Torleif Tollefsen
SINTEF & Vestfold University College, Norway
October 25, 2011 | 12:00 to 01:00 | 540 Cory Hall, DOP Center Conference Room
Host: Debbie Senesky
Au-Sn solid-liquid-interdiffusion (SLID) bonding is a novel and promising interconnect technology for high temperature (HT) applications. In combination with Silicon Carbide (SiC) devices, Au-Sn SLID has the potential of being a key technology for the next generation of innovative, cost-effective and environmentally friendly drilling and well intervention systems for the oil industry. However, limited knowledge about Au-Sn SLID bonding for HT applications is a major restriction to fully realizing the high temperature potential of SiC devices. Two different processing techniques - electroplating of Au/Sn layers and sandwiching of eutectic Au-Sn preform between electroplated Au layers - have been studied in a simplified metallization system. The latter process was further investigated in two different Cu/Si3N4/Cu/NiP/Au-Sn/Ni/Ni2Si/SiC systems (different Au-layer thickness). Die shear tests and cross-sections have been performed on "as bonded," thermally cycled and thermally aged samples to characterize the bonding properties associated with the different processing techniques, metallization schemes and environmental stress tests. A uniform Au-rich bond interface is produced (with a melting point of 522°C). The importance of excess Au on both substrate and chip side in the final bond is demonstrated. It is shown that Au-Sn SLID can absorb thermo-mechanical stresses induced by large CTE mismatches (up to 12 ppm/K) in a package during HT thermal cycling. The bonding strength of Au-Sn SLID is shown to be superb, exceeding 78 MPa. Importantly, Au-Sn SLID is shown to be an excellent bonding technology for HT packaging.
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