Yoshito Nakazawa

Vertical charge imbalance effect on 600 V-class trench-filling superjunction power MOSFETs

600V-class superjunction (SJ) MOSFETs fabricated by trench-filling process are investigated by analytical and numerical solutions with experimental results. The careful consideration on the effects of trench taper and p-column profile is given for accurate charge control. The breakdown voltage (Vb), specific on-resistance (RonAa), and gate-to-drain charge (Qgd) of 736 V, 16.4 mΩ-cm2, and 6 nC, respectively, have been achieved for the fabricated SJ-MOSFET.

On the scaling limit of the Si-IGBTs with very narrow mesa structure

The very narrow mesa structures based on our 7th generation IGBT process are fabricated and it is found that the device with the narrowest mesa shows very poor short circuit (SC) withstand capability although it suppresses the conduction loss considerably. This poor SC capacity is caused by non-saturated output characteristics which are originated by collector bias induced barrier lowering in the middle of Si mesa. The current filamentation is observed in the 3D multi-cell short circuit simulation with self-heating and the SC capacity degradation due to the filamentation is enhanced in the narrower mesa structure.