Light Source Enables UV Lithography

Aaron J. Hand

As circuit features shrink and optical lithography approaches its technical limits, the world's semiconductor industry continues to evaluate its options for the chip-making method of the future. Extreme-UV lithography -- which should be able to create circuit linewidths as small as 100 nm and perhaps down to 50 nm -- is one option being considered.

The University of Central Florida's extreme-UV light source should be smaller, simpler and cheaper than existing options.

Now researchers at the University of Central Florida's Center for Research and Education in Optics and Lasers are developing a new light source for the job.

The current frontrunner as the extreme-UV light source is a laser-produced plasma developed at Sandia National Laboratories, according to professor William Silfvast. He leads the university's extreme-UV lithography research but currently is on sabbatical at Sandia in Livermore, Calif. Silfvast's new light source, still under development, promises to be much cheaper, much more efficient and more compact than its predecessors, he said.

The discharge device is about the size of a person's thumb. Packaged with the required electronics, it is about the size of a small filing cabinet, Silfvast said. So far the researchers have found lithium vapor and xenon gas, both of which are good radiators, to be the best materials for the light source, which operates best at 11.4 and 13.5 nm.

The Central Florida team is working with Sandia to develop engineering prototypes. It also is getting support from the Semiconductor Research Corp., a US consortium of semiconductor manufacturers, and the Extreme Ultraviolet Limited Liability Corp., a private industry consortium led by chipmakers Intel, Motorola and Advanced Micro Devices.

Extreme-UV lithography is not expected to be adopted for at least five years, at which point his light source should be ready as well, Silfvast said. But even if the semiconductor industry decides to adopt an ion-beam, electron-beam or x-ray technology over extreme-UV lithography, the new light source could be used for microscopes or other inspection tools, he added.

"What's happened in the development of extreme-UV lithography is that it's made advances in the technology," he said. "Having sources that are compact are a key element in any advancement in optics."