Journal of the Microelectronics and Packaging Society (마이크로전자및패키징학회지)

The Korean Microelectronics and Packaging Society (한국마이크로전자및패키징학회)
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Structural Characteristics of Ar-N2 Plasma Treatment on Cu Surface

Ar-N2 플라즈마가 Cu 표면에 미치는 구조적 특성 분석

  • Park, Hae-Sung (Department of Mechanical Engineering, Seoul National University of Science and Technology) ;
  • Kim, Sarah Eunkyung (Graduate School of Nano-IT Design Convergence, Seoul National University of Science and Technology)
  • 박해성 (서울과학기술대학교 일반대학원 기계공학과) ;
  • 김사라은경 (서울과학기술대학교 나노IT디자인융합대학원)
  • Received : 2018.11.14
  • Accepted : 2018.12.01
  • Published : 2018.12.31
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Abstract

The effect of $Ar-N_2$ plasma treatment on Cu surface as one of solutions to realize reliable Cu-Cu wafer bonding was investigated. Structural characteristic of $Ar-N_2$ plasma treated Cu surface were analyzed using X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscope. Ar gas was used for a plasma ignition and to activate Cu surface by ion bombardment, and $N_2$ gas was used to protect the Cu surface from contamination such as -O or -OH by forming a passivation layer. The Cu specimen under high Ar partial pressure plasma treatment showed more copper oxide due to the activation on Cu surface, while Cu surface after high $N_2$ gas partial pressure plasma treatment showed less copper oxide due to the formation of Cu-N or Cu-O-N passivation layer. It was confirmed that nitrogen plasma can prohibit Cu-O formation on Cu surface, but nitrogen partial pressure in the $Ar-N_2$ plasma should be optimized for the formation of nitrogen passivation layer on the entire surface of Cu wafer.

Cu-Cu 웨이퍼 본딩 강도를 향상시키기 위한 Cu 박막의 표면처리 기술로 $Ar-N_2$ 플라즈마 처리 공정에 대해 연구하였다. $Ar-N_2$ 플라즈마 처리가 Cu 표면의 구조적 특성에 미치는 영향을 X선 회절분석법, X선 광전자 분광법, 원자간력현미경을 이용하여 분석하였다. Ar 가스는 플라즈마 점화 및 이온 충격에 의한 Cu 표면의 활성화에 사용되고, $N_2$ 가스는 패시베이션(passivation) 층을 형성하여 -O 또는 -OH와 같은 오염으로부터 Cu 표면을 보호하기 위한 목적으로 사용되었다. Ar 분압이 높은 플라즈마로 처리한 시험편은 표면이 활성화되어 공정 이후 더 많은 산화가 진행되었고, $N_2$ 분압이 높은 플라즈마 시험편에서는 Cu-N 및 Cu-O-N과 같은 패시베이션 층과 함께 상대적으로 낮은 수치의 산화도가 관찰되었다. 본 연구에서는 $Ar-N_2$ 플라즈마 처리가 Cu 표면에서 Cu-O 형성 억제 반응에 기여하는 것을 확인할 수 있었으나 추가 연구를 통하여 질소 패시베이션 층이 Cu 웨이퍼 전면에 형성되기 위한 플라즈마 가스 분압 최적화를 진행하고자 한다.

Keywords

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Fig. 1. XRD spectra of all specimens (omega scan).

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Fig. 2. GIXRD spectra of all specimens (raw scale).

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Fig. 3. GIXRD spectra of all specimens (log scale).

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Fig. 4. XRD peak intensity analysis of copper nitride and copper oxide on Cu surface.

MOKRBW_2018_v25n4_75_f0005.png 이미지

Fig. 6. XPS profiles (a) Cu2p, (b) O1s, (c) N1s.

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Fig. 5. XPS profile of Cu2p peak etching before vs after (a) raw scale (b) nomalized intensity.

MOKRBW_2018_v25n4_75_f0007.png 이미지

Fig. 7. Peak deconvolution of the Cu2p, O1s and N1s.

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Fig. 8. 3D images of Surface by AFM.

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Fig. 9. Surface roughness analysis by AFM.

Table 1. Ar-N2 plasma treatment conditions.

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