Electrothermal simulations in punchthrough and nonpunchthrough IGBT's

The performance of 1200 V punchthrough (PT) and nonpunchthrough (NPT) insulated gate bipolar transistors (IGBT's) is studied in detail under unclamped inductive switching (UIS) and short circuit (SC) conditions. The need for a good physics based simulator to carry out a reliability study is pointed out in the paper. Using such a finite element-based device and circuit simulator it is shown that NPT-IGBT's show a much better performance than PT-IGBTs under UIS condition. It is also shown that an NPT device has a better short circuit withstanding capability than a PT device due to the structural differences between the two devices. As there is a huge power loss within the device during these operating conditions, device self-heating is expected to have a significant impact on device characteristics. Electrothermal simulations are used to study device self-heating and it is shown that it significantly influences device performance under SC operation whereas self-heating influences the UIS performance of only the PT device with little effect on the NPT device. The study is validated by an experimental study of short circuit failure of PT IGBTs.