Time Evolution Study of Two-Step Plasma-Treated Copper-Copper Direct Bonding in Ambient

In this paper, a two-step plasma-treated copper-copper direct bonding performed in ambient condition, followed by pressure-less annealing, is reported. A decent shear strength of ~38 MPa is achieved. The hermeticity of the bonded copper dies degrades with prolonged exposure in the ambient. No undesirable materials are observed at the copper-copper bonding interface, which suggests the formation of high-quality bonding. This bonding technology would be applicable for high-throughput 3D heterogeneous integration and advanced packaging.