Effect of HF & H2SO4 pretreatment on interfacial adhesion energy of Cu–Cu direct bonds

Effects of HF & H2SO4 pretreatment conditions on the interfacial bonding strength of Cu–Cu direct bonds were systematically investigated. The evaluated interfacial adhesion energies for 3 μm-thick Cu bonding layers were 0.58, 0.46, and 4.90 J/m2 for different HF & H2SO4 pretreatment times of 0, 15, and 30 s, respectively, with bonding temperature of 350 °C, which is ascribed to the effective removal of native surface oxide at optimum wet cleaning conditions before Cu–Cu bonding.

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► Effects of HF & H2SO4 pretreatment on the bonding toughness of Cu–Cu bonds were investigated.
► The interfacial adhesion energies for Cu bonding layers were 0.58 to 4.90 J/m2 each condition.
► This result shows that the effective removal of native surface oxide at optimum wet cleaning conditions before Cu-Cu bonds.