5.最近のトピックス : 5.2フッ素,塩素負イオン生成とSi,SiO_2とのエッチング反応 : 負イオンを見直そう(<特集>負イオン特集)

概要

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In order to neutralize positive charge built in high aspect ratio gaps and holes, a new etching method was studied employing alternate irradiation of positive ions and negative ions which were extracted from downstream plasma of SF_6 or Cl_2. As compared with easy generation of fluorine negative ions, chlorine negative ions were difficult to be produced even at high pressure and remote distance from a C12 plasma region. Thus, plasma space potential ( Vs) became negative in the case of SF_6 plasma, while Vs remained still positive in the case of Cl_2. However, values of Vs were limited to be less than 50 volt near a electrode biased to + 50 volt for increasing electrode area. Si etching characteristics carried out under positive and negative DC biasing demonstrated that Si etch rates by positive biasing were faster than those by negative biasing. In advance, SiO_2 and Ba (Sr) TiO_3 Were etched rapidly by using the condition including negative ions in contrast with slower etching with positive ions alone. This is likely due to a reduction reaction effect of negative ions. But more efforts should be made for making the effect clear.
社団法人プラズマ・核融合学会の論文
1996-11-25