The effect of coating the surface of a Cu microbump with a 1-hexanethiol self-assembled monolayer (SAM) on room-temperature solid-phase bonding was investigated. The microbump was cone-shaped while the counterelectrode was planar. Room-temperature bonding was performed by applying ultrasonic vibration. Chemical analysis showed that the SAM coating suppressed the surface oxidation of Cu. However, it was shown that the SAM coating also reduced the mechanical strength of the bonded interface, whereas little effect was observed in the electrical resistance of bump interconnects.
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