A Charge Balanced Vertical Power MOSFET with Record High Balliga’s Figure of Merit: Design and Investigation

Hafsa Nigar,Hend I Alkhammash,Sajad A Loan

doi:10.1007/s12633-021-01141-0

Abstract

In this work, we design and simulate a high-performance vertical power MOSFET with a charge balanced drift layer, which modulates the RON-BV relation from super quadratic to linear. The proposed device is designed with a super junction drift layer which modulates the RON-BV relation from super quadratic to linear. The proposed device has the source and channel regions isolated from the super junction drift layer. This results in a significant improvement in the performance of the proposed device in comparison to the other conventional devices, in terms of Balliga’s figure of merit. A 2D TCAD simulation study reveals that the proposed device with an epitaxial layer thickness of 50 μm shows an ON resistance of 3.84mΩ.cm2 for a break down voltage of 833 V, which is the lowest among the resistances reported in the previous literature at this breakdown voltage. Further, the study of charge imbalances and the capacitance analyses including the calculation of gate charge has also been done. The values of Balliga’s figure of merit (FOM) calculated for all the drift thicknesses of the proposed structures are significantly outperforming the conventional super junction structures reported so far.

Highlights

Power devices find applications in almost all domains with power consumption of a few watts to tens or hundreds of watts to kilo Watt (KW) or megawatt (MW) applications, such as traction for cars and trains etc [1]
The vertical power devices carrying voltage sustaining layer encounters a prominent limitation between its breakdown voltage and ON state resistance, which is defined by the relation [15]
The proposed device uses two laterally aligned poly silicon buried gates, along with the super junction drift layer consisting of a single n-type doped silicon column sandwiched between two P doped silicon columns each with a width equal to the half of the n column width

Summary

Introduction

Power devices find applications in almost all domains with power consumption of a few watts (mobile phones and portable devices) to tens or hundreds of watts (computer) to kilo Watt (KW) or megawatt (MW) applications, such as traction for cars and trains etc [1]. A novel vertical power MOSFET structure with charge balance drift region is proposed showing reduced ON resistance and a good immunity of breakdown voltage towards p-body doping variations. The simulation results have shown that the breakdown performance of the proposed device does not differ, when the p-body doping is reduced to reduce the ON resistance.

Results

Conclusion