Increasing emitter efficiency in 3.3-kV enhanced trench IGBTs for higher short-circuit capability

Abstract

Abstract-In this paper, a 3.3-kV Enhanced Trench IGBT has been designed with a high emitter efficiency, for improving its short-circuit robustness. The carrier distribution profile has been shaped in a way that it is possible to increase the electric field at the surface of the IGBT, and thereby, counteract the Kirk Effect onset. This design approach is beneficial for mitigating high-frequency oscillations, typically observed in IGBTs under short-circuit conditions. The effectiveness of the proposed design rule is validated by means of mixed-mode device simulations. Then, two IGBTs have been fabricated with different emitter efficiencies and tested under short circuit, validating that the high-frequency oscillations can be mitigated, with higher emitter efficiency IGBT designs.

Modeling of IGBT With High Bipolar Gain for Mitigating Gate Voltage Oscillations During Short Circuit

“…Effect of collector doping concentration charge-field interactions can be counteracted by increasing the electric field at the emitter of the IGBT, in this way, the electric field becomes strong and not influenced by the excess of carriers in this region. One option to achieve a stronger electric field is to increase the hole injection, for example, by increasing the bipolar current gain α pnp [15]. This can be done by selecting a higher doping concentration of the p + collector layer.…”

“…The aim is to increase the electric field at the IGBT's surface and counteract the weak electric field. A sensitivity study has been performed in [6], [11], [15] and later in [10], varying different parameters and investigating its influence on the short-circuit oscillation behavior. Those studies have proven that the IGBT oscillations are more likely to be observed when the device is operated at low DC-link voltages, high positive gate voltages and low case temperatures, because the electric field becomes weaker at the emitter.…”