Investigations of copper wire bonding capability on plasma based additive copper metallizations

This paper describes and discusses a novel manufacturing process that enables an advanced top-level interconnection for power electronic applications. The commonly used aluminum bond wire process, where a friction welded connection is performed by the usage of ultrasonic on the substrate as well as on the semiconductor, is replaced by copper as a wire material. Thus, the overall performance of power electronic modules can be increased significantly because of the preeminent material characteristics of copper [1]. However, the higher hardness and lower ductility of copper in comparison to aluminum presuppose a functional coating on the silicon layers that absorbs the high bonding forces and protects the crystal structures from shattering. Different approaches for a selective copper metallization like galvanic metallization have been investigated and provide usable coating quality. Disadvantageously the processes are neither very flexible nor cost-effective and have also a bad environmental impact. The technology described in the following uses a current stabilized argon plasma to melt single copper particles which are then accelerated towards the substrate. Upon impact, the coating material solidifies and creates a diffusion-based adhesive layer on which the copper bonding process can be performed