Mitsubishi Electric developed a Dual In-line Package Intelligent Power Module (DIP-IPM ver.4) with ratings of 50A and 75A/600V by developing the 5th generation full gate CSTBT (Carrier Storage Trench Bipolar Transistor).
In an IGBT, the resistance of the n- drift layer has to be kept high in order to withstand the blocking voltage at off-state. As the hole injection from collector to n- drift layer at on-state, the resistance of the n- drift layer is reduced, and power loss is reduced. However, the resistance of the n- drift layer near emitter side is difficult to reduce because the hole density here becomes low due to the far away distance to the collector. Hence, it is difficult to achieve a very low on-state voltage. CSTBT reaches a much lower on-state voltage by the
virtue of optimization of the hole density in the whole n- drift layer. A special n barrier called as carrier stored layer is designed under the P base layer to hinder the holes injected from the collector from penetrating to the emitter. This makes the further reduction of the on-state voltage possible because hole density is increased in the n- drift layer even near the emitter side. Since CSTBTis developed to be with high current carrying capability, sometimes it is designed in a structure called plugged cell merged CSTBTso as to ensure a certain withstanding capability against short circuit failure.
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