Copper metallization on silicon power devices for heavy copper wire-bonding

The use of heavy copper wire-bonds as topside contact in the assembly and interconnect technology of silicon-based power modules promises a more than tenfold increase of the thermal cycling reliability of the assembly over the currently used heavy aluminum wires. This increase is contrasted by the increased hardness of copper over aluminum. To date, the higher hardness of the thick copper wires requires a higher bonding force and ultrasonic power for an adequate bond formation which induces a strong deformation of the available power device topside metallizations and leads to a destruction of the devices. Based on the state-of-the-art Back-End-of-Line process chain, a new copper metallization scheme is developed. The plan is adapted for specific process steps to acknowledge the characteristic differences of the deposition and usage of copper on silicon devices. At the end, a copper metallization is presented which allows for the use of heavy copper wire-bonding on silicon power devices.