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Effect of NH4OH Treatment on Plasma‐Assisted InP/Al2O3/SOI Direct Wafer Bonding

The effect of NH4OH treatment on InP/Al2O3/SOI direct wafer bonding is investigated. The atomic force microscope (AFM) and water contact angle (CA) results reveal a decrease in root‐mean‐square (RMS) surface roughness and CA of the NH4OH‐treated InP wafer. X‐ray photoelectron spectroscopy (XPS) analysis is carried out to ascertain the chemical composition of the bonding surfaces. It is found that NH4OH treatment followed by plasma activation increases the content of oxides on the surface of InP wafer. Based on these results, it is concluded that NH4OH treatment helps increase hydrophilicity and contact area of the bonding surface, thus contributing to the success of plasma‐assisted InP/Al2O3/SOI wafer bonding.