Tight-Pitch Au-Sn Interconnections for 3D-ICs Integration and Packaging Applications

Si TEG chips containing Au-Sn micro-bumps (μ- bump) with various sizes (varying from 3 to 20 μm) and pitch values (between 6 μm and 30 μm) were fabricated, and the flip-chip bonded chips were characterized for micro-structure and electrical resistance of Au-Sn μ-joints. An overall μ-joint height of -1.8 μm was obtained after thermal compression bonding at 180 'C for the 10 μm pitch μ-bumps with solder (Sn) height of 1.0-1.5 μm. The elemental analysis results showed that Au has diffused into the solder layer, and not vice-versa. The formation of seemless microstructure and the obtained resistance data reveal that the Au-Sn μ-joints with minimal height have tremendous potential for its application in the tight-pitch three- dimensional chip integration and packaging.