Studies on Sn Thin Film Decomposition Using VHF hydrogen plasmas

Mengran JI, Ryo NAGATA, Keiichiro Uchiyama
One of the serious problems of EUV lithography is the accumulation of tin debris on the surface of the condenser mirror, which reduces the reflectance. This study investigated the possibility of using VHF hydrogen plasmas to decompose attached Sn debris. First, a simple VHF hydrogen plasma was generated, and the efficiency and characteristics of Sn removal with respect to hydrogen gas pressure, gas flow rate, and sample temperature were investigated. Regarding the gas pressure dependence of Sn
more » ... emoval, a Sn etching rate of 4.8 nm/min was obtained at 35 Pa. This was more than twice as large as the value previously reported using a RF hydrogen plasma. Furthermore, as a result of combining the hollow cathode discharge, which has an electron confinement effect, with the VHF discharge, the electron density was more than doubled. For this case, the maximum Sn etching rate of 8.3 nm/min was obtained.
doi:10.15017/4479147 fatcat:qcswemshebfklhylwmjapxfbcm