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Meeting the demands of power electronics with silicon carbide

There has always been a need for power electronic components that manage the voltage and current delivered to a system. These components include inverters (DC to AC), rectifiers (AC to DC) and converters (both DC-DC and power factor correction). Users recognize many of these power components as large and heavy parts, such as the “brick” that is typically part of a computer power cord. For traditional applications like PCs, these components are mainly inconvenient for mobile users.

Now, though, power devices are emerging as critical enablers and drivers for the electronics industry. This is largely due to the rapid proliferation of electric vehicles (EVs), charging stations, and other applications in power generation and storage, such as photovoltaic (PV) and wind turbine installations and smart grid systems. As this new demand rapidly escalates, the technology behind power electronics has finally become a priority in the semiconductor industry.

Against this backdrop, silicon carbide (SiC) has emerged as the leading semiconductor material to replace Si in power electronics, especially newer, more demanding applications. In fact, recent market projections (Yole Développement, 2018) show the $300M market for SiC power devices growing to $1.5B in 2023—an astounding 31% CAGR over six years. Much of that growth comes directly from EVs, with revenue for power electronics in EVs and associated infrastructure (charging stations, etc.) growing from $19M to $566M. By 2023, over half of SiC power device revenue will come from EVs, PV and wind systems, with more growth to come.

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Figure 1. EV applications, the largest driver of growth in the SiC power device market, will account for 38% of the $1.5B market by 2023. (Yole Développement, 2018)

This tremendous ramp in SiC usage is driven not only by the expanding applications, but also by adoption of SiC over Si due to several inherent advantages. SiC has the same basic semiconducting behavior as Si or any other semiconductor material (gallium arsenide, gallium nitride, indium phosphide, etc.), but it has several properties that make it a superior option in power electronics. It delivers higher:

  • operating voltage range and switching speed due to higher bandgap energy;
  • efficiency and power density, due to higher conversion frequency and lower conduction loss;
  • voltage operation, due to significantly higher breakdown voltage;
  • operating temperature range, which increases power density due to reduced need for thermal management and heat sink requirements; and
  • thermal conductivity, which also results in higher power density.

These advantages of SiC over Si enable much more compact power electronic components due to efficiency and diminished cooling requirements, and they also extend the application space to higher voltage requirements. These benefits all contribute significantly to the use of SiC in EVs and other energy applications.

In EV applications, the use of SiC can extend vehicle range by up to 20%, significantly reducing power module weight and volume, relaxing cooling requirements, and enabling fast charging. Better acceleration and higher speed are further advantages of weight reduction. Smaller power electronics allow more functionality to be fit in the same form factor. Although SiC devices are still more expensive compared with Si-based devices, at the system level, the benefits of SiC technology are increasingly being appreciated by all players in the ecosystem—in turn, driving faster adoption.

The many benefits of SiC can only be realized with advances in SiC manufacturing. For many years, the SiC market has been plagued by an inconsistent and limited supply of high-quality wafers. It takes a highly controlled manufacturing process together with strong technology know-how to reduce or eliminate defects due to the kinetics of the SiC single-crystal growth process, specifically because there is no liquid phase of SiC. High-quality Si single-crystal boules are created with a process that solidifies pure silicon crystalline structures from the liquid phase. In addition, with the elevated temperatures and high voltage of power electronics operation, device reliability requirements continue to raise the bar on SiC wafer quality specs.

Finally, to reduce device cost and improve performance, the SiC industry is migrating from 100mm to 150mm wafers, which has further reduced the number of qualified suppliers worldwide. Compounding this technology trend with fast growth of the SiC device market, there is a severe short supply of high-quality 150mm SiC wafers.

Through recent mergers, the Compound Semiconductor Solutions business of Dow Corning—well known in the SiC market for its track record of developing and delivering high-quality 4H conductive SiC bare substrates and epi wafers—has become part of DuPont Electronics & Imaging. To cover a full range of applications, DuPont continues to supply SiC wafers in several quality grades, allowing fault-tolerant products to use more cost-effective SiC, while also providing higher-quality wafers for more demanding applications. Finally, we help our customers realize the advantages of a full-service manufacturer by providing SiC wafers (100mm and 150mm format) and SiC epitaxial wafers (100mm and 150mm).  As the opportunities for SiC described here continue to grow rapidly, we are currently investing in new capacity and manufacturing technology. 

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Figure 2. DuPont provides a complete range of SiC wafers (100mm and 150mm) and epitaxial wafers (100mm and 150mm).

The bottom line: Silicon carbide is taking off as a replacement for silicon in power devices due to significantly better device efficiency and system form factor. DuPont sees this opportunity and has continued to invest in SiC technology and manufacturing to maintain its spot as the leading supplier of high-quality SiC. 

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