Improved Device Characteristics Obtained Using a Novel High-K Dielectric Stack for 4H-SiC n-IGBT: HfO2-SiO2- AlN

We report on a novel method of stacking multiple oxide layers on 4H-SiC 20 kV IGBT. Instead of SiO2/SiC interface which is common for any SiC based MOS device, we found that the AlN/SiC interface would yield better results. We have performed 2D numerical simulations to analyze static characteristics for three combinations of dielectric stacks on IGBT: HfO2-SiO2, HfO2-AlN, and HfO2-SiO2-AlN (by maintaining the same equivalent oxide thickness value). In addition to higher transconductance (gm) and lower subthreshold swing (SS), the device with AlN/SiC interface offer comparatively lower RSP,ON and higher mobility with respect to temperature. Nevertheless, with a partial compromise on device characteristics improvement, insertion of SiO2 in the dielectric stack helps in suppressing the subthreshold current owing to higher band offset with respect to SiC. The turn off characteristics of the device is analysed using a clamped inductive circuit. Device with AlN/SiC has shown better dIc/dt and fall time compared to SiO2/SiC interface.