavelengths about 50 times shorter than visible light. These lasers can be used to "see" tiny features, create extremely small patterns and manipulate materials in ways that visible light can't.

"The potential applications are many -- ultrahigh resolution microscopy, patterning to make nanodevices, and semiconductor industry measurements," said Rocca, senior author of the paper. "There are many other possibilities that in the future will also include biology."

Brad Luther (left) and Yong Wang of Colorado State University work on an ultrashort laser system used to develop x-ray laser schemes in Jorge Rocca’s extreme ultraviolet laser lab. (Photo courtesy CSU)

The research focused on making the light of lasers operating at 18.9 and 13.9 nm more "coherent" -- a property that distinguishes laser light from light generated by other sources. Rocca's team generated a little seed of coherent x-ray light, converted the frequency of a visible laser beam to soft x-ray light and obtained a very coherent light at a low intensity. That seed was injected through a plasma amplifier and grew to produce a very high intensity beam of soft x-ray light with extraordinarily high coherence.

"Coherent soft x-ray light can be used to measure the properties of materials and directly write patterns with nanoscale dimension," Rocca said. "It can be used to look for extremely small defects in the masks that will be used to print the future generations of semiconductor chips."

The work is part of the research conducted at the National Science Foundation's Center for Extreme Ultraviolet Science and Technology -- a partnership between CSU in Fort Collins, the University of Colorado-Boulder and the University of California Berkeley -- to develop compact extreme ultraviolet coherent light sources, optics and optical systems for nanoscience, nanotechnology and other applications.

For more information, visit: www.colostate.edu