A 1.2 kV-class superjunction (SJ) UMOSFET was realized using a multi-epitaxial growth method. The dynamic characteristics were characterized, and the potential of a product level device was identified for the first time. The switching characteristics with Schottky barrier diode showed no degradation in spite of the large drain-source capacitance (C DS ). The reverse recovery characteristics of the body diode exhibited a soft recovery which may originate from the large C DS and the short lifetime of minority carrier. A high short circuit capability comparable to a non-SJ device was demonstrated.

First Demonstration of Dynamic Characteristics for SiC Superjunction MOSFET Realized using Multi-epitaxial Growth Method

Power semiconductor devices are key to delivering high-efficiency energy conversion in power electronics systems, which is critical in efforts to reduce energy loss, cut carbon dioxide emissions and create more sustainable technology. Although the use of wide or ultrawide-bandgap materials will be required to develop improved power devices, multidimensional architectures can also improve performance, regardless of the underlying material technology. In particular, multidimensional device architectures—such as superjunction, multi-channel and multi-gate technologies—can enable advances in the speed, efficiency and form factor of power electronics systems. Here we review the development of multidimensional device architectures for efficient power electronics. We explore the rationale for using multidimensional architectures and the different architectures available. We also consider the performance limits, scaling and material figure of merits of the architectures, and identify key technological challenges that need to be addressed to realize the full potential of the approach. This Review examines the use of multidimensional architectures—such as superjunction, multi-channel and multi-gate technologies—in power electronics devices, exploring the performance limits, scaling and material figure of merits of the different architectures. 

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Multidimensional device architectures for efficient power electronics

In this paper, an improved 4H-SiC U-shaped trench-gate metal–oxide–semiconductor field-effect transistors (UMOSFETs) structure with low ON-resistance ( ${R}_{ \mathrm{\scriptscriptstyle ON}}$ ) and switching energy loss is proposed. The novel structure features an added n-type region, which reduces ON-resistance of the device significantly while maintaining the breakdown voltage ( ${V}_{\textsf {BR}}$ ). In addition, the gate of the improved structure is designed as a p-n junction to reduce the switching energy loss. Simulations by Sentaurus TCAD are carried out to reveal the working mechanism of this improved structure. For the static performance, the ON-resistance and the figure of merit (FOM $= {V}_{\textsf {BR}}^{\textsf {2}}/{R}_{ \mathrm{\scriptscriptstyle ON}}$ ) of the optimized structure are improved by 40% and 44%, respectively, as compared to a conventional trench MOSFET without the added n-type region and modified gate. For the dynamic performance, the turn-on time ( ${T}_{ \mathrm{\scriptscriptstyle ON}}$ ) and turn-off time ( ${T}_{ \mathrm{\scriptscriptstyle OFF}}$ ) of the proposed structure are both shorter than that of the conventional structure, bringing a 43% and 30% reduction in turn-on energy loss and total switching energy loss ( ${E}_{\mathbf {SW}}$ ).

An Improved 4H-SiC Trench-Gate MOSFET With Low ON-Resistance and Switching Loss

Owing to the superior properties of silicon carbide (SiC), such as higher breakdown voltage, higher thermal conductivity, higher operating frequency, higher operating temperature, and higher saturation drift velocity, SiC has attracted much attention from researchers and the industry for decades. With the advances in material science and processing technology, many power applications such as new smart energy vehicles, power converters, inverters, and power supplies are being realized using SiC power devices. In particular, SiC MOSFETs are generally chosen to be used as a power device due to their ability to achieve lower on-resistance, reduced switching losses, and high switching speeds than the silicon counterpart and have been commercialized extensively in recent years. A general review of the critical processing steps for manufacturing SiC MOSFETs, types of SiC MOSFETs, and power applications based on SiC power devices are covered in this paper. Additionally, the reliability issues of SiC power MOSFET are also briefly summarized.

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Review of Silicon Carbide Processing for Power MOSFET

The silicon carbide (SiC) super-junction JFET was designed, simulated and fabricated through trench-etching and sidewall-implantation technology, which avoids the expensive epi-regrowth process. The fabricated super-junction JFET achieves a breakdown voltage of 1000V with specific on-resistance of 1.3m $\Omega ~\cdot \text {cm}^{{2}}$ . The threshold voltage ( ${V}_{\text {th}}$ ) is stable over a wide range of temperature with less than 0.2V shift from 25°C to 175°C. These results demonstrate that the trench-etching and sidewall-implantation technology is a promising option to fabricate SiC super-junction devices. These devices could have great potential for future power electronics.

4H-SiC Super-Junction JFET: Design and Experimental Demonstration

We have fabricated Super Junction (SJ) V-groove trench MOSFETs (VMOSFETs), demonstrated a low specific on-resistance (R on A) of 0.97 mΩcm2 and a blocking voltage (V b ) of 820 V. In the first trial, SJ structure in 4H-SiC have proved to be a good combination with MOS interface on (0-33-8) faces which keep high channel mobility in high doping concentration. We designed a protection structure called “upper p-pillar region” and demonstrated that V b lowering appeared according to its width.

T. Masuda

Papers

0.97 mΩcm 2 /820 V 4H-SiC super junction V-groove trench MOSFET