6.5kV IGBTs with improved Long Term DC Stability (LTDS)

Catastrophic failure of high voltage power semiconductors due to cosmic rays was identified in the 1990s. [1–3] As the phenomenon was characterized, device data sheets were modified to include a Long-Term DC Voltage Stability value (LTDS) to provide users with a DC application voltage rating below which the field failure rate would be less than 100 FIT. As IGBT voltage ratings increased to 6500V, the LTDS rating often became the limiting factor in applying the IGBT and efforts have been on-going to improve resistance to cosmic ray effects. Improvement in one power semiconductor characteristic typically requires trade-offs and compromises in other characteristics. This paper describes 6.5kV IGBTs with improved LTDS without sacrifice of electrical characteristics or performance. Verification and analysis results for an accelerated neutron irradiation experiment are reported.