EUV conference addresses challenges

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The four-day 2012 International Symposium on Extreme Ultraviolet Lithography, hosted in Brussels by Imec in cooperation with Sematech and Eidec, addressed the critical issues facing EUV technology. Industry and research experts named the timely development of a source suited for high-volume manufacturing as the most critical issue. Other challenges remain the development of yielding masks and the further development of high-quality EUV resists.

There was a consensus among the experts that the productivity of the EUV source will have to increase dramatically over the next 1-2 years to enable the introduction of EUV lithography into high-volume manufacturing. By 2014, a reliable 200W source is needed to support the first cost-effective production. After that, the source power will have to be further augmented to 500-1000W to allow for long-term cost-effective manufacturing continuing IC scaling according to Moore’s law.

An encouraging development in the past 12 months is that the reliability of the available sources has improved, which is speeding up learning and development in the pilot lines today. Another plus was that researchers have demonstrated ways to increase the conversion efficiency to the 4-5 per cent range, which is significantly higher than what has been achieved to date.

There has been a clear progress in EUV mask handling. Nevertheless, the availability of yielding masks to support the pilot lines and the start of high-volume production remains a serious concern. As a result, EUV pellicle solutions are being explored again, to help mitigate the defect challenge. Speakers at the symposium also reported on incremental improvements in resists that meet the requirements of resolution, line width roughness, and sensitivity simultaneously. One issue is that the best-performing resist materials often show a lower photo speed that does not align with the sensitivity assumed in the productivity roadmap of the exposure tool suppliers.

As a conclusion from this symposium, there has been a steady progress in all areas, but the industry still has to resolve a number of significant challenges before EUV lithography can be introduced in high-volume manufacturing, which is now expected to happen as of 2014.