Accelerated Life Test for SiC Schottky Blocking Diodes in High-Temperature Environment

This paper reports on the life tests of silicon carbide Schottky diodes with high-temperature operation capability (up to 270degC). These 300-V-3-A diodes have been designed to meet the BepiColombo requirements, a European Space Agency mission to Mercury. The life test consisted in a dc current stress of 5 A applied to these diodes at 270degC for 600 h or more. Different diode technologies have been tested and compared. On typical Ti or Ni Schottky diodes with thick aluminum metal layer, these reliability tests revealed degradation at both the Schottky interface and the diode top surface due to aluminum diffusion. The use of W as Schottky metal allows eliminating the forward voltage drift producing stable metal-semiconductor interface properties. The use of thick gold metallization allows reducing the surface and bonding degradation. The final diodes demonstrated high stability at 270degC.