Time-Dependent Evolution Study of Plasma-Treated Al Surface Enabling Two-Step Al-Al Direct Bonding in Ambient

In this paper, time-dependent evolution properties of Ar/N2 plasma-treated Al surface for two-step D2D Al-Al direct bonding in ambient is studied. Surface roughness is assessed on the Al surface both before and after plasma treatment, demonstrating that the plasma-treated Al surface remains as an "activated" status for up to ~6 hours compared to the as-deposited Al surface. The plasma-treated Al dies exposed in ambient for different durations are bonded in ambient environment, followed by batch annealing at 300°C. The bonded dies are examined for bonding microinterface quality, bonding strength, and hermeticity. The outcomes confirm successful bonding with the desired performances. This reported bonding technology would be a promising candidate for high-throughput heterogeneous integration and advanced packaging.