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Next generation EUV lithography is expected to be implemented by 2009 and the research investigation towards developing an optimized source, reliable collector mirror optics, mask cleaning and Line Edge Roughness (LER) has clearly drawn attention to many scientists and engineers around the globe. Center of Plasma Material Interaction (CPMI) at the University of Illinois at Urbana-Champaign is deeply involved in inventing and developing new techniques from a source-collector perspective. Ion fluxes and energies from Xe and Sn fueled EUV sources (DPP and LPP), which are on the verge of commercialization, are measured using in-house developed spherical sector analyzer (ESA). Efforts are underway to develop this system as a standardize debris diagnostic tool. Once the debris can be fully characterized, it will be possible to estimate the mirror lifetime, which is one of the greatest challenges towards Cost of Ownership (CoO). Known mirror lifetime can stimulate industry to incorporate mitigation schemes to improve the collector performance. Advanced mitigation techniques are developed and tested in Xtreme Technologies XTS 13-35 source at Illinois and shows great potential to alleviate the debris problem. It has been shown that adding 5% of a lighter gas to the fuel can reduce the ion energy and flux a factor of four while leaving the EUV output unchanged. An RF plasma in the pinch area and a pulsed foil trap in the line of sight of ESA are some mitigation schemes that are being investigated at present. Numerous investigations have been done at CPMI to study the collector behavior and cleaning technologies. The latest technique, RIE cleaning has the potential to be integrated in exposure tools where in-situ cleaning can be performed. This would drastically enhance the collector performance and lifetime, especially in the case of "off-normal" events. Sn removal techniques tested so far have managed to restore the reflectivity. New concepts, such as Gibssian Alloy as a collector mirror material is also suggested and testing is performed at elevated temperatures. Material characterization of post exposure samples shows that the segregating material is maintained on the surface despite erosion and acts to smooth the surface as well. |