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

Published: January 2008

Glossary

amplifier: A device that enlarges and strengthens a signal's output without significantly distorting its original waveshape. There are amplifiers for acoustical, optical and electronic signals.
beam: 1. A bundle of light rays that may be parallel, converging or diverging. 2. A concentrated, unidirectional stream of particles. 3. A concentrated, unidirectional flow of electromagnetic waves.
extreme ultraviolet: Extreme ultraviolet (EUV) refers to a specific range of electromagnetic radiation in the ultraviolet part of the spectrum. EUV radiation has wavelengths between 10 and 124 nanometers, which corresponds to frequencies in the range of approximately 2.5 petahertz to 30 exahertz. This range is shorter in wavelength and higher in frequency compared to the far-ultraviolet and vacuum ultraviolet regions. Key points about EUV include: Source: EUV radiation is produced by extremely hot and energized...
light: Electromagnetic radiation detectable by the eye, ranging in wavelength from about 400 to 750 nm. In photonic applications light can be considered to cover the nonvisible portion of the spectrum which includes the ultraviolet and the infrared.
nano: An SI prefix meaning one billionth (10-9). Nano can also be used to indicate the study of atoms, molecules and other structures and particles on the nanometer scale. Nano-optics (also referred to as nanophotonics), for example, is the study of how light and light-matter interactions behave on the nanometer scale. See nanophotonics.
nanotechnology: The use of atoms, molecules and molecular-scale structures to enhance existing technology and develop new materials and devices. The goal of this technology is to manipulate atomic and molecular particles to create devices that are thousands of times smaller and faster than those of the current microtechnologies.
photonics: The technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon. The science includes light emission, transmission, deflection, amplification and detection by optical components and instruments, lasers and other light sources, fiber optics, electro-optical instrumentation, related hardware and electronics, and sophisticated systems. The range of applications of photonics extends from energy generation to detection to communications and...
plasma: A gas made up of electrons and ions.
seed: 1. In glass, a solid inclusion having a small diameter. 2. A particular, single crystal that, after undergoing the Czochralski method, evolves into large single crystals.
wavelength: Electromagnetic energy is transmitted in the form of a sinusoidal wave. The wavelength is the physical distance covered by one cycle of this wave; it is inversely proportional to frequency.

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