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Effect of Saw-Damage Etching Conditions on Flexural Strength in Si Wafers for Silicon Solar Cells

태양전지용 실리콘 기판의 절삭손상 식각 조건에 의한 곡강도 변화

  • Kang, Byung-Jun (Department of Materials Science and Engineering, Korea University) ;
  • Park, Sung-Eun (Department of Materials Science and Engineering, Korea University) ;
  • Lee, Seung-Hun (Department of Materials Science and Engineering, Korea University) ;
  • Kim, Hyun-Ho (Department of Materials Science and Engineering, Korea University) ;
  • Shin, Bong-Gul (Department of Materials Science and Engineering, Seoul National University of Technology) ;
  • Kwon, Soon-Woo (R&D Center, TS Corporation) ;
  • Byeon, Jai-Won (Department of Materials Science and Engineering, Seoul National University of Technology) ;
  • Yoon, Se-Wang (R&D Center, TS Corporation) ;
  • Kim, Dong-Hwan (Department of Materials Science and Engineering, Korea University)
  • 강병준 (고려대학교 신소재공학과) ;
  • 박성은 (고려대학교 신소재공학과) ;
  • 이승훈 (고려대학교 신소재공학과) ;
  • 김현호 (고려대학교 신소재공학과) ;
  • 신봉걸 (서울산업대학교 신소재공학과) ;
  • 권순우 (대한제당주식회사 중앙연구소) ;
  • 변재원 (서울산업대학교 신소재공학과) ;
  • 윤세왕 (대한제당주식회사 중앙연구소) ;
  • 김동환 (고려대학교 신소재공학과)
  • Received : 2010.10.14
  • Accepted : 2010.11.04
  • Published : 2010.11.27

Abstract

We have studied methods to save Si source during the fabrication process of crystalline Si solar cells. One way is to use a thin silicon wafer substrate. As the thickness of the wafers is reduced, mechanical fractures of the substrate increase with the mechanical handling of the thin wafers. It is expected that the mechanical fractures lead to a dropping of yield in the solar cell process. In this study, the mechanical properties of 220-micrometer-solar grade Cz p-type monocrystalline Si wafers were investigated by varying saw-damage etching conditions in order to improve the flexural strength of ultra-thin monocrystalline Si solar cells. Potassium hydroxide (KOH) solution and tetramethyl ammonium hydroxide (TMAH) solution were used as etching solutions. Etching processes were operated with a varying of the ratio of KOH and TMAH solutions in different temperature conditions. After saw-damage etching, wafers were cleaned with a modified RCA cleaning method for ten minutes. Each sample was divided into 42 pieces using an automatic dicing saw machine. The surface morphologies were investigated by scanning electron microscopy and 3D optical microscopy. The thickness distribution was measured by micrometer. The strength distribution was measured with a 4-point-bending tester. As a result, TMAH solution at $90^{\circ}C$ showed the best performance for flexural strength.

Acknowledgement

Supported by : 한국에너지 기술평가원(KETEP)

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