Xenon re-circulation systems for next generation lithography tools

摘要

Next generation lithography tools designed to pattern critical dimensions at < 45 nm will require extreme ultraviolet (EUV) light sources. Xenon is currently a strong candidate for the source medium for production of EUV light at 13.5 nm. A consistent supply of ultra high purity xenon is required for efficient light source production. Several factors must be considered in the overall operating costs of the EUV tool. 1. The high cost of xenon (typically ～$4/litre). 2. The quantities required for EUV source production, which are typically: 2.1 4slpm for Laser Produced Plasma (LPP) 2.2 300sccm for Gas Discharge Produced Plasma (GDPP) On the basis of these figures: 3. The annual xenon cost would typically be approximately: 3.1 $HM/year for LPP, 3.2 $ IM/year for GDPP, and 4. Recycling of xenon offers a significant operating cost reduction. This type of re-circulation system is not restricted to high xenon throughput applications, but can be scaled in size, and hence cost, for application to lower throughput process applications. Additional applications in mainstream silicon processing including a new development in Dielectric Etch using xenon could also benefit from re-circulation. Present research indicates that for a typical recipe, 675sccm xenon is required per wafer pass, this equates to an annual cost of $0.6M. BOC Edwards has designed & built a series of five fully integrated xenon re-circulation systems for lithography applications. Each system has been custom designed to exact application requirements, including liquid/solid xenon filament production. Additionally, an important footprint reduction has been achieved during the design evolution, which ideally suits dielectric etch applications.