Low temperature (<180 °C) bonding for 3D integration

Three types of bonding, including Cu-In, Sn/In-Cu, and Cu/Ti-Ti/Cu, are investigated for the application of 3D interconnects. Cu-In bonding and Sn/In-Cu bonding can form intermetallic compounds at the bonding temperature lower than 180 °C. In addition, for Cu/Ti-Ti/Cu bonding, Cu can be protected from oxidation by capping Ti on Cu surface before bonding. This method can further decrease bonding temperature. All bonded structures have shown excellent electrical performance and reliability characteristics. Based on bond results, these structures can be applied for low temperature bonding in 3D interconnects.