Low-Temperature Cu/Cu Hydrophilic Bonding Using Ar Ion Beam Activation

With Ar ion beam activation, 4-inch Cu wafers were bonded by hydrophilic bonding at 200°C. The effects of the bonding atmosphere and post-annealing temperature on the Cu/Cu bonding were investigated. For all bonded Cu/Cu pairs, extremely strong bonding with a bond strength of over 7 J/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> was achieved. When bonding was conducted in vacuum, an oxide-free interface was obtained. However, at the interface bonded in air, oxide nodules were observed. With an increase in post-annealing temperature from 200°C to 350 ºC, most of oxide nodules disappeared, and small voids caused by the disappearance of oxide nodules coalesced.