Journal of the Microelectronics and Packaging Society (마이크로전자및패키징학회지)

The Korean Microelectronics and Packaging Society (한국마이크로전자및패키징학회)
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High Speed Direct Bonding of Silicon Wafer Using Atmospheric Pressure Plasma

상압 플라즈마를 이용한 고속 실리콘 웨이퍼 직접접합 공정

  • Cha, Yong-Won ;
  • Park, Sang-Su ;
  • Shin, Ho-Jun ;
  • Kim, Yong Taek (Graduate School of NID Fusion Technology, Seoul National University of Science and Technology) ;
  • Lee, Jung Hoon (Graduate School of NID Fusion Technology, Seoul National University of Science and Technology) ;
  • Suh, Il Woong (Graduate School of NID Fusion Technology, Seoul National University of Science and Technology) ;
  • Choa, Sung-Hoon (Graduate School of NID Fusion Technology, Seoul National University of Science and Technology)
  • 차용원 (주식회사 엘트린) ;
  • 박상수 (주식회사 엘트린) ;
  • 신호준 (주식회사 엘트린) ;
  • 김용택 (서울과학기술대학교 NID 융합기술대학원) ;
  • 이정훈 (서울과학기술대학교 NID 융합기술대학원) ;
  • 서일웅 (서울과학기술대학교 NID 융합기술대학원) ;
  • 좌성훈 (서울과학기술대학교 NID 융합기술대학원)
  • Received : 2015.08.28
  • Accepted : 2015.09.09
  • Published : 2015.09.30
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Abstract

In order to achieve a high speed and high quality silicon wafer bonding, the room-temperature direct bonding using atmospheric pressure plasma and sprayed water vapor was developed. Effects of different plasma fabrication parameters, such as flow rate of $N_2$ gas, flow rate of CDA (clear dry air), gap between the plasma head and wafer surface, and plasma applied voltage, on plasma activation were investigated using the measurements of the contact angle. Influences of the annealing temperature and the annealing time on bonding strength were also investigated. The bonding strength of the bonded wafers was measured using a crack opening method. The optimized condition for the highest bonding strength was an annealing temperature of $400^{\circ}C$ and an annealing time of 2 hours. For the plasma activation conditions, the highest bonding strength was achieved at the plasma scan speed of 30 mm/sec and the number of plasma treatment of 4 times. After optimization of the plasma activation conditions and annealing conditions, the direct bonding of the silicon wafers was performed. The infrared transmission image and the cross sectional image of bonded interface indicated that there is no void and defects on the bonded wafers. The bonded wafer exhibited a bonding strength of average $2.3J/m^2$.

본 연구에서는 실리콘 웨이퍼의 고속 직접접합 공정을 위하여 상압 플라즈마와 함께 에어로젤 형태의 초순수 분사를 이용하여 표면처리 활성화 및 결함이 없는 실리콘 직접접합 공정을 개발하였다. 플라즈마 공정의 다양한 인자, 즉 $N_2$ 가스의 유량, CDA(clean dry air)의 유량, 플라즈마 헤드와 기판 간의 간격, 플라즈마의 인가전압이 플라즈마 활성화, 즉 친수화 처리에 미치는 영향을 접촉각 측정을 통하여 관찰하였다. 또한 열처리 온도 및 열처리 시간이 접합 강도에 미치는 영향을 연구하였으며, 접합 강도의 측정은 crack opening 방법을 이용하였다. 접합 강도가 제일 높은 최적의 열처리 조건은 $400^{\circ}C$의 열처리 온도 및 2 시간의 열처리 시간이었다. 플라즈마 스캔 속도 및 스캔 횟수를 실험계획법을 이용하여 최적화한 결과, 스캔 속도는 30 mm/sec, 스캔 횟수는 4 회에서 최적의 접합 강도를 나타내고 있었다. 열처리 조건과 플라즈마 활성화 조건을 최적화 한 후 직접접합을 하여 적외선투과현미경 등을 이용하여 관찰한 결과, 접합된 웨이퍼에서 접합 공정으로 인한 공극이나 결함은 관찰되지 않았다. 접합된 웨이퍼의 접합 강도는 평균 $2.3J/m^2$의 접합 강도를 나타내고 있었다.

Keywords

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