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EUVL exposure tools for more than 100-wafer∕h throughput require highly efficient sources of EUV radiation. It is commonly accepted that the development of suitable EUV sources is one main risk factor in bringing this promising technology to a cost-effective implementation in high-volume semiconductor manufacturing fabs. While investing enormous efforts in developing such sources, it has become obvious that the requirement can be met only if these sources operate close to the physical limits and the limits of thermal engineering.
Several types of LPPs and DPPs are under investigation by several groups as EUV sources for the first EUV exposure tools. Within the last three years such sources have demonstrated improvements of several orders of magnitude with respect to relevant parameters such as power and component lifetime. On looking at the present performance of EUV sources with up to 2% radiator efficiency into 2πsr, repetition rates of up to 10 kHz, input powers beyond 20 kW, and component lifetimes on the order of more than 1010 pulses, the development of EUV sources that can meet the performance specifications seems feasible, if only this pace of progress can be sustained.
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