마이크로전자및패키징학회지 (Journal of the Microelectronics and Packaging Society)

  • 제25권4호
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  • Pages.83-88
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  • 2018
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  • 1226-9360(pISSN)
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  • 2287-7525(eISSN)
한국마이크로전자및패키징학회 (The Korean Microelectronics and Packaging Society)
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NCF Trap이 Cu/Ni/Sn-Ag 미세범프의 Electromigration 특성에 미치는 영향 분석

Effect of NCF Trap on Electromigration Characteristics of Cu/Ni/Sn-Ag Microbumps

  • 류효동 (안동대학교 신소재공학부 청정에너지소재기술연구센터) ;
  • 이병록 ((주)스태츠칩팩코리아) ;
  • 김준범 ((주)하나마이크론) ;
  • 박영배 (안동대학교 신소재공학부 청정에너지소재기술연구센터)
  • 투고 : 2018.11.25
  • 심사 : 2018.12.21
  • 발행 : 2018.12.31
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초록

Cu/Ni/Sn-Ag 미세범프 접합 공정후 Ni/Sn-Ag접합계면에 잔류한 비전도성 필름(non-conductive film, NCF) trap 형성이 전기적 신뢰성에 미치는 영향을 분석하기 위해 온도 $150^{\circ}C$, 전류밀도 $1.5{\times}10^5A/cm^2$ 조건에서 electromigration (EM) 신뢰성 실험을 진행하였다. EM 신뢰성 실험 결과, NCF trap이 거의 없는 Cu/Ni/Sn-Ag 미세범프가 NCF trap이 형성된 미세범프 보다 약 8배 긴 EM 수명을 보여주고 있다. 저항 변화 및 손상계면에 대한 미세구조 분석결과, Ni/Sn-Ag접합계면에 공정 이슈에 의해 형성된 NCF trap이 Ni-Sn 금속간화합물/Sn-Ag솔더계면에 보이드를 유발하여 EM 원자 확산을 방해하기 때문에 빠른 보이드 성장에 의한 전기적 손상이 일찍 발생하는 것으로 판단된다.

The electromigration (EM) tests were performed at $150^{\circ}C$ with $1.5{\times}10^5A/cm^2$ conditions in order to investigate the effect of non-conductive film (NCF) trap on the electrical reliability of Cu/Ni/Sn-Ag microbumps. The EM failure time of Cu/Ni/Sn-Ag microbump with NCF trap was around 8 times shorter than Cu/Ni/Sn-Ag microbump without NCF trap. From systematic analysis on the electrical resistance and failed interfaces, the trapped NCF-induced voids at the Sn-Ag/Ni-Sn intermetallic compound interface lead to faster EM void growth and earlier open failure.

키워드

MOKRBW_2018_v25n4_83_f0001.png 이미지

Fig. 1. Schematic diagrams of (a) Cu/Ni/Sn-Ag microbumps with and without NCF trap, (b) daisy chain structure for EM test.

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Fig. 2. As-bonded cross-sectional SEM images of Cu/Ni/Sn-Ag microbumps (a) with NCF trap and (b) without NCF trap.

MOKRBW_2018_v25n4_83_f0003.png 이미지

Fig. 3. As-bonded SEM image of bottom Cu/Ni surface after solder etching of Cu/Ni/Sn-Ag microbumps with NCF trap.

MOKRBW_2018_v25n4_83_f0004.png 이미지

Fig. 4. Resistance change versus time curve of Cu/Ni/Sn-Ag microbumps for 1.5 × 105 A/cm2 at 150℃: (a)with and without NCF trap, and (b) enlarged graph of Cu/Ni/Sn-Ag microbumps with NCF trap.

MOKRBW_2018_v25n4_83_f0005.png 이미지

Fig. 5. Sequential SEM micrographs of Cu/Ni/Sn-Ag microbumps with NCF trap during current stressing at 150℃ , 1.5 × 105 A/cm2: (a) 10h, (b) 30h, (c) 60h.

MOKRBW_2018_v25n4_83_f0006.png 이미지

Fig. 6. Sequential SEM micrographs of Cu/Ni/Sn-Ag microbumps without NCF tarp during current stressing at 150℃ , 1.5 × 105 A/cm2: (a) 10h, (b) 300h, (c) 600h.

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