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.
|Number of pages||6|
|Journal||IEEE Transactions on Components, Packaging and Manufacturing Technology|
|State||Published - 1 Jul 2018|
- 3-D integration
- eutectic bonding
- ultrathin buffer layer (UBL)