The mass phase-out of the internal combustion engine (ICE) vehicles is rapidly approaching. As of October 2022, 51 countries are planning to restrict or ban the sale of ICE vehicles by 2050 at the latest. With light-duty private vehicles being targeted first and foremost, the electric vehicle (EV) industry is naturally readying for a huge spike in demand. However, while EVs offer some advantages like zero emissions, lower maintenance, and higher energy efficiency, the industry is still facing a few major challenges. Mainly the limited range, the higher initial cost per vehicle and the longer charging times compared to traditional “fueling” are of concern.
Some of those difficulties could be solved via the improvement of the microelectronic components’ materials; for example, using compound semiconductors (CS), which are made of two elements, over the standard, mono-element, silicon. One of those CS is silicon carbide, otherwise called by its chemical formula “SiC”, which has attracted increasing attention in the semiconductor sector due to its promising properties.
What is SiC ?
Silicon Carbide – a hard, semiconductive material comprised of carbon and silicon atoms neatly arranged into one of 250 existing polymorph crystalline structures of the compound. More commonly referred to as SiC, this incredible compound of cosmic origins was first discovered under its mineral form by French chemist Dr. Ferdinand Henri Moissan, in 1893, while he was examining rock samples from Canyon Diablo crater in Arizona. From these humble Franco-American origins, the compound rose in popularity initially as an industrial-strength abrasive, thanks to its low cost and Mohs level of 9, making it one of the hardest materials in the universe. From there its influence spread to other sectors such as automobile, electric and nuclear industries. Nowadays, SiC is emerging as a disruptive competitor to silicon in the semiconductor industry.
Why use Silicon Carbide ?
Compared to its older cousin, silicon carbide offers a range of interesting properties. The combination of SiC’s thermal conductivity and wide bandgap, means that components made with it are smaller and suffer less from heat-related efficiency losses. These reasons make it ideal for power electronics, which are responsible for the controlling and processing of electricity within a machine. In EVs, silicon carbide is thus present in the converter, inverter, and on-board charger, all of which make up the drive train of the car, allowing for higher efficiency and smaller sized batteries. Smaller batteries mean fewer resources used for the production, which considering the current ecological and geopolitical situation, allows for both a lower total carbon footprint, higher market security and a decreased EV price.
The Challenges
Regardless of silicon carbide’s promising properties, the technology comes with few caveats; mainly the production of SiC based components has proven itself difficult because of the costly and long manufacturing process of the material, the technological challenges, and the particularly high-quality standards of the microelectronics. A way of bringing the production costs down would be increasing the diameter of the wafer, the thin semiconductor (here SiC) disc upon which the electrical circuits can be printed, as an increase of the wafer diameter directly translates to the number of microelectronic components produced. This approach has been adopted within the industry with very slow success for the past 20 years, during which SiC wafer size has seen an eightfold increase from 25 mm to 200 mm wafers, however nowadays, the Physical Vapor Transport (PVT) technology, which is the currently used manufacturing process for SiC, seems to be reaching its limits. For that reason, the pioneers in the sector are searching for other manufacturing processes for SiC substrates like High Temperature Chemical Vapor Deposition (HT-CVD) or Liquid Phase Growth. Another source of innovation in the SiC industry are engineered materials, such as Soitec’s SmartSiCTM, which consists of bonding a very thin layer of high quality SiC to a very low resistivity polySiC wafer. According to them, this helps them turn one SiC wafer into 10 plus SmartSiCTM wafers.
Conclusion
Silicon carbide is a wide bandgap semiconductor which has the potential of revolutionizing the power electronics sector, thus contributing to a huge increase in EV efficiency. However, SiC’s high thermal and chemical stability, as well as its tendency to produce defects during crystal growth, render its bulk production costly and its commercialization challenging. To overcome those issues, the industry is searching for ways to increase the yield of SiC substrates manufacturing processes, via innovative technologies such as Grenoble-based Soitec’s SmartSiCTM. Given they succeed, the future of silicon carbide-based power electronics is bright, but to make that happen they need motivated engineers and materials specialist working on advancing the technology in the sector.
Sources
[1] Power electronics in the context of electric plug-in and hybrid vehicles, by Office of ENERGY EFFICIENCY & RENEWABLE ENERGY (USA) ; https://www.energy.gov/eere/vehicles/power-electronics-research-and-development
[2] State-of-the-art of PEC configurations in electric vehicle technologies, by Pandav Kiran Maroti et al. https://www.sciencedirect.com/science/article/pii/S2772370421000018
[3] Power Electronics Technology that supports Smart Grids, by Shinsuke Nii et Masaki Kato https://www.fujielectric.com/company/tech/pdf/57-04/FER-57-4-140-2011.pdf
[4] Soitec on track to enlarge Silicon Carbide product portfolio with first 200mm SmartSiC™ engineered substrate, https://www.soitec.com/en/press-releases/soitec-on-track-to-enlarge-silicon-carbide-product-portfolio-with-first-200mm-smartsic--engineered-substrate?__geom=%E2%9C%AA
[5] SiC based microelectronics’ advantages: https://www.sglcarbon.com/en/newsroom/stories/why-silicon-carbide-semiconductors-have-a-bright-future/
[6] Bulk Growth of Large Area SiC Crystals, by Adrian R. Powell et al. https://www.researchgate.net/publication/303506822_Bulk_Growth_of_Large_Area_SiC_Crystals
[7] Soitec aims for big EV win with Smart Cut SiC wafers, by Adele Hars for the OJO – YOSHIDA REPORT https://www.i-micronews.com/soitec-aims-for-big-ev-win-with-smart-cut-sic-wafers/
