[논문]첨단 반도체 패키징을 위한 미세 피치 Cu Pillar Bump 연구 동향

노은채; 이효원; 윤정원

doi:10.6117/kmeps.2023.30.3.001

첨단 반도체 패키징을 위한 미세 피치 Cu Pillar Bump 연구 동향
Recent Advances in Fine Pitch Cu Pillar Bumps for Advanced Semiconductor Packaging 원문보기

마이크로전자 및 패키징 학회지 = Journal of the Microelectronics and Packaging Society, v.30 no.3, 2023년, pp.1 - 10

노은채 (충북대학교 신소재공학과) , 이효원 (충북대학교 신소재공학과) , 윤정원 (충북대학교 신소재공학과)

초록
AI-Helper

최근, 고사양 컴퓨터, 모바일 제품의 수요가 증가하면서 반도체 패키지의 고집적화, 고밀도화가 요구된다. 따라서 많은 양의 데이터를 한 번에 전송하기 위해 범프 크기 및 피치 (Pitch)를 줄이고 I/O 밀도를 증가시킬 수 있는 플립 칩 (flip-chip), 구리 필러 (Cu pillar)와 같은 마이크로 범프 (Micro-bump)가 사용된다. 하지만 범프의 직경이 70 ㎛ 이하일 경우 솔더 (Solder) 내 금속간화합물 (Intermetallic compound, IMC)이 차지하는 부피 분율의 급격한 증가로 인해 취성이 증가하고, 전기적 특성이 감소하여 접합부 신뢰성을 악화시킨다. 따라서 이러한 점을 개선하기 위해 UBM (Under Bump Metallization) 또는 Cu pillar와 솔더 캡 사이에 diffusion barrier 역할을 하는 층을 삽입시키기도 한다. 본 review 논문에서는 추가적인 층 삽입을 통해 마이크로 범프의 과도한 IMC의 성장을 억제하여 접합부 특성을 향상시키기 위한 다양한 연구를 비교 분석하였다.

Abstract ▼ AI-Helper

Recently, as the demand for high-performance computers and mobile products increases, semiconductor packages are becoming high-integration and high-density. Therefore, in order to transmit a large amount of data at once, micro bumps such as flip-chip and Cu pillar that can reduce bump size and pitch and increase I/O density are used. However, when the size of the bumps is smaller than 70 ㎛, the brittleness increases and electrical properties decrease due to the rapid increase of the IMC volume fraction in the solder joint, which deteriorates the reliability of the solder joint. Therefore, in order to improve these issues, a layer that serves to prevent diffusion is inserted between the UBM (Under Bump Metallization) or pillar and the solder cap. In this review paper, various studies to improve bonding properties by suppressing excessive IMC growth of micro-bumps through additional layer insertion were compared and analyzed.

주제어

표/그림 (17)

그림 Fig. 1. 3D Package structure (a) CS, (b) CNS and (c) CNCS.⁴²⁾
그림 Fig. 2. SEM micrographs of Cu pillars (a) without solder caps and (b) with lead-free solder cap after reflow.⁴⁴⁾
$Fig. 3. Schematic illustration showing the fracture mechanisms during aging at 180℃ from 0 to 750 h.46)$ 그림 Fig. 3. Schematic illustration showing the fracture mechanisms during aging at 180℃ from 0 to 750 h.⁴⁶⁾
$Fig. 4. SEM images of the fractured surfaces; (a-c) as-bonded, (d-f) after 50 h of annealing, (g-i) after 500 h of annealing.47)$ 그림 Fig. 4. SEM images of the fractured surfaces; (a-c) as-bonded, (d-f) after 50 h of annealing, (g-i) after 500 h of annealing.⁴⁷⁾
그림 Fig. 5. Cross-sectional SEM-BSE images of Cu pillar bumps annealed at 150℃ for (a) 0 h and (b) 360 h.⁴⁸⁾
그림 Fig. 6. Diagram and SEM image of joints in cross-section after TCB with Ni barrier structures.⁴⁹⁾
그림 Fig. 8. Shear strength and gap of the bonding sample: (a), (d) force varied and (b), (e) time varied (c), (f) temperature varied.⁴⁹⁾
그림 Fig. 7. SEM analysis results of the bonding sample: (a) morphology of Cu/Ni/Sn layers, and (b) composition profile obtained from the points marked by squares in (a). ⁴⁹⁾
$Fig. 9. Schematics of fracture sites in the Cu/Ni samples.50)$ 그림 Fig. 9. Schematics of fracture sites in the Cu/Ni samples.⁵⁰⁾
그림 Fig. 10. Sequential SEM images of Cu/Ni/Sn-2.5Ag microbumps with small solder volume during EM test at 150℃ with a current density of 1.5 × 10⁵ A/cm² with downward e lectron flow (a) 0 h (b) 180 h (c) 600 h.⁵¹⁾
그림 Fig. 11. Cross-section images of Sn bump without voids during multiple reflow.⁵²⁾
그림 Fig. 12. SEM images of the micro-bumps annealed at 170°C for (a) four days and (b) 285 h.⁵³⁾
그림 Fig. 13. The results of multiple reflow test.⁴²⁾
그림 Fig. 14. Cross-sectional SEM micrographs of the Cu/Ni/solder/Ni/Cu bonding structure after thermal aging at 443 K (170°C) for various lengths of time.⁵⁴⁾
그림 Fig. 15. Cross-sectional SEM micrographs of the Cu/Ni/Cu/solder/Cu/Ni/Cu bonding structure after thermal aging at 443 K for various lengths of time.⁵⁴⁾
그림 Fig. 16. Schematic diagrams illustrating the formation mechanism of rod-like Cu₆Sn₅ IMC for the conventional solder joints (a-d) and the case of the Sn/Cu/Ni(P)/Cu joints (e-h).⁵⁵⁾
그림 Fig. 17. Bonding strength of the samples with a Ni(P)/Cu bi-layer barrier (circle) and a Ni(P) barrier (square).⁵⁵⁾

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표제어: PCR

동의어: Packet Collision Rate

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용어 설명: PCR은 세균 특이성이 있는 primer를 이용하여 적은 수의 세균이 있을지라도 쉽게 검출할 수 있는 유용한 방법이며, 이를 이용하여 구강 내 치면세균막이나 타액에서 직접 세균을 검출할 수 있게 되었다[8].

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