Antioxidative Cu Electrodeposition for 3D Interconnects with Hybrid Bonding

We found that the thickness of Cu oxide film varies with the type of acid Cu plating. Generally, the oxidation reaction of Cu first produces a monovalent Cu ion Cu⁺, which undergoes CuOH to form a cuprous oxide Cu2o film on the Cu surface. When Cu2o is exposed to an oxidizing environment, cupric oxide CuO is grown. The thickness of Cu oxide film formed after annealing at 150°C for 1 hour was measured by the sequential electrochemical reduction analysis (SERA) method, which is capable of distinguishing CuO and Cu2o. Consequently, the Cu oxide film grown after annealing mainly consisted of Cu2o, and we have confirmed that the thickness of Cu2o was highly related to additive factors such as concentration and molecular weight.