Detailed Study on Dynamic Characteristics of a High-Performance SGT-MOSFET With Under-the-Trench Floating P-Pillar

Abstract

We proposed a 150 V shielded-gate trench (SGT) power MOSFET with floating P-pillars under the trench and studied its static and dynamic characteristics, especially the transient capacitance and dynamic R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds(on)</sub> at high switching frequency. TCAD simulation demonstrated over 33% R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds(on)</sub> reduction compared with regular SGT-MOSFET. Up to MHz switching frequency, simulation indicates almost no R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds(on)</sub> increase in this device, meaning negligible dynamic R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds(on)</sub> penalty. On the other hand, elevated Coss is observed within a particular Vds range (40-90 V) as switching frequency increases, which translates to Qoss penalty. We investigated the underlying physical process for this Qoss change, and attributed it to the hole pilings in the undepleted region of the P-pillar. The overall parameters of this device, including R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds(on)</sub> and R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds(on)</sub> *Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oss</sub> , are superior to regular SGT-MOSFET and are close to superjunction MOSFET, which is more expensive and challenging in manufacturing. Although a 150 V MOSFET is used as our study vehicle, the analyses and conclusions apply to any power devices that employ the proposed device architecture.