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

Abstract

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.

Wafer-Level Vacuum Packaging of Smart Sensors

“…Au 0.82 Si 0.18 eutectic bonding, originally developed and adopted as a die attach process [53], has more recently been demonstrated for transfer printing of light emitting diodes (LEDs) [54] and as a wafer bonding method for absolute pressure sensors [55], a MEMS Pirani vacuum gauge with CMOS elements [56,57,58], and other MEMS and smart sensors using surrogate wafers [56,57,58,59,60,61,62,63,64,65,66]. In this approach, Au is deposited by evaporation, sputtering, or electroplating.…”

Interaction of gold nanoparticles with a TiO2film formed on Si(100)

“…7) Therefore, in order to form stable electrodes by the deposition of Au on Si substrates, a passivation layer of metals such as Ti, Cr, and Ta should be formed between Au NPs and the Si substrate. 9) On the other hand, in order to use fine structures of Au NP arrays as conducting wires, it is necessary to insulate Au NPs from the Si substrate. In this case, the insulating layer should also act as a passivation layer against the diffusion of Si atoms into Au NP arrays.…”