Surface Modification by Wet Treatment for Low-Temperature Cu/SiO₂ Hybrid Bonding

Based on the surface analyses and bonding results, we concluded that the optimal wet surface modification solution are 0.5 M for both NaOH and KOH, which not only achieve sufficient hydrophilicity for bonding but also have the least roughening on the sample surface. Utilizing this treatment, we achieved robust Cu/SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> hybrid bonding with no noticeable gaps at the bonding interfaces at 200°C without pressure. A very low specific contact resistance of 3.4×10 −9 Ω/cm 2 can be obtained using the optimal wet treatment conditions.