Authored By:
Yoshinori Ejiri, Masumi Sakamoto, Chiaki Shimizu
Resonac Co., Ltd.
Ibaraki, Japan
Summary
In this study, we developed a Cu paste that can be used as a filling material for through silicon via (TSV), through glass via (TGV), and organic substrates. Non-through holes with diameters ranging between 20 and 100 μm and depths ranging between 70 and 100 μm (aspect ratios from 1 to 3.5) formed in a silicon surface layer were filled with Cu paste. TGV substrates with diameters ranging between 30 and 90 μm and thickness of 300 μm were filled with Cu paste without cracking. Multilayer substrates with the diameters of 180 and 260 μm and a thickness of 6.4 mm (aspect ratios: 25, 36) were filled with Cu paste without cracking.
The 2.5D chip package was prepared using a TSV filled with Cu paste as a 2.5D interposer. The 2.5D chip package was verified through reliability test [thermal cycle test (TCT), high temperature storage test (HTST), un-bias high accelerated stress test (HAST) and pressure cooker test (PCT)]. After the reliability test, the conductive resistance of the package that adopted the Cu paste was found to be within 10％ of the initial value. Moreover, we found that Cu paste can be applied to 2.5D interposer as filling material.
Conclusions
We developed a Cu paste that can be used as a filling material for TSVs, TGVs, and organic substrates. The following key conclusions are obtained:
(1) The film with the lowest volume resistivity of approximately 3.5 μΩ･cm was obtained at 350 °C or higher in hydrogen atmosphere.
(2) Non-through holes with diameters of 20–100 μm and depths of 70–100 μm (aspect ratios from 1 to 3.5) formed in a silicon surface layer were filled with Cu paste.
(3) TGV substrates with a diameter of 30, 60, 90 μm and a thickness of 300 μm were filled with Cu paste without inducing cracks.
(4) It was found that Cu paste can be formed without inducing cracks even when using a thick and high-aspect-ratio organic substrate (thickness: 6.4 mm; aspect ratio: 25, 36).
(5) The 2.5D chip package was prepared using a TSV filled with Cu paste as a 2.5D interposer. After the reliability test, the conductive resistance of the package was found to be within 10％ of the initial value. We found out that the Cu paste can be applied to 2.5D interposer as filling material.
Initially Published in the SMTA Proceedings
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