Long Term Stability and Drift Phenomena of different Trench IGBT Structures under Repetitive Switching Tests

The long term stability and special drift phenomena of different trench IGBT structures under multiple switching tests are experimentally evaluated. It can be confirmed that a state of the art trench IGBT structure shows a very stable dynamic performance, but another device structure with so called "unprotected" trenches undergoes a significant change in the switching behaviour within millions of switching pulses under over current conditions. A physical model for this strange behaviour is proposed that reproduces the observed real dynamic behaviour in a switching simulation. From the performed multiple switching tests a rough estimation is deduced resulting in the prediction that the test device structure would show a significant drift after 15 y of operation, whereas the standard device structure stays stable over the whole life time of 15 y.