Back-etched super-junction LDMOST on SOI

Abstract

Conventional super junction LDMOSTs (SJLDMOSTs), fabricated on an SOI substrate, suffer from low breakdown voltage due to substrate-depletion effects. In this work, a back etched SJLDMOST (BSJLDMOST) on SOI is proposed to overcome this problem by eliminating the silicon substrate under the device. The electrical characteristics of the BSJLDMOST on a 0.8 /spl mu/m SOI film were investigated. The device with 15.5 /spl mu/m of SJ region exhibits a breakdown voltage of 317 V, a specific on-resistance of 48.3 m/spl Omega/cm/sup 2/ and a charge on-resistance figure of merit of 4.1 /spl Omega/nC. To verify the back etching concept and the suppression of the substrate depletion effect, super-junction diodes (BSJDs) were implemented. These diodes feature a threefold improvement in breakdown voltage over conventional super junction diodes (SJDs) implemented without removing the silicon substrate on the back of the device. A discussion of how the BSJLDMOST can be optimized to break the silicon limit is also provided.