Power Cu metallization for future power devices — Process integration concept and reliability

A novel power Cu front side chip metallization for insulated-gate bipolar transistors (IGBTs) and freewheeling diodes (FWDs) enabling thick Cu wire wedge bonding on active area is reported. In the continuing race to higher power density, main limitations of IGBT power modules are given by short circuit robustness requirements of the IGBT and power cycling capability of the front side Al wedge bond interconnect. Both topics are addressed by Infineon's 5th Generation of IGBT with XT joining technology [1, 2] enabling power density steps far beyond 30%. The developed Cu metallization with a special barrier layer structure allows Cu wedge bonding with high yield and extremely high reliability. The paper is describing firstly the device fabrication and secondly a novel reliability testing method (based on wafer level) covering the possible impact of the wire bond process.