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Modern IGBT structure with a highly doped buffer layer showed a MOSFET-like behavior at low collectoremitter voltage when the gate was fully turned-on. This significantly increased the conduction loss and resulted in scrap chips. Its failure mechanism has been systematically studied in this paper to reveal the underlying device physics inside the IGBT microstructure using energy-band theory, numerical simulation and equivalent circuit methods. It is reported that both tunneling current and low injection efficiency of highly doped p-emitter/n-buffer junction are root causes, and the latter deactivates the bipolar function, so that the device is dominated by MOSFET action only under low collector-emitter voltage condition. The paper will be concluded by presenting excellent measured performances of IGBTs using optimized p-emitter/nbuffer junction.

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Developing suitable processes for thin wafer fast recovery power diodes is important for modern production plants as the substrate dimension increases. A set of emerging technologies has been employed here in order to fabricate 1700V rated fast recovery diodes from standard Si IGBT substrates without pre-diffused backside n-type buffer. Wafer grinding, n + back surface contact implant, laser annealing and multiple proton implantations were all employed here for the diode fabrication. Detailed processing parameters for each step were carefully selected and optimized for the fabrication. Both SRIM and Silvaco simulations were carried out to initially provide theoretical guide for experimental design and later compared with measured results. The fabricated diodes were tested under both static and dynamic recovery conditions. The results demonstrate that the processing technologies used here are capable of making fast recovery diodes from standard IGBT substrates.

In this work, the methodology and procedures of lifetime prediction for power IGBT modules are presented. Firstly, we discuss the long term reliability tests of power modules for developing lifetime models, and review some reported lifetime models. Then, the procedures of lifetime prediction in real applications are addressed, which include power loss calculations based on the actual mission profile, the conversion of power loss profile to temperature profile according to the module's thermal properties, the temperature cycles counting by Rainflow algorithm, and lifetime calculation by the fatigue linear accumulation damage theory. Finally, the lifetime of a 3300V/800A IGBT module manufactured by Dynex Semiconductor of China Southern Railway applied in metro traction systems is predicted.