Ar/N2 plasma surface activation in ambient environment for Cu-Cu bonding has been performed and characterized. Cu-Cu bonding occurs at room temperature and under normal atmospheric conditions. Post-bonding annealing is performed at 300 °C and below to control the overall thermal budget. Shear strength and hermeticity property of samples with varying annealing temperature are investigated. Samples annealed at 250 °C demonstrates the highest average shear strength of 20.3 MPa and lowest average helium leak rate of 8.7 × 10-9 atm.cc/s. Daisy chain structures are used to examine the electrical property of sample bonded at 300 °C and temperature cycling tests from -40 to 125 ºC for 1,000 cycles have been performed for reliability assessment. It is observed that the dies are well bonded and intact after 1,000 cycles even though the exposed Cu surface is heavily oxidized.

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