Journal of the Microelectronics and Packaging Society (마이크로전자및패키징학회지)

The Korean Microelectronics and Packaging Society (한국마이크로전자및패키징학회)
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Study of Organic-inorganic Hybrid Dielectric for the use of Redistribution Layers in Fan-out Wafer Level Packaging

팬 아웃 웨이퍼 레벨 패키징 재배선 적용을 위한 유무기 하이브리드 유전체 연구

  • Song, Changmin (Graduate school of Nano-IT Design Convergence, Seoul National University of Science and Technology) ;
  • Kim, Sarah Eunkyung (Graduate school of Nano-IT Design Convergence, Seoul National University of Science and Technology)
  • 송창민 (서울과학기술대학교 나노IT디자인융합대학원) ;
  • 김사라은경 (서울과학기술대학교 나노IT디자인융합대학원)
  • Received : 2018.09.17
  • Accepted : 2018.11.30
  • Published : 2018.12.31
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Abstract

Since the scaling-down of IC devices has been reached to their physical limitations, several innovative packaging technologies such as 3D packaging, embedded packaging, and fan-out wafer level packaging (FOWLP) are actively studied. In this study the fabrication of organic-inorganic dielectric material was evaluated for the use of multi-structured redistribution layers (RDL) in FOWLP. Compared to current organic dielectrics such as PI or PBO an organic-inorganic hybrid dielectric called polysilsesquioxane (PSSQ) can improve mechanical, thermal, and electrical stabilities. polysilsesquioxane has also an excellent advantage of simultaneous curing and patterning through UV exposure. The polysilsesquioxane samples were fabricated by spin-coating on 6-inch Si wafer followed by pre-baking and UV exposure. With the 10 minutes of UV exposure polysilsesquioxane was fully cured and showed $2{\mu}m$ line-pattern formation. And the dielectric constant of cured polysilsesquioxane dielectrics was ranged from 2.0 to 2.4. It has been demonstrated that polysilsesquioxane dielectric can be patterned and cured by UV exposure alone without a high temperature curing process.

집적회로 소자의 축소가 물리적 한계에 도달 한 이후 3D 패키징, 임베디드 패키징 및 팬 아웃 웨이퍼 레벨 패키징(FOWLP, fan-out wafer level packaging)과 같은 혁신적인 패키징 기술들이 활발히 연구되고 있다. 본 연구에서는 FOWLP의 다층 재배선(redistribution layer)에 사용하기 위한 유무기 하이브리드 유전체 소재의 공정을 평가하였다. 폴리이미드(PI) 또는 폴리파라페닐렌벤조비스옥사졸(PBO)과 같은 현 유기 유전체와 비교하여 폴리실세스키옥산(polysilsesquioxane, PSSQ)라고 불리는 유무기 하이브리드 유전체는 기계적, 열적 및 전기적 안정성을 향상시킬 수 있고, UV 노광을 통하여 경화 공정과 패턴 공정을 동시에 할 수 있는 장점이 있다. 폴리실세스키옥산 용액을 6 인치 Si 웨이퍼에 스핀 코팅한 후 pre-baking과 UV 노광 공정을 이용하여 패턴 및 경화를 진행하였다. 10분의 UV 노광 시간으로 경화와 $2{\mu}m$ 라인 패턴 형성이 동시에 진행됨을 확인하였고, 경화된 폴리실세스키옥산 유전체의 유전상수는 2.0에서 2.4 로 측정되었다. 폴리실세스키옥산 소재를 이용하여 고온 경화 공정없이 UV 노광 공정만으로 경화와 패턴을 할 수 있는 공정 가능성을 보였다.

Keywords

MOKRBW_2018_v25n4_53_f0001.png 이미지

Fig. 1. PSSQ coating images: (a) PSSQ Type 1, (b) PSSQ Type 2, (c) PSSQ Type 3.

Table 1. Photo-definable PSSQ Composition.

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Fig. 2. Schematic of PSSQ process flow: (a) spin coating, (b) baking, (c) exposure, (d) developing.

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Fig. 3. PSSQ thin film thickness per rotational speed.

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Fig. 4. EDS analysis of agglomerated spots in PSSQ Type 3 surface.

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Fig. 5. FITR analysis: (a) PSSQ Type 1, (b) PSSQ Type 2, and (c)PSSQ Type 3.

MOKRBW_2018_v25n4_53_f0007.png 이미지

Fig. 6. Dielectric constant and tangent loss.

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Fig. 7. SEM cross-sectional images of PSSQ patterns.

Table 2. Exposure and Developing Conditions.

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