Cu–Cu Bonding in Ambient Environment by Ar/N₂ Plasma Surface Activation and Its Characterization

摘要

Ar/N-2 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. Postbonding annealing is performed at 300 degrees 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 degrees C demonstrate the highest average shear strength of 20.3 MPa and the lowest average helium leak rate of 8.7x10(-9) atm.cc/s. Daisy chain structures are used to examine the electrical property of sample bonded at 300 degrees C, and the temperature cycling tests from -40 degrees C to 125 degrees C for 1000 cycles have been performed for the reliability assessment. It is observed that the dies are well-bonded and intact after 1000 cycles even though the exposed Cu surface is heavily oxidized.