Simulation Studies of a Trench MOS Device Structure with Small Figures of Merit

Junhong Li,H Bevrani,W Shuhui

doi:10.1051/matecconf/201820803005

Abstract

We proposed a vertical high permittivity trench power MOS (HKTMOS) device with alternating N&P drift region and high permittivity (HK) trench sandwiched in between. The unique structure guarantees uniform potential distribution for wide voltage range at block state owing to both HK potential modulation effect and superjunction (SJ) charge balance. The specific on-resistance (Rons) of HKTMOS is in orders of magnitude lower than the SJ counterparts at the on state because of the strong accumulation effect brought by HK trench. Although the gate charge also significantly rises because of the accumulation, the figures of merit (FOM) of HKTMOS still reduces considerably than the SJ under same BV. An expression for FOM is derived demonstrating that the FOM of HKTMOS is proportional to the square of HK trench depth, which agrees on with simulation results well. The simulation results indicate that within the BV range of 500~2000V, the Rons and FOM of HKTMOS are in 1~2 orders of magnitude lower and 17.4%~44.1% of SJ, respectively under the same BV condition. Furthermore, HKTMOS also demonstrates better charge imbalance tolerance than SJ.

Highlights

The performance of silicon power devices are essential for the energy conversion system
We propose a novel HK trench MOS (HKTMOS), which utilizes both potential modulation (PM) and carrier accumulation (CA) effects from HK, resulting in specific-Ron(Rons) decrease in orders of magnitude compared with conventional superjunction device (SJ)
Such Rons decrease is at the cost of larger switch loss due to the extra accumulation charge on the gate, the relationship between Rons and gate charge is linear, and the total figures of merit (FOM) of HKTMOS still experiences a significant improvement than the SJ

Summary

Introduction

The performance of silicon power devices are essential for the energy conversion system. The introduction of high permittivity (HK) material into power MOS device allows better potential distribution in silicon and improves device breakdown voltage (BV) [1]. We propose a novel HK trench MOS (HKTMOS), which utilizes both PM and CA effects from HK, resulting in specific-Ron(Rons) decrease in orders of magnitude compared with conventional superjunction device (SJ). Such Rons decrease is at the cost of larger switch loss due to the extra accumulation charge on the gate, the relationship between Rons and gate charge is linear, and the total figures of merit (FOM) of HKTMOS still experiences a significant improvement than the SJ. HKTMOS indicated strong doping-imbalance tolerance in N and P drift region

Device structure and mechanism

Findings

Simulation verification and discussion