AN EXPERIMENTAL AND NUMERICAL STUDY ON THE FORWARD-BIASED SOA OF IGBTS

Thermal and electrical destructions of n-ch 600 V punchthrough type IG BT's in F,B,SOA are investigated by experiments and simulations, The c ause of the thermal destruction is the thermal disappearance of built- in potential of p-n junction between the n(+) emitter and the p base o f the IGBT integral DMOSFET occurring at the critical temperature of s imilar to 650 K, Experiment and simulation results for the critical te mperature show a good agreement. The cause of the electrical destructi on is impact ionization at the n(-) drift/n(+) buffer junction in addi tion to the n(-) drift/p base junctions, That triggers a positive feed back mechanism of increasing IGBT integral pnp transistor current whic h causes the device to lose gate controllability. The experimentally o btained critical power dissipation is similar to 2000 kW/cm(2) This va lue is ten times greater than BJT's one. It was also found that emitte r ballast resistance (EBR) plays an important role in describing the F .B.SOA of IGBT's.