Investigation and Optimization of Ultrathin Buffer Layers Used in Cu/Sn Eutectic Bonding

Ya Sheng Tang, Hsiu Chi Chen, Yi Tung Kho, Yu Sheng Hsieh, Yao Jen Chang, Kuan-Neng Chen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Ultrathin buffer layers (UBLs) with varied thickness ranging from 10 to 100 nm and different materials were used in Cu/Sn eutectic bonding. A Cu/Sn film thinner than 2 μm could fully react and became stiff and rough Cu-Sn intermetallic compound layer, which leads to failure bonding. Four kinds of semiconductor compatible materials including Ti, Pd, Co, and Ni were inserted between Cu/Sn to delay interdiffusion prior to eutectic bonding. In addition to symmetric Cu/Sn bonding with UBL, asymmetric Cu/Sn-Cu bonding scheme with 50-nm Ni UBL was demonstrated. With good mechanical properties, bonding quality, and electrical characteristics, the application of submicrometer Cu/Sn wafer-level bonding by assistance of buffering layer gives a promising and flexible platform for future 3-D integration applications.

Original languageEnglish
Pages (from-to)1225-1230
Number of pages6
JournalIEEE Transactions on Components, Packaging and Manufacturing Technology
Issue number7
StatePublished - 1 Jul 2018


  • 3-D integration
  • eutectic bonding
  • ultrathin buffer layer (UBL)

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