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A temperature of 200degC for the PN junction of power silicon devices (diodes, thyristors, transistors) is known as a limit for their reliable performance. PN junction failure after operation above this temperature consists in excessive high current or even electrical short circuit when reverse bias voltage is applied. Enough information in the published literature on this subject does not exist at this time. PN junction devices available at this time on the market were measured and placed in a hot chamber at constant ambient temperature higher than 200degC. Junction blocking voltage was applied and the level of leakage current was monitored. The silicon die after decapsulation of failed devices exhibits a small region of material degradation located at the junction periphery, causing excessive high leakage or short-circuit of the junction. The leakage current flowing at the interface between semiconductor and the passivating dielectric layer from the junction edge is a key factor involved in device failure. Lower level and uniform distribution of this current around the junction periphery can enable reliable operation above 200degC. Experimental results are presented and analyzed.
Date of Conference: 16-18 April 2007