Tutorials

Devices

Fundamentals of SiC Power Devices

Prof. Victor Veliadis

PowerAmerica / North Carolina State University, USA

Abstract

There are several reasons behind silicon's dominance of the power device market. Silicon is renowned for its excellent starting material quality, streamlined fabrication, opportunity for low-cost mass production, proven reliability, and circuit design legacy. However, despite significant progress, silicon devices are now approaching their operational limits. They are held back by their relatively low bandgap and low critical electric field, traits that result in high conduction and switching losses, and substandard high-temperature performance.

In this tutorial, the favorable material properties of Silicon Carbide (SiC), which allow for highly efficient power devices with reduced form-factor and cooling requirements, will be summarized. The co-existence of Si, SiC, and GaN will be discussed, and their respective competitive application advantages highlighted. The tutorial will highlight design aspects of diodes, JFETs, and planar and trench MOSFETs, which are presently being inserted in most SiC based power electronic systems. Material and device fabrication aspects will be presented with an emphasis on the processes that do not carry over from the mature Si manufacturing world and are thus specific to SiC. The nine to tenfold increase in critical electric field strength of SiC over that of Si allows high voltage blocking layers to be fabricated significantly thinner than those of similarly rated Si devices. However, the lack of a well-designed edge termination structure can diminish the high voltage performance of SiC power devices due to electric field crowding. Consequently, specialized edge termination structures are utilized to maximize breakdown voltage, and will be discussed.

Biography

Dr. Victor Veliadis is Executive Director & CTO of PowerAmerica, a member-driven Department of Energy (DOE) Manufacturing USA Institute of industry, universities, and national labs accelerating the commercialization of energy efficient silicon-carbide and gallium-nitride power semiconductor chips and electronics. At PowerAmerica, he has managed a budget of $156 million, which he strategically allocated to 212 industrial and university projects to catalyze SiC and GaN semiconductor and power electronics manufacturing, workforce development, and job creation. His PowerAmerica educational activities have trained 430 full-time university students in collaborative industry-university wide bandgap projects, and engaged over 8000 attendees in tutorials, short courses, and webinars. Since 2024, Dr. Veliadis has been managing a $64M DOE renewal to further catalyze WBG power technologies.

Dr. Veliadis is a professor at NC State University's Department of Electrical and Computer Engineering, an IEEE Fellow, a National Academy of Inventors (NAI) Fellow, and an IEEE Electron Device Society Distinguished Lecturer. He has 27 issued U.S. patents, 13 book chapters, one co-edited book, and 173 peer-reviewed publications to his credit. Prior to entering academia and taking an executive position at PowerAmerica in 2016, Dr. Veliadis spent 21 years post-Ph.D. in the semiconductor industry, where his work included design, fabrication, and testing of SiC devices, GaN devices for radar systems, and financial and operations management of a commercial semiconductor fab. He has received military training in the Army Infantry and is a third-degree black belt in Shotokan karate. Dr. Veliadis earned a Ph.D. in Electrical Engineering from Johns Hopkins University (1995).

Packaging

Sintered joining for power devices − Microstructural analysis and local mechanical property evaluation

Prof. Tomoki Matsuda

Division of Materials and Manufacturing Science, Graduate School of Engineering, The University of Osaka, Japan

Abstract

The increasing use of wide-bandgap (WBG) power devices based on SiC and GaN has created a need for die-attach materials capable of operating at higher junction temperatures and under demanding thermal and power-cycling conditions. Sintered silver (Ag) and copper (Cu) joints are promising alternatives to conventional solders because of their high thermal stability and excellent thermal and electrical conductivity. However, these joints contain pores and heterogeneous microstructures, and their overall mechanical reliability is strongly influenced by local deformation and fracture at particles, necks, pores, and interfaces. Such local behavior is difficult to evaluate using conventional macroscopic testing alone.

This tutorial introduces an approach for characterizing sintered joints as hierarchical and heterogeneous materials. Nano- and micro-scale microstructural observations are combined with local mechanical testing to evaluate the strength, deformation, and fracture behavior of individual microstructural regions and interfaces. Case studies on Ag and Cu sintered joints are used to illustrate how processing conditions affect microstructure and how these microstructural features influence local mechanical response. The tutorial also discusses how process, microstructure, and local mechanical properties can be related quantitatively. These relationships can support the interpretation of macroscopic joint behavior and help identify the microstructural regions that govern deformation and fracture. The presented framework is intended to provide materials researchers and packaging engineers with practical tools for evaluating and improving the reliability of sintered die-attach joints for power-device applications.

Biography

Tomoki Matsuda is an associate professor at the Division of Materials and Manufacturing Science, The University of Osaka since 2015. He obtained a Ph.D. from the University of Osaka in materials science and engineering, specialized in shock-matter interaction using ultrashort laser processing. He has engaged in hierarchical control of dissimilar interface and mechanism of its properties for reliable dissimilar materials joining process, including electronics packaging. He has participated in national projects on research and development of welding and joining processes for innovative structural materials which includes improvement of dissimilar joints by controlling nano- to mesoscale interfacial structure, development of multiscale characterization methods including in situ observation of fracture of joints using electron imaging and synchrotron radiation. These achievements were recognized in scientific communities and he was awarded more than 10 prizes.

Applications

Pushing Solid-State Pulsed Power Beyond 10 kV: Series-Connected SiC MOSFETs and Advanced Applications

Dr. Takafumi Okuda

NexFi Technology Inc. / The University of Osaka, Japan

Abstract

SiC power devices offer fast switching, high-frequency operation, and high power capability. Currently 1-kV-class SiC power devices are commercially available and widely used in industrial applications. Extending these advantages to voltage levels beyond 10 kV, however, requires advanced circuit and packaging technologies.

This lecture introduces a practical approach to achieving high-speed switching beyond 10 kV using series-connected, commercially available SiC MOSFETs. It covers the basic concept of series-connected power devices, key challenges in high-voltage switching, and the development of original water-cooled high-voltage SiC power modules for high-power and high-frequency operation.

The lecture also presents several applications of this technology, including plasma generation, insulation testing with fast voltage pulses, and pulsed-power systems for particle accelerators. These examples demonstrate how SiC devices can open new possibilities for high-voltage and high-speed power electronics, particularly for solid-state pulsed-power applications.

Biography

Takafumi Okuda received his Ph.D. degree from Kyoto University in 2015 for his research on the characterization of SiC crystals and the fabrication of SiC power devices. He then joined the Department of Electrical Engineering at Kyoto University, and his research focus was on the study of power electronic circuits utilizing SiC power devices. In 2020, he joined Osaka University to further his research on ultra-high-voltage circuits using SiC power devices. Currently, he holds the position of Specially-appointed Associate Professor at Osaka University, and he is also actively engaged in NexFi Technology Inc.

Dr. Okuda is a member of the Japan Society of Applied Physics (JSAP), the Institute of Electrical Engineers of Japan (IEEJ), and the Institute of Electrical and Electronics Engineers (IEEE).