Researchers Enhance Lithography Light Sources

Tag : EL Light

In an effort to help create faster, better and cheaper lightsources for chips, UC San Diego researchers, in collaboration withCymer, Inc., are developing laser-produced light sources for nextgeneration Extreme Ultraviolet Lithography (EUVL).
The researchers, led by mechanical and aerospace engineeringscientist Mark Tillack, filed a patent in May 2008 for their latestdiscovery indicating that longer pulse lengths can provide similarperformance as short pulse lengths. Tillack and his team foundthat employing a long pulse in a CO 2 laser system used in an EUVL source could make the systemsignificantly more efficient, simpler, and cheaper compared to thatusing a shorter pulse. Their research findings were recentlypublished in Applied Physics Letters.
Today’s semiconductor companies are diligently working ondeveloping EUVL as the leading candidate for next generationlithography tools to produce microchips with features of 32nanometers or less. While great progress has been made in thisfield, several challenges still exist to cost effectively fieldEUVL in high volume manufacturing. Nowadays, the light source insemiconductor lithography is applied directly from a laser througha mask to a wafer. In EUVL, a laser is used to produce extremeultraviolet light that is sent to a mask and then the wafer. Thisindirect process is more inefficient, and could require a verylarge and very expensive laser source, Tillack said.
“CO 2 lasers, which we use in our lab, have two advantages – theyare inherently cheaper to build and operate, and they give betterconversion efficiency from the laser to EUV light,” he said. “Our discovery that long pulses work well enough means thatthe CO 2 laser system can be built and operated more cheaply.”
Tillack pointed to possible future applications for EUVL, such asflash memory chips, which will become denser and denser. “Imagine in the future being able to make a 200 gigabyteflash disk memory stick cheaply,” he said. “EUVL couldmake hard disks obsolete”.
“We didn’t know how to make a powerful source of lightin this part of the spectrum before,” added Tillack, also anassociate director of the UC San Diego Jacobs School ofEngineering’s Center for Energy Research. “We might beopening new avenues for advanced light sources. We need tocontinue our research and begin to look at other possibleapplications.”
Tillack's EUVL work was supported by Cymer Inc. and by theUniversity of California under the UC Industry-UniversityCooperative Research Program.