Safe Operating Area Considerations for Integrated Trench-Based Power Devices

This paper discusses the hot-carrier and electrical safe operating area (SOA) of trench-based integrated power devices. The hot-carrier SOA is determined by the avalanche current, exhibiting a maximum at intermediate drain voltage. The initial hot-carrier degradation is dependent on the crystal plane on which the gate oxide is grown. During hot-carrier stress, interface states are formed in the device´s accumulation region. No channel degradation is observed. The electrical SOA of the trench-based MOS (TB-MOS) is much larger than a comparable lateral DMOS (LDMOS) or vertical DMOS (VDMOS). Even for 100-ns pulses, the TB-MOS exhibits electrothermal effects, contrary to LDMOS and VDMOS. Finally, the intrinsic gate oxide quality of the trench gate oxide is reported on. It is proven that the oxide time-dependent dielectric breakdown is determined by the thinnest oxide along the trench sidewall.