For applications such as electric vehicles (EVs) and solar panels, engineers face a number of challenges as sensitive electronic components must continue to operate reliably in harsh environments. To further advance these sustainable solutions, innovations at the component level are needed to help improve overall system efficiency while providing greater robustness. Silicon carbide (SiC) semiconductors are quickly gaining attention as a technology that can enable these necessary advances.

 

What are SiC semiconductors?

 

As part of third-generation semiconductor technology, SiC solutions feature wide bandgap (WBG) characteristics and offer new levels of performance. The larger bandgap between the top of the valence band and the bottom of the conduction band increases the energy required for a semiconductor to switch from insulating to conducting compared to previous generations of semiconductors. In comparison, the energy values ??required for the transition for first and second generation semiconductors ranged from 0.6 eV to 1.5 eV, while the energy values required for the transition for third generation semiconductors range from 2.3 eV to 3.3 eV. In terms of performance, WBG semiconductors have a breakdown voltage ten times higher and are less activated by thermal energy. This means greater stability, enhanced reliability, better efficiency through reduced power losses, and a higher temperature ceiling.

 

For electric vehicle and inverter manufacturers who need outstanding high-power, high-temperature, and high-frequency performance, SiC semiconductors represent an exciting prospect. But how does this performance manifest in practice, and how can the semiconductor industry prepare to meet the potential demand?

 

 

SiC for Electric Vehicles

 

In electric vehicles and their supporting charging networks, high-performance semiconductors are at the heart of AC-DC charging stations, DC-DC fast chargers, motor inverter systems and automotive high-voltage DC to low-voltage DC transformers. SiC semiconductors will help optimize these systems, providing higher efficiency, higher performance ceilings and faster switching speeds, thereby reducing charging time and better utilizing battery capacity. This can increase the range of electric vehicles or reduce the size of batteries, thereby reducing vehicle weight and production costs, while improving performance and promoting wider adoption.

 

 

 

Although running cooler than their internal combustion engine-driven counterparts, electric vehicles are still an extremely harsh environment for power electronics, and thermal management is a key factor that designers must consider. For many early silicon and insulated gate bipolar transistor (IGBT) devices, the operating conditions within electric vehicles could cause them to fail during the vehicle's lifetime. Silicon carbide solutions have much higher thermal limits and an average thermal conductivity that is 3 times higher, making it easier to transfer heat to the surrounding environment. This improves reliability, reduces cooling requirements, further reduces weight and eliminates packaging concerns.

 

The increased peak voltage rating and surge capacitance enabled by SiC technology also supports manufacturers aiming to reduce charging times and reduce vehicle weight. Typically, most EV infrastructure runs between 200 V and 450 V, but automakers are taking performance a step further by increasing the voltage range to 800 V. The first to make the switch was the high-end Porsche Taycan, but more manufacturers are following suit with Hyundai’s recently released Ioniq 5, which now charges at 800 V and retails for a significantly lower price.

 

But what’s behind this shift? An 800 V system offers a variety of benefits, such as faster charging times, reduced cable size (due to lower currents), and reduced conduction losses, all of which help save production costs and improve performance. Currently, fast-charging systems rely on expensive water-cooled cables, which can be eliminated, while inside the vehicle, smaller gauge cables can significantly reduce weight and increase the vehicle’s range. For some manufacturers, getting the performance gains needed to convince consumers to adopt electric vehicles requires a voltage increase to 800 V, but this development is only possible through the use of silicon carbide semiconductors. Existing second-generation semiconductors simply do not have the performance and reliability required to operate at such high voltages in the harsh environment of electric vehicles and their charging infrastructure.

 

Silicon carbide for sustainable power generation

 

In addition to electric vehicles, the performance of this new generation of silicon carbide semiconductors will benefit many more growing industries. Renewable energy is expanding rapidly, so solar/wind farm inverters and distributed energy storage solutions (ESS) that rely on semiconductor technology are expected to experience compound annual growth rates (CAGR) of 13% and 17% respectively. Rapid growth. (Source: "Global Solar Central Inverter Market Report 2022-2026")

 

Similar to increasing vehicle voltage in the electric vehicle industry, SiC technology also enables solar farms to increase string voltage. Existing installations typically operate at voltages between 1000 V and 1100 V, but new central inverters using SiC semiconductors can operate at voltages up to 1500 V. This reduces the size of the string cables (because the current is lower) and the number of inverters. Because each device can support more solar panels, one of the larger hardware expenses in a solar farm, reducing the number of inverters and cable size can significantly reduce overall project costs.

 

SiC technology brings benefits to renewable energy applications beyond supporting higher voltages. For example, onsemi’s 1200 V EliteSiC M3S MOSFETs reduce power losses by up to 20% in hard-switching applications such as photovoltaic inverters compared to industry-leading competitors. This saving has a considerable impact when the scale of operations is taken into account (there are 208.9 GW of solar farms in Europe alone). (Source: Global Centralized Photovoltaic Inverter Market Report 2022-2026)

 

Solar farms and offshore wind are challenging environments for electrical components in terms of reliability, and it is in these environments that SiC technology will once again outperform existing solutions. By supporting higher temperatures, voltages, and power densities, engineers can design systems that are more reliable, smaller, and lighter than existing silicon solutions. The enclosure of the inverter can be shrunk, and many of the surrounding electronics and thermal management components can be eliminated. And SiC's support for higher frequency operation allows for smaller magnets, further reducing system cost, weight, and size.

 

Challenges in Semiconductor Production

 

It is clear that SiC semiconductors represent an improvement in almost every way for electric vehicles and sustainable energy generation. Using good SiC MOSFETs and diodes can make the entire system operate more efficiently while reducing design considerations and, in many cases, the cost of the entire project. However, as with any pioneering technology, there will be a huge demand. One question facing many electronic engineers is whether SiC manufacturing is ready for widespread adoption and whether production will remain reliable as volumes increase.

 

Fundamentally, one of the main issues facing SiC is the process by which it is prepared. Silicon carbide exists in large quantities in space, but is very rare on Earth. Therefore, silicon carbide needs to be synthesized from silica sand and carbon in a graphite furnace at temperatures between 1600°C and 2500°C. This process produces a block of silicon carbide crystals, which then need to be further processed to eventually form a silicon carbide semiconductor. Each production step requires extremely strict quality control to ensure that the final product meets strict testing standards. To ensure quality, Onsemi Semiconductor uses a unique approach. As the only end-to-end silicon carbide manufacturer in the industry, they control every production step from substrate to final module.

 

In their factories, silicon and carbon are combined in furnaces, then processed by CNC machines into cylindrical disks, which are then sliced into thin wafers. Depending on the desired breakdown voltage, specific epitaxial wafer layers are grown before the wafers are cut into individual dies and packaged. By controlling the entire process from start to finish, Onsemi Semiconductor has been able to create a very efficient production system to prepare for the growing demand for SiC.

 

 

 

Although Onsemi Semiconductor has leveraged its experience in the production of silicon-based technologies, there are many unique challenges associated with SiC materials to ensure high quality and robustness of the final product. For example, in order to produce a reliable final product, many aspects of the existing industry standards designed for silicon technology need to be exceeded. Through extensive collaboration with universities and research centers, Onsemi Semiconductor was able to determine the characteristics and reliability of SiC under a variety of conditions. The result is a comprehensive and integrated approach that can be applied to all of Onsemi Semiconductor's SiC production processes.

 

Silicon Carbide - The Right Technology at the Right Time?

 

Energy efficiency, reliability and cost-effectiveness are key factors for sustainable technologies to have the necessary impact on the real world and help us achieve global climate goals. It used to be nearly impossible to find component-level solutions that could meet all three of these goals, but for many applications, that’s exactly what SiC technology can deliver. While global supply shortages have slowed the adoption of silicon carbide semiconductors somewhat, it’s clear that we’ll now see rapid advancement of the technology.

 

There will still be some challenges to mass adoption of SiC, such as semiconductor manufacturers keeping up with demand and ensuring reliability. But through collaboration and research, such as that conducted by Onsemi, the industry should be able to ensure that high standards are maintained and manufacturing efficiency is optimized. When it comes to deployment, it’s important to remember that first- and second-generation semiconductors still have their place. For some applications, such as logic ICs and RF chips, SiC’s high performance may not be appropriate, but for applications such as electric vehicles and solar, SiC technology will prove to be transformative.

 

 

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