Roman Roth

Reliability aspects of copper metallization and interconnect technology for power devices

Abstract The introduction of thick copper metallization and topside interconnects as well as a superior die attach technology is improving the performance and reliability of IGBT power transistor technologies significantly. The much higher specific heat capacity and higher thermal conductivity increases the short circuit capability of IGBTs, which is especially important for inverters for drives applications. This opens the potential to further optimize the electrical performance of IGBTs for higher energy efficiency. The change in metallization requires the introduction of a reliable barrier against copper diffusion and copper silicide formation. This requires the development of an efficient test method and reliability assessment according to a robustness validation approach. In addition, the new metallization enables interconnects with copper bond wires, which yield, together with an improved die attach technology, a major improvement in the power cycling capability.

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 Infineons 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.