成果報告書詳細
管理番号20150000000362
タイトル*平成24年度中間年報 「新エネルギーベンチャー技術革新事業 新エネルギーベンチャー技術革新事業(太陽光発電) ダメージフリーを達成するシリコンのエッチング援用マルチスライシング技術の開発」
公開日2015/7/17
報告書年度2012 - 2012
委託先名株式会社クリスタル光学 学校法人立命館
プロジェクト番号P10020
部署名イノベーション推進部
和文要約
英文要約Title: New Energy Venture Business Technology Innovation Program/New Energy Venture Business Technology Innovation Program (photovoltaic power generation)/ Development of a damage free multi-slicing method of silicon utilizing a wet chemical etching (FY2012-FY2013) FY2012 Annual Report

Si wafers for solar cells are fabricated by slicing Si ingot using diamond multi-wire saw. Diamond-wire slicing can achieve high removal rate, however, the method generates mechanical damages on the sliced Si surface because the Si surface is abraded high hardness abrasives (diamond). Such mechanical damages are generally removed by wet etching because the damage deteriorates the performance of photovoltaic devices. Recently, the slicing method without generating mechanical damage on Si surface is strongly required because of the increasing demand of ultra-thin Si wafers with a low sliced kerf width. Therefore, we have developed a novel Si slicing method using a wet chemical etching. In this method, Si ingot is frictioned by a running wire in etching solution containing HNO3 and HF mixture solution. The etching rate of Si is accelerated at the contact point between the Si ingot and the wire by the tribological reaction. Compared with conventional mechanical slicing methods, the proposed slicing method can achieve lower kerf loss and thinner Si wafer thickness without generating the mechanical damage on the wafer surface, because the proposed method is based on chemical reaction and uses no abrasives. In this project, the slicing characteristics of the proposed slicing method containing removal rate of ingot and kerf loss were investigated with different slicing conditions. The wires used in this process were Ni-Cr alloy and stainless steel wires, because they showed high corrosive resistance to a HNO3 and HF mixture solution. The removal rate was increased with increasing the wire running speed. The achieved highest removal rate was 120 micro-m/min. The sliced kerf loss can be reduced by optimizing the composition of etchant. The extremely low kerf loss less than 60 micro-m is achieved by the proposed method. The optical microscopy and scanning electron microscopy images exhibit that the Si surface sliced by the proposed method has no mechanical damages, while many mechanical fractures can be observed on the surface sliced by diamond wire sawing. Furthermore, Raman spectroscopy shows that the sliced wafer surface contains a crystalline Si. On the other hand, the diamond wire sawing generates the amorphous Si layer on the sliced surface. Finally, the surface roughness of sliced surface was investigated using optical interferometer. It was found that the proposed method can produce the Si surface with a roughness of approximately 0.3 micro-m Ra, which is equivalent to those of diamond wire sawing.
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