Annealing Effects in Sub-8 μm Pitch Die-to-Wafer Hybrid Bonding

Hybrid bonding by dielectric-to-dielectric and copper-to-copper with the fine pitch is becoming the choice technology for heterogeneous integration, which provides higher I/O bandwidth with a smaller form factor. A die-to-wafer (D2W) hybrid bonding using Cu/dielectric interfaces plays an essential role in supporting miniaturization and further opens the significant possibility of stacking heterogeneous dies. In this work, a D2W hybrid bonding by SiO2 - SiO2 and Cu - Cu has been developed by the pick-and-place technique on a 200 mm platform. Several test structures have been designed with 4 × 4 μm2 bonding pads and 8 μm pitch. The fabricated 8 × 6 mm2 die2 on 20 × 20 mm2 die1 contains daisy chains ranging from 10 to 100,000 bonding links. Post-bonding effects of annealing temperatures from 200 - 350°C are investigated on bonding interfaces and electrical characteristics. Sub-micron alignment accuracy to 100% yield has been achieved. Functional 100k daisy chains of sub-8 μm pitch exhibit an astonishingly low 0.02 Ω/via resistance. Several pre- and post-physicals, as well as electrical characterizations, show an impressive 86-100% yield, marking a significant milestone.