Xiaoping Dai

Silicon carbide split-gate MOSFET with merged Schottky barrier diode and reduced switching loss

A silicon carbide split-gate MOSFET (SG-MOSFET) is proposed in this paper, which features a Schottky barrier diode embedded above the JFET region between the split gates. Therefore, the proposed SG-MOSFET boasts a unipolar reverse conduction path with low turn-on voltage. Additionally, the gate-to-drain charge in the proposed device is greatly reduced, owing to the presence of the Schottky anode that is shorted to the source contact. The influence of key device parameters has been studied via device simulation using Sentaurus TCAD. Comprehensive comparisons between the proposed SG-MOSFET and the conventional MOSFET are made. Apart from the superior reverse conduction characteristics, the SG-MOSFET exhibits a significant lower switching loss thanks to both the low gate-to-drain charge and the elimination of charging/discharging currents for external freewheeling diodes.

SiC Trench MOSFET With Shielded Fin-Shaped Gate to Reduce Oxide Field and Switching Loss

A silicon carbide shielded fin-shaped gate metal-oxide-semiconductor field effect transistor (SF-MOS) is proposed in this letter, which utilizes a well-grounded p-region to shield the fin-shaped trench gate. Numerical simulations by Sentaurus TCAD are carried out to study the performance of SF-MOS, and comparisons with conventional trench MOSFET and the state-of-the-art double-trench MOSFET are presented. The maximum electric field in gate oxide of the SF-MOS is effectively lowered to below 3 MV/cm, which is a widely accepted criterion for long-term gate oxide reliability. Furthermore, with the shielding effects, the gate-to-drain charge of the SF-MOS is significantly reduced, leading to lower switching loss.

Mitigation of challenges in automotive power module packaging by dual sided cooling

Packaging of power semiconductor modules is facing huge challenges from automotive customers in terms of performance, temperature, reliability, weight, volume and cost etc. It is believed that choice of the power module structure, material and assembly technology are key factors for mitigating the challenges. Among them, the cooling structure and of the module is of most importance to address these issues. In this paper, the dual sided cooling module for Hybrid and Electric Vehicles (HEV/EV) is proposed as an effective methodology for addressing these automotive level challenges. It is found that the thermal performance is improved significantly by cooling the module on both sides, which enhances the electrical performance at high power, high switching speed and improves thermal stability. The electrical performance and reliability are further improved by wire bondless interconnection and ultrasonic welding of power terminals. By eliminating the baseplate in the module, the weight, volume and cost are reduced accordingly.

SiC MOSFET with built-in SBD for reduction of reverse recovery charge and switching loss in 10-kV applications

A silicon carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET) for 10-kV application is proposed in this paper, which features a built-in Schottky barrier diode (SBD). Therefore, the body diode is free from activation during the third quadrant conduction state, which is beneficial for reducing the switching loss and suppressing bipolar degradation. Numerical simulations with Sentaurus TCAD are carried out to investigate the characteristics of the proposed structure in comparison to the conventional MOSFET and SBD pair. It is found that the proposed structure achieves lower reverse recovery charge and switching loss owing to three factors, i.e., faster switching speed, smaller capacitive charge, and body diode deactivation, and therefore is a superior choice for 10-kV applications.

Improved surge current capability of power diode with copper metallization and heavy copper wire bonding

Copper metallization and copper wire bonding of high power semiconductor devices have attracted growing attention in recent years due to potentially much improved reliability and increased lifetime. However, significant technical challenges still remain for its wide commercial use. Here a thick copper layer has been successfully grown onto 3300V fast recovery diodes and subsequently 16mil copper wires were used to bond the chips onto substrates. Much improved surge current performance of these copper metallized and heavy copper wire-bonded diodes over its aluminium counterpart is reported here, and the results are analysed with the help of simulation.

Effect of Design Variations and N2O Annealing on 1.7kV 4H-SiC Diodes

In this work we have studied the influence of design and process variations on electrical performance of 1.7 kV 4H-SiC Schottky diodes. Diodes with two variations in their active region design namely, stripe design and segment design, were fabricated in this study. Field Limiting Rings (FLRs) or Junction Termination Extension (JTE) were used as edge termination design to achieve a blocking voltage of 1.7 kV. In addition to these designs an extra processing step of nitrous oxide (N2O) annealing was performed on some of the diodes. The study has shown that there is no extra beneficial effect of nitrous oxide annealing on device characteristics.

A novel 1700V RET-IGBT (recessed emitter trench IGBT) shows record low V CE(ON) , enhanced current handling capability and short circuit robustness

In this paper, a novel 1700V recessed emitter trench IGBT (RET-IGBT) is proposed. The RET-IGBT features an additional recessed trench between two adjacent active trenches and under the emitter contact, which reduces the drawn trench to trench separation from 6μm to 2μm. Combined with a double-dose carrier storage (CS) layers, the injection enhancement effect is enhanced. As a result, the trade-off relationship between Vce(on) and £off is improved. The fabricated RET-IGBT shows record low Vce(on) of 1.65V at 150A(110A/cm−2), no degradation in breakdown voltage and short circuit performances whilst enhancing the current handling capability in spite of increased current density.

Status and Trend of Power Semiconductor Module Packaging for Electric Vehicles

Power semiconductor modules are the core components in power-train system of hybrid and electric vehicles (HEV/EV). With the global interests and efforts to popularize HEV/EV, automotive module has become one of the fast growing sectors of power semiconductor industry. However, the comprehensive requirements in power, frequency, efficiency, robustness, reliability, weight, volume, and cost of automotive module are stringent than industrial products due to extremely high standards of vehicle safety and harsh environment. The development of automotive power module is facing comprehensive challenges in designing of structure, material, and assembly technology. In this chapter, the status and trend of power semiconductor module packaging for HEV/EV are investigated. Firstly, the functionality of power electronics and module in HEV/EV power-train system, as well as the performance requirements by automotive industry, is addressed. A general overview of HEV/EV module design and manufacturing is discussed. Then, the typical state-of-the-art commercial and custom HEV/EV power modules are reviewed and evaluated. Lastly, the packaging trends of automotive module are investigated. The advanced assembly concept and technology are beneficial to thermal management, minimized parasitic parameters, enhancement of thermal and mechanical reliability, and the reduction of weight, volume, and cost.