A novel approach for increasing the strength of an Au/Si eutectic bonded interface on an oxidized silicon surface

The use of tantalum as adhesion layer for Au/Si eutectic bonding was investigated and compared to the frequently used materials chromium or titanium in the case of oxidized silicon substrates. Suitable test structures have been fabricated, bonded and evaluated. The eutectically bonded chips were characterized in respect to the maximum bearable tensile and shear loading. Interfacial reactions were observed by SEM and optical microscopy. As a significant result when tantalum was used, the external load until fracture occurred could be increased up to a factor of 3 in comparison to usually applied chromium or titanium. Analyses after bonding gave no prove for diffusion between the metallic alloy and the adhesion layer and delamination could be minimized therefore.