Electric vehicles are rushing to grab SiC, why is this?

With the maturity of SiC products and technologies, its application expansion in the field of electric vehicles is not only reflected in the expansion of penetration scope, but also in the deepening of application methods. In the early electric drive inverters of new energy vehicles, a hybrid architecture of Si-based IGBTs and SiC-SBDs is generally used, and it is currently evolving to pure SiC inverters.

Not long ago, Groupe Renault and STMicroelectronics announced that they have reached a cooperation agreement on the supply of SiC (silicon carbide) and GaN (gallium nitride) products for new energy vehicles from 2026 to 2030. Coincidentally, earlier this year, Germany’s Vitesco Technologies also won an order from Hyundai Motor for hundreds of millions of euros of 800V SiC inverters; JAC and Bosch also signed a cooperation agreement in the field of SiC inverters The strategic agreement of…

In the field of SiC, the recent actions of other leading electric vehicle companies and new car manufacturers are also attracting attention. For example, Tesla released a new model Model S Plaid using SiC inverters; BYD also announced that it will achieve SiC automotive power by 2023 when it launched the first model with SiC technology, “BYD Han”. A comprehensive replacement of silicon (Si)-based IGBTs by semiconductor devices; NIO also stated that it will adopt an electric drive system based on SiC technology on the new ET7 model delivered in 2022.

There are various indications that in the next few years, SiC power devices will usher in a small market upsurge in the field of electric vehicles, so everyone is planning ahead and laying out “pairs” in advance to make their own supply chains more robust.

Why use SiC?

In fact, considering the cost of electric drive inverters for electric vehicles, if SiC power devices are used to replace mature Si-based IGBTs, the cost of a single vehicle will increase by 200 to 300 US dollars, so why are people willing to spend more to adopt this technology? What about the “expensive” plan? This has to start with the characteristics of the SiC device itself.

In the field of power electronics, the power device responsible for switching control is the key to performance. For a long time, Si materials have dominated this field, but with the increasing power density in applications, higher switching speeds (frequency), and more stringent power consumption requirements, the performance of Si devices is “squeezed”. It is also getting closer and closer to its theoretical limit, so people start to look for new semiconductor materials that can replace Si. As a result, two wide-bandgap semiconductor (also known as third-generation semiconductors) materials, SiC and GaN, have gradually entered people’s field of vision, and SiC has many characteristics in power semiconductor devices ranging from 650V to 3.3kV. Unparalleled advantage.

Electric vehicles are rushing to grab SiC, why is this?
Figure 1: Performance and application range of devices with different semiconductor materials (Image source: Infineon)

As shown in Figure 2, the forbidden band width of SiC is 3 times that of Si, the dielectric breakdown field strength (critical field strength) is nearly 10 times that of Si, the thermal conductivity is 3 times that of Si, and the electron saturation mobility is 2 times that of Si. times…these characteristics in power devices mean:

・ High forbidden band width: The larger the forbidden band width, the higher the critical breakdown voltage, which is more suitable for high voltage and high power applications.
・ High saturation electron mobility: The higher this value, the faster the switching speed of the device, resulting in less drive power and lower energy loss for high frequency operation at high voltage. Moreover, the use of smaller peripheral devices in high-frequency circuits also contributes to the miniaturization of the system.
・ High thermal conductivity: can avoid the use of additional cooling system, which is conducive to the optimization of cost and form factor.
・ Small on-resistance per unit area: It can effectively reduce losses.

Electric vehicles are rushing to grab SiC, why is this?
Figure 2: Comparison of key properties of different semiconductor materials (Image credit: Infineon)

Specific to automotive applications, some analysis shows that replacing Si-based devices with SiC devices in electric drive inverters can reduce the energy efficiency loss of drivers at the device level by 80%. According to Cree’s estimates, the use of SiC power devices in electric vehicle inverters can reduce vehicle power consumption by 5%-10%. Taking into account, although the cost of inverter modules will increase, the cost of batteries, heat dissipation The cost, as well as the cost of space use, will be significantly reduced, and the cost of the whole vehicle can be saved by about 2,000 US dollars. In addition to inverters, SiC power devices can also be used in many aspects such as on-board chargers (OBC) and power conversion systems (DC/DC) of electric vehicles.

Tesla’s success

In fact, everyone has long known the above-mentioned performance advantages of SiC devices, but if these discussions only stay at the theoretical level without actual successful cases, it is inevitable that people will be hesitant when making technical decisions. Therefore, today, the reason why many car companies can make a decisive decision to “embracing” SiC is that in addition to the technological progress of SiC itself in recent years, Tesla’s demonstration role should not be underestimated.

In terms of adopting SiC power devices in electric vehicles, Tesla should be the first full-car company to “eat crabs”. In 2018, Tesla used the 650V SiC MOSFET launched by STMicroelectronics on the inverter of Model 3. It is said that compared with the earlier models such as Model X using Si-based IGBT, this move can bring more benefits to the inverter. The efficiency improvement of 5%-8% is indispensable for improving the battery life of the vehicle. Then, on the Model Y launched in 2020, Tesla also used SiC MOSFETs in the rear-wheel drive of the power module. In addition to the Model S Plaid mentioned above, Tesla has now reached 3 models using SiC technology. Among them, with the better high-voltage, high-temperature, and high-frequency performance provided by SiC MOSFET for the electric drive inverter, the Model S Plaid only needs 2.1 seconds to accelerate from 100 kilometers to 100 kilometers. “Label” has undoubtedly become the best endorsement of SiC.

With the maturity of SiC products and technologies, its application expansion in the field of electric vehicles is not only reflected in the expansion of penetration scope, but also in the deepening of application methods. In the early electric drive inverters of new energy vehicles, a hybrid architecture of Si-based IGBTs and SiC-SBDs is generally used, and it is currently evolving to pure SiC inverters. In 2017, Rohm’s pure SiC power modules helped the VENTURI team to create a new inverter, which was reduced by 43% in size and 6kg in weight. Such successful cases make the future of pure SiC inverters very promising. expect.

Will there be a lack of fashion?

According to the forecast of HIS Markit, the market size of SiC power devices is expected to exceed US$10 billion by 2027, with a compound annual growth rate of nearly 40% from 2018 to 2027! Among them, the new energy vehicle market is a major driving force.

However, the increase in demand will also bring about a worry, that is, “whether the outbreak of demand will cause a shortage of supply”, especially in the past two years, the automotive electronics field has suffered from “lack of cores”, and the psychological shadow has not yet dissipated. Everyone’s concern about this has gone a step further.

From the current point of view, the factors restricting the rapid expansion of SiC device production capacity mainly include:

・ SiC is still difficult to compare with Si in the preparation of basic materials such as substrate wafers and epitaxial wafers. For example, substrate wafers are mostly 4 inches and 6 inches (while the mainstream processes of Si devices are 8 inches and 12 inches); vapor phase epitaxy Low rates, low liquid phase epitaxy yields… Until there are breakthrough solutions to these technical problems, capacity is bound to be limited.

・ From the SiC device manufacturing process, how to form a good ohmic contact in the production of electrodes is still a difficult point.

・ From the layout of the SiC industry chain, in the past, key process technologies were in the hands of a few companies, and the entire market was small, and it was far from forming a large division of labor based on standardization like Si-based processes.

The above bottlenecks will restrict the rapid ramp-up of production capacity and the reduction of costs. Taking SiC substrate wafers as an example, the current cost of SiC is 4 to 5 times that of Si, and it is expected that the price will gradually drop to about 2 times that of Si in the next 3-5 years. In this process, it may be inevitable that production capacity and supply will be tight in the short term.

Fortunately, the good expectations for the development of the market have brought sufficient confidence to everyone, so it can be seen that the industry’s investment in increasing production capacity is also increasing, such as STMicroelectronics’ acquisition of Norstel, Infineon’s The acquisition of Siltectra, an emerging company in the field of SiC wafer dicing, etc.

What kind of reasonable prediction should you have for the development of SiC devices in the future? The previous opinion of a person in the industry is relatively objective, and we may wish to quote it here – IGBT has developed for 30 years since 1990, and has gone through 7 generations of technology, and the final cost has been reduced to one-fifth of the original; The development of SiC from an emerging technology to a general technology will also be a very long process, and SIC technology also needs time to be technically polished.

Therefore, for SiC, on the one hand, we must actively follow this general trend, and on the other hand, “patient” is also necessary. If we grasp this rhythm, the entire technology upgrade will be more seamless and smoother.

Author: Yoyokuo