SEMATECH: LPP gaining favor as EUV source

May 21, 2007 – Laser-produced plasma sources, once seen as a “dark horse” technology for extreme-ultraviolet (EUV) lithography, seem to be gaining steam as the most promising power source for the future litho equipment, according to SEMATECH, citing feedback from a recent workshop.

LPP sources using tin as fuel now produce up to 130W bursts of power, extrapolated to >40W of power at intermediate focus using collectors, according to presenters at the EUV Source Workshop held earlier this month in Baltimore, SEMATECH noted. That could be enough to meet the low end of minimum requirements for beta-level EUV scanners slated for delivery in 2009. Vivek Bakshi, workshop chair and senior member of technical staff at SEMATECH, noted that the reported power stats come from suppliers’ estimates of the performance of their own in-house prototypes.

LPP-based EUV tools bombard a sliver of tin with a high-powered laser to produce light, which is gathered into mirrors and focused as a beam into the EUV tool to produce the chip patterns. SEMATECH notes that discharge-produced plasma (DPP) sources, currently being used in alpha EUV tools, do generate more power, consume less energy, and cost less, but also face significant heat and debris problems.

Among findings presented at the workshop were data regarding several LPP-based approaches (e.g. pulsed CO2, Nd:YAG, and fiber-based lasers), which show some promise though still falling well short of power requirements for commercial EUV use. “Multiplexing” less powerful systems can reach those marks, and work is being done to reduce the number of modules needed in such a configuration, noted Bakshi.

In other discussions at the workshop, a panel discussed the challenges of developing a source collector module (SoCoMo), incorporating an EUV source, debris mitigation devices, spectral purity filters, and collector mirrors to channel clean EUV photons to a EUV scanner. There was agreement that future EUV devices likely will come from suppliers with an optimized SoCoMo developed with scanner manufacturers, but tight collaboration among all parties (source, collector, scanner makers, researchers, and end users) will be required to demo EUV beta tools with 40-60W power at intermediate focus and sustained reliability by late 2008, to be ready for installation in beta EUV tools the following year, noted Stefan Wurm, SEMATECH’s EUV strategy program manager.


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