“Various automotive chips are increasingly using silicon carbide (SiC) technology, which most chipmakers now consider a relatively safe bet to scramble to bring the wide-bandgap technology to the mainstream.

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Various automotive chips are increasingly using silicon carbide (SiC) technology, which most chipmakers now consider a relatively safe bet to scramble to bring the wide-bandgap technology to the mainstream.

Silicon carbide holds great promise in many automotive applications, especially electric vehicles. Compared with silicon, it can extend the driving range per charge, reduce the battery charging time, can provide the same range through lower battery capacity and lighter weight, and contribute to overall efficiency. The challenge now is to reduce the cost of manufacturing these devices, which is why SiC fabs are migrating from 6-inch (150mm) wafers to 8-inch (200mm) wafers.

“These compelling benefits are leading to massive adoption of SiC in electric vehicles, which reduces SiC manufacturing costs due to economies of scale,” said Victor Veliadis, executive director and chief technology officer of the PowerAmerica American Manufacturing Institute, established by the U.S. Department of Energy. “This is the main scale application that SiC manufacturers are focusing on, and it’s driving their manufacturing expansion. It’s also why many newcomers are entering the SiC space, and why we’re seeing intense competition for EV Design-win.”

Silicon carbide is finding its way into several electric vehicle systems, including traction inverters, DC-DC converters and onboard chargers, according to Veliadis, a professor of electrical engineering at North Carolina State University who manages PowerAmerica.

“High-voltage silicon carbide power devices are also key to enabling a fast-charging infrastructure that will remove the last major barrier to widespread consumer acceptance of electric vehicles,” he said. The charging time is similar in time.”

Following Tesla’s adoption of SiC in its main inverter in 2017, automotive has become a killer application for SiC, noted Ezgi Dogmus, principal analyst with Yole Développement’s compound semiconductor and emerging substrates team. “Since then, we have witnessed interest in SiC from almost all automakers and Tier 1 suppliers. BYD, Toyota and Hyundai have chosen SiC for their EV models, expect Audi, GM, NIO and Volkswagen And will follow suit.” Dogmus said, “With the significant increase in Design-Win of SiC solutions, we forecast a bright future for the period 2020 to 2026. In fact, the automotive market is undoubtedly the most important driver, so, By 2026, the automotive market will account for more than 60% of the total SiC device market share.”

In addition to electric vehicle applications, Dogmus also sees a trend towards the adoption of SiC in charging infrastructure, which can improve efficiency and reduce system size. In addition, silicon carbide is expected to grow at a double-digit CAGR between 2019 and 2026 in applications such as rail, motor drives, and photovoltaics.

Figure 1: Silicon Carbide Market Segmentation and Growth Forecast. Source: Yole Développement

Silicon Carbide and Gallium Nitride

Silicon carbide has significant advantages in power electronics compared to standard silicon products and other wide bandgap semiconductors such as gallium nitride (GaN).

“Silicon MOSFETs have experienced incremental growth and decades of improvement and are approaching their theoretical boundaries,” Dogmus said. “Historically, these MOSFET products have been adequate for their target applications. Meanwhile, silicon carbide and nitride Innovative wide-bandgap materials such as gallium exhibit performance characteristics that surpass silicon-based devices,” Dogmus said. “With high breakdown voltage, high switching speed, and small size, wide-bandgap materials are the most promising candidates to complement the power market industry. Additionally, they can reduce the number of passive components per system, enabling compact designs . However, these materials are still expensive compared to silicon.”

From a high-level perspective, the positioning of silicon, silicon carbide and gallium nitride is simple, said Robert Hermann, senior director and head of high-voltage conversion product marketing at Infineon Technologies. “Compared to silicon, silicon carbide is the strongest in terms of the combination of high temperature, high power and higher switching frequency. This is in line with the resulting system cost reduction for the main inverter and on-board charging.”

Gallium nitride is another major wide-bandgap technology with higher efficiency and improved frequency characteristics. “These two factors increase power density to a higher level compared to silicon carbide,” Hermann said. “However, unlocking this benefit requires greater system changes, as well as additional semiconductors and Passive products.”

Figure 2: Advantages of various technologies.Source: Infineon

For now, however, the real competition for SiC in EV and high-power system inverter applications is silicon, according to Yole’s Dogmus. “For silicon carbide, the price/performance ratio is attractive at higher voltages. For example, the adoption of 1,200V SiC devices in 800V battery vehicles will represent a significant market opportunity. At the same time, GaN will continue to penetrate rapidly into mobile phone applications. Charging market. In fact, at lower powers, GaN is more cost-effective than SiC. GaN is also expected to penetrate the datacom and telecom power markets, for systems less than 3kW, and in electric vehicle applications OBC and DC-DC converters.”

Figure 3: Silicon carbide product timeline.Source: Infineon

The advantages of silicon carbide outweigh the barriers

Not all testing and inspection processes are fully addressed, and the need for zero defects in automotive applications is a very high bar for any new material. But many semiconductor manufacturers believe these problems can be overcome relatively quickly and remain very bullish on the prospects for SiC chips in electric vehicles.

“While SiC power diodes have been used commercially for many years, SiC MOSFETs are rapidly changing the market landscape for SiC power electronics,” said Ming Su, technical marketing manager at ROHM Semiconductor. “One of the key drivers of recent market growth is electric vehicle power systems. Since the first adoption of SiC MOSFET technology in automotive traction inverters several years ago, the advantages of SiC over silicon devices in terms of energy efficiency and system size reduction have been Widely accepted by the automotive industry.”

Today, almost all automotive OEMs and EV startups have adopted silicon carbide, or are in the product design stage, using silicon carbide in EV traction inverters and onboard chargers, Su said. “Silicon carbide devices have also been used in fuel cell vehicles. Other automotive power converters using SiC include DC-DC converters that step down the battery voltage to 12V or 48V, and wireless chargers.”

Electric vehicles are currently experiencing a huge boom, driven by government regulations such as carbon dioxide emission limits set in the European Union and elsewhere. Infineon’s Hermann said: “This is also underscored by the strong desire to protect the environment, while still having a fun driving experience. This means increasing sales, going out of a large niche and into the future of the mass market for car production – ―And put more pricing pressure on OEMs. Silicon carbide plays a very important role in this context, as it supports various trends in electric vehicle power applications.”

This, in turn, opens up a long list of new options for OEMs and an equal number of opportunities for chipmakers.

“One of the technical advantages of silicon carbide compared to IGBTs is higher energy efficiency. Automotive inverters illustrate this well, where a few percent directly translates into longer range or smaller batteries,” Hermann said. . “With lower power losses, thermal management is simplified. This means that although pure power semiconductors cost more compared to IGBTs, SiC can significantly reduce system costs. For EV buyers, the formula is simple –Longer range at a lower cost.”

The efficiency of silicon carbide also means more interior space. “Silicon carbide can directly contribute to more space through another application, the on-board charger,” Hermann said. “To increase the range, the battery capacity increases. This means that the power level of on-board charging needs to increase, Otherwise, it is impossible to fully charge the battery overnight. In addition, more and more applications require bidirectional charging, such as vehicle-to-grid. Without design and technical measures, the on-board charger can become large, crowding out the space in the car Existing space. Using SiC, not only can the efficiency be improved, but higher switching frequencies can be achieved. This results in smaller passive components and less heat dissipation system. In fact, we believe that SiC can provide higher power density than conventional The silicon-based solution is doubled, enabling better design goals and reducing the size of onboard chargers.”

Automakers are turning to 800V DC buses to increase the amount of power available in vehicles and various applications without increasing the size of electrical connectors — which would add unnecessary weight and size to electric vehicles. For these applications, silicon carbide is more efficient than silicon and can reduce excessive heat loss.

“For an 800V bus, a SiC MOSFET rated at 1,200V is a suitable design choice, rather than using 650V, which is a more suitable choice for 400V batteries and systems.” Strategic Marketing, Innovation and Key, STMicroelectronics Power Transistors Division Project manager Filippo DiGiovanni said, “This means that SiC-equipped inverters are inherently more efficient, and the less stringent cooling requirements of silicon carbide are another big advantage. GaN transistors (or high electron mobility transistors, HEMTs) because they have a clearer efficiency advantage in high-voltage applications, such as traction inverters in electric vehicles, but SiC has better high-voltage characteristics than GaN with lateral structures.”

Bret Zahn, vice president and general manager of Onsemi Electric Vehicle Traction Power, said that silicon carbide is a key material for the next generation of semiconductors, providing technological advantages for silicon carbide power switching devices, significantly improving systems for electric vehicles, electric vehicle charging and energy infrastructure. efficient. “Silicon carbide power modules are a popular demand, but the SiC die segment is also growing rapidly.”

Higher voltage, lower total cost

The move to higher voltage architectures for fast charging has broad implications for electric vehicles.

Veliadis said: “At high voltages, the efficiency advantages of silicon carbide become more pronounced compared to their silicon counterparts. Today, almost all EV manufacturers design at 400V, and silicon is very competitive in this regard. By using higher voltages – such as 800 to 1,000V – thinner wires can be used, resulting in faster charging with less weight because higher voltages mean less current at the same power level .”

This helps cut costs and makes the entire system more efficient. “Electric vehicle customers want to see pricing comparable to internal combustion engines. More work is needed to get there,” he said. “In terms of SiC versus silicon pricing in EVs, the higher cost of today’s SiC devices is offset by the overall system simplification brought about by the benefits of SiC, including higher operating frequencies and reduced heat dissipation requirements. In addition, higher SiC Efficiency reduces the number of cells, which represents a significant cost for EVs. So overall, SiC in EVs is competitive and cheaper than silicon solutions. The main barrier to entry for large-scale SiC is Reliability and robustness issues, and a lack of trained developers to implement these technologies.”

He added that the value proposition of SiC will become even more pronounced as fast charging requires a higher voltage architecture to get the same power at lower currents (thus reducing weight, size and wiring costs).

To advance these technologies, OEMs are becoming more vertically integrated. This in turn puts pressure on tier 1 and tier 2 suppliers to further reduce costs. It also helps ensure an uninterrupted supply chain from wafer to automotive electronics suppliers to meet higher demand.

This has sparked a wave of investment in the SiC space, including some M&A activity. “Industry acquisitions are a trend,” Veliadis said. “In order for new entrants to compete effectively and in a timely manner with companies with long histories in SiC technology, synergies can be created by acquiring SiC companies that complement their expertise. And speed up time-to-market.”

Case in point: In August, Onsemi announced that it had reached a definitive agreement to acquire GT Advanced Technologies, a maker of silicon carbide (SiC) wafer growth technology and substrates.

“400V battery voltage is common today, but from 2024 onwards, there will be growing demand for 800V battery systems,” says Onsemi’s Zahn. “These systems are likely to become the standard because they don’t fit inside the car by increasing density and efficiency. Power distribution losses or increased cable size at charging stations, resulting in longer driving range per charge. At the 1,200V voltage rating required for an 800V bus, the advantages of SiC over silicon technology are even more pronounced. SiC can be used in more Operation at high switching frequencies and possibly higher temperature operation within packaging constraints. Given Tesla’s success with SiC and the need for higher range, many OEMs are eagerly pushing to implement SiC electric drivetrains.”

in conclusion

Government pressure to reduce emissions, coupled with the growing popularity of electric vehicles, is pushing silicon carbide and other wide-bandgap materials to the forefront. However, all of this will take time, and silicon carbide and gallium nitride have so far been the leading candidates to replace silicon in certain automotive applications.

Any new material comes at a cost in terms of yield, defects and various manufacturing processes, but SiC has enough advantages that OEMs can start designing it into various components of electric vehicles. Silicon carbide usage will grow year over year as the automotive industry pushes the technology into the mainstream, putting pressure on pricing and addressing possible fab issues.