AUTOMOTIVE Is SiC the Key to T
he evolution of electric vehicles (EVs) has necessitated advancements in various technological domains, and Silicon Carbide (SiC) is emerging as a pivotal material in this transformation.
Globally, one of the biggest concerns of existing and potential EV drivers is ‘range anxiety,’ which is partially due to the current energy density of Lithium-based batteries, partially due to access to charging infrastructure, and partially due to the long charging time. However, the combination of three technical elements would solve the range anxiety with ultra-fast charging capability: 800V vehicle architecture, battery cells with more than 3C charging capability, and super high-power DC charging infrastructure.
SiC is essential in two of the three key elements: 800V BEVs and a super high-power DC charger. According to Power SiC report from Yole Group, the global market for SiC in automotive applications is projected to grow significantly. SiC’s ability to operate at higher voltages, temperatures, and frequencies with lower energy losses makes it a critical component in modern EVs. Yole Group deeply analyses the latest manufacturing trends related to SiC technologies in its latest report, Power SiC – Manufacturing.
For the SiC MOSFET itself, there is progress with both planar and trench devices, which will also co-exist in the coming years with an increasing focus on trench devices. Planar SiC devices feature a flat structure
that provides excellent thermal management and lower on-resistance, making them ideal for high-voltage applications within EV powertrains. In recent years, significant advancements have been achieved by scaling down the channel and gate lengths, refining both channel and epitaxial layer doping profiles, reducing the drift layer with a high-quality epitaxial layer, improving metallisation to create low-resistivity ohmic contacts.
On the other hand, trench devices, utilising a vertical structure with trench gates to achieve higher current densities and reduced conduction losses, are particularly beneficial for applications requiring compact designs
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with high power-handling capabilities. Apart from improvements such as higher current density and reduced conduction losses, the vertical gate oxide has been significantly optimised to conquer the concerns on reliability and yield.
Another popular idea is hybrid devices. Hybrid SiC modules combine the benefits of both SiC and silicon devices, offering a balanced approach to performance and cost. These modules are particularly useful in applications requiring high power density and efficiency, such as onboard chargers and inverters in 800V systems. Hybrid modules can bridge the gap between current silicon technology and full SiC adoption, providing a pathway for incremental improvements in EV performance.
Hybridisation can be realised at two different levels: hybrid dies or hybrid discretes. Bare SiC MOSFET and Si IGBT dies can be packaged into one module, or discrete SiC MOSFETs and discrete Si IGBTs can be connected in parallel on boards. Each method needs to carefully control the opening and closing of gates from different dies to get the desired switching performance. Multiple gate-driving solutions are under consideration to get a good balance between performance, cost, and reliability.
The complexity of SiC device fabrication JUNE 2024 | ELECTRONICS FOR ENGINEERS
and the limited availability of SiC substrates can pose supply constraints. However, the growing market incentivises investment in SiC manufacturing capabilities, leading to advancements in production techniques and increased capacity.
Apart from the investments by companies such as Wolfspeed, STMicroelectronics, onsemi, Infineon Technologies, and Rohm, China is also making significant strides in the SiC market, with several emerging players contributing to the global supply chain. Over the past year, some leading SiC substrate players, such as TankeBlue and SICC, have shown the quality of their substrates meets the requirements of international IDMs. The excessive capacity brings an immediate price slashing, which is becoming more intense this year and will likely last for the next few years as the industry moves toward 8-inch wafers.
The contributions of silicon carbide to 800V vehicle architecture and ultra-high-power DC charging infrastructure are instrumental in solving range anxiety and enhancing overall EV performance. As the market for EVs continues to grow, the role of SiC will become increasingly prominent, driving further technological advancements and reshaping the future of electric mobility. Yu Yang, Ph.D., Principal Analyst, Automotive Semiconductors at Yole Group.
Electric Mobility? The market, technology, and supply chain aspects of SiC for EV applications
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