Assessment of the Indium Chemical Mechanical Polishing Mechanism via Corrosion Analysis

The mechanism by which chemical mechanical polishing of In proceeds was investigated to assess the potential integration of this metal into quantum chiplets. Both acidic and alkaline slurries containing hydrogen peroxide (H 2 O 2 ) as the oxidant and silica nanoparticles as the abrasive were employed, and the electrochemical properties of polished In were analyzed. These properties included corrosion characteristics, passivation reactions, and ion kinetics under different conditions. The surface In layer remained stable in its metallic state in contact with either slurry in the absence of H 2 O 2 . Under these conditions, the In surface became more reactive, increasing removal rate, but the process was difficult to control, with a higher risk of pitting or surface roughness. In contrast, with H 2 O 2 present, the In underwent a distinct phase transformation. Specifically, In 3+ ions were generated in the acidic slurry while In 2 O 3 was formed in the alkaline slurry. The addition of H 2 O 2 promoted formation of stable oxides, enabling improved surface control and supporting gentle polishing or selective material removal. The In removal rates and roughnesses were 215 and 210 nm min −1 , 28 and 27 nm, in the alkaline and acidic slurries, respectively. Increasing H 2 O 2 concentration also reduced the removal rate and roughness in both slurry systems.