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CIBH Diode with Superior Soft Switching Behavior in 3.3 kV Modules for Fast Switching Applications

A new technology for the vertical architecture of free wheeling diodes (FWDs) is introduced, which is optimized for applications with high switching frequencies. To minimize the turn off losses of the diode and the turn on losses of the IGBT, for the first time a diode with the CIBH (Controlled Injection of Backside Holes) concept is implemented. The CIBH diode allows to reduce the charge stored in the diode by minimizing the wafer thickness and reducing the doping concentration of the backside emitter, whereas an excellent switching softness remains even under extreme switching conditions. The advantage of the CIBH technology for high power applications is shown by investigations in IHV modules with 1500A current rating and comparisons to state-of-the-art FWDs. The performance improvement of the CIBH diode is achieved by implanting buried p doped layers at the cathode side in front of the n+ cathode, which can be seen in Fig. 2. During reverse recovery the buried p-doped areas inject holes in the base region improving the ruggedness and softness of fast diodes. This effect is called Controlled Injection of Backside Holes.

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• 2008/06/06