Author: Endo, A.
Paper Title Page
FRA04 Optimization of High Average Power FEL Beam for EUV Lithography Application 990
 
  • A. Endo, K. Sakaue, M. Washio
    Waseda University, Tokyo, Japan
  • H. Mizoguchi
    Gigaphoton Inc, Hiratsuka, Kanagawa, Japan
  
  Ex­treme Ul­tra­vi­o­let Lith­o­g­ra­phy (EUVL) is re­al­ized with 100W plasma EUV source at 13.5nm. It is rec­om­mended by the EUVL com­mu­nity to eval­u­ate an al­ter­na­tive ap­proach based on high rep­e­ti­tion rate FEL, to avoid the power limit of the plasma source. Sev­eral pa­pers dis­cuss on the pos­si­bil­ity to re­al­ize su­per­con­duct­ing FEL to gen­er­ate mul­ti­ple kW 13.5nm light. We must no­tice that the pre­sent SASE FEL pulse has higher beam flu­ence than the re­sist ab­la­tion thresh­old*, and high spa­tial co­her­ence which re­sults in speckle pat­terns, and ran­dom lon­gi­tu­di­nal mode beat which leads to high peak powerμspikes. An ex­pand­ing mir­ror is in­stalled after the un­du­la­tor to re­duce the beam flu­ence, ex­ter­nal-seed­ing con­fig­u­ra­tion is em­ployed to re­duce the lon­gi­tu­di­nal mode beat, and total re­flec­tion beam ho­mog­e­nizer is used for spa­tial mode mix­ing. Pulse rep­e­ti­tion rate is more than 3MHz to can­cel the speckle pat­ter for­ma­tion by av­er­ag­ing il­lu­mi­na­tion. This paper dis­cusses on the low­est risk ap­proach to con­struct a pro­to­type to demon­strate a high av­er­age power 13.5nm FEL for the best op­ti­miza­tion in EUVL ap­pli­ca­tion, in­clud­ing the scal­ing to 6.7nm wave­length.
*J. Chalupský, L. Juha et.al, “Characteristics of focused soft X-ray free-electron laser beam determined by ablation of organic molecular solids”, OPTICS EXPRESS 15, 6036 (2007)
 		 
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