Non thermal destruction mechanisms of IGBTs in short circuit operation

A number of experiments show that IGBTs have some non thermal destruction modes, which are similar to secondary breakdown in bipolar transistors. These are destruction just after turn-on, during the turn-off process in short circuit operation and during the turn-off process in an L-load operation. In this paper, the author reproduces the waves of the first and second destructions in isothermal transient simulations. In both cases, increasing the power supply voltage gradually, in a short circuit measurement, the pnp transistors in the IGBT would start to turn on, driven by electrons generated by impact ionization. Although this turn-on process has a positive feedback ability to increase the current, this current flows through a stray inductance (L_s) and causes a voltage drop. So, an IGBT has an ability to sustain some current density at a certain V_CE originally. However, if there was a local area whose pnp transistor is easier to turn on than the other major part, its current would not cease to increase because the voltage drop due to L_s was mainly decided by the increasing ratio of the majority current. The local area would inevitably latch up in a very short time. An IGBT has no destruction mechanism which is characterized by a universal constant, such as 200 kW/cm² for npn bipolar transistors. Nevertheless, the destruction limit of IGBTs could be evaluated as the ultimate operating voltage in a quasi-stationary simulation.