A Collective Die to Wafer Bonding Approach Based on Surface-Activated Aluminum–Aluminum Thermocompression Bonding

This work presents a collective die to wafer (D2W) bonding concept based on surface-activated aluminum–aluminum (Al–Al) thermocompression bonding, which involves the fabrication of a reusable silicon carrier wafer onto which the dies are placed without additional adhesives. Compared to other methods, the absence of adhesives allows the subsequent processing under ultrahigh vacuum, which is beneficial for low-temperature Al–Al bonding. The Al–Al bonding is performed in an EVG ComBond system, where an argon plasma is used to remove the native oxide. The thermocompression bonding is carried out for 1 h at a temperature of 300 °C with a pressure between 52 and 60 MPa. This article shows an Al–Al collective D2W bonding process with high yield >90%, excellent bond strength >90 MPa, and contact resistances in the milliohms range.