Elimination of Leakage in NaOH-Activated Cu/SiO₂ Hybrid Bonding for Plasma-Free Surface Activation Scheme

In this study, the effect of NaOH wet treatment on the leakage current in Cu/SiO2 hybrid structures is investigated. Samples with a comb-comb structure were treated with NaOH solution, followed by various post-cleaning steps. The leakage current (LC) behavior was observed after rinsing with deionized water (DIW) for 30 s, which was attributed to the residual of Na<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ions. However, extending the cleaning duration either using rinsing or sonication to 5 min effectively eliminated the LC behavior. These results emphasized the importance of post-cleaning for reliable, low-cost hybrid bonding without plasma treatments.