Silicon carbide (Sic) wafers are forecast to continue to grow strongly through 2023, despite a general slowdown in the global economy and other semiconductor material markets. The 2022 Sic N-type wafer output market will increase by about 15% compared to 2021, totaling 884k wafers (150mm equivalent)
The high demand for SiC wafers is due to Si-based power devices approaching their physical limits, especially for high-speed or high-power applications. Sic has more advantages in terms of material characteristics and supply chain maturity. Additionally, demand for electric vehicles, charging infrastructure, green energy production, and more efficient power devices in general drives higher demand for SiCs
While SiC is gaining popularity, its chemical properties make it difficult to process boules into actual wafers, making SiC wafers in short supply. In the past few years, in order to increase the supply of ingots, many companies have announced or started a major expansion of Sic ingot growth capacity, but few companies have actually entered the wafer service market
Part of the gap is being filled by vertically integrated SiC device companies such as Wolfspeed, ON Semiconductor, and STMicroelectronics, which are able to balance their production capabilities internally. Companies like X-trinsic and Halo Industries are trying to bridge the gap by offering process services
The development of Sic is relatively slow. Since the release of the first batch of wafers in 1991, the first full Sic commercial MOSFET has only been launched 20 years later. Ultimately, it was Tesla and its 400V inverters that brought this conforming material to the forefront in 2018. Afterwards, there is growing interest in SiC-based products with high power density, efficiency and high-temperature performance, and the automotive segment is looking for a solution to meet the requirements of under-the-hood applications
For the same reasons as automotive, silicon carbide has started to find its place in the energy sector and may find its way into high-power industrial applications within the next decade. However, with Tesla announcing the reduction of SiC in its future powertrain, both market value and technology may change depending on OEM choices
According to yole's prediction, the global SiC device production capacity will triple by 2027, and the top five companies are: STMicroelectronics, Infineon, Wolfspeed, onsemi and ROHM. Analysts predict that the SiC device market will be worth $6 billion in the next five years and could reach $10 billion by early 2023
To analyze currently available device design technologies, the company compared 1200V transistors with as many as 14 cross-sections. Most manufacturers use planar technology (onsemi, Wolfspeed, Microsemi...), only ROHM Semiconductor and Infineon have chosen trench MOSFETs with more complex designs. ST Microelectronics and Mitsubishi are also betting on trench technology, but so far it has not worked out
By switching from a planar (2nd generation) process to a trench process (3rd generation), ROHM reduced FoM (figure of merit, Rdson*Qg) and pitch size by 50% in just four years. These have been further improved using next-generation, more advanced trench processes.
Wolfspeed prefers a planar design using a diffused MOS process, which reduces die size and FoM by 50% between the first and third generations. By comparing the latest generation of transistors from these two companies, mainly the reduction in pitch size, ROHM's trench version is more advanced in this regard
However, such trench MOSFETs are more complex and require higher manufacturing costs. And this design is more difficult to control the gate oxide thickness, so the weak area in the gate trench can challenge component reliability
While numbers and emerging M&A activity tend to indicate growing interest in this composite material, its expected position in power electronics will only be determined if solutions to the three main barriers currently preventing wider adoption of SiC are found
1. Cost
So far, the cost of SiC modules has not provided the possibility to popularize this technology in electric vehicles other than high-end. For the same reason, the industrial sector, targeting 3300V for its high-power applications, remains hesitant to venture into SiC and relies on the Si IGBT option. According to the analysis, the cost of the substrate fabrication and epitaxy stages accounts for 59% of the total wafer cost (the average cost of 1200V Sic MOSFET), followed by the yield loss of the front-end process (24%).
Wolfspeed and ROHM Semiconductor performed well at the die-ampere cost level, which shows that controlling the entire supply chain has an advantage in the competition.
2. Reliability
Despite integration into commercialized automotive systems (Tesla and Lucid Air inverters/Toyota Mirai II boost converters), there is not enough evidence for long-term reliability of SiC products, which is another reason for the wait-and-see attitude of the industrial sector. a reason
3. Packaging
To fully benefit from the advantages of SiC technology, a suitable packaging solution must be found. But that’s exactly the problem: While there are multiple proven options in the case of SI IGBTs, packaging options for SiC MOSFETs are still in their infancy and showcase only a handful of designs developed by Denso, Wolfspeed and ST Microelectronics. These designs include high temperature compatibility and low loss materials, whether on the substrate (materials with good thermal properties such as AIN and AMB - Si3N4), packaging (high temperature epoxy or silicone gel), die attach (such as silver sintering) or Interconnects (with low inductance interconnects, such as top Cu leadframes). Much work remains to be done before a standardized solution can be provided
Wolfspeed's substantial expansion of production brings new variables
On February 1, Wolfspeed and ZF Friedrichshafen AG announced a strategic partnership targeting future silicon carbide semiconductor systems and devices for mobile, industrial and energy applications. One way to achieve this is to establish significant Sic production capacity in Europe
Wolfspeed's new factory in Germany will be the largest 8-inch dedicated SiC device factory and the only one in Europe capable of volume production of 8-inch SiC wafers (excluding some SiC compatible capacity of STMicroelectronics). This will solidify Wolfspeed's leadership in SiC wafers while also targeting the SiC device market currently dominated by European companies
Through its existing fab in New York, USA, Wolfspeed is currently the only company that can mass produce 8-inch SiC wafers. This advantage will last for two to three years until more companies start to reduce production capacity - the earliest is STMicroelectronics, which will open an 8-inch SiC factory in Italy in 2024-5
Wolfspeed differs from other companies dealing with Sic in that it only focuses on that material. Well-known companies in the power electronics industry - Infineon, Onsemi and STMicroelectronics also have successful businesses in the silicon and gallium nitride markets. This factor also affects the comparative strategy of Wolfspeed and other major SiC players
Analyst firms believe that the automotive industry will account for 70% to 80% of the SiC device market by 2023. With the increase in production capacity, Sic devices will be more easily used in industrial applications such as electric vehicle chargers and power supplies, as well as green energy fields such as photovoltaics and wind energy. However, automotive will remain the main driver and its market share will not change for the next 10 years. This is especially true as regions introduce electric vehicle targets to meet current and near future climate goals
Other materials such as silicon IGBTs and GaN-on-silicon may also become an option for OEMs in the automotive market. Companies such as Infineon Technologies and STMicroelectonics are exploring these substrates, especially because they are cost-competitive and do not require specialized fabs
Wolfspeed's entry into Europe with 8-inch production capacity will undoubtedly target the SiC device market currently dominated by Europe. But it will be interesting to see how the market evolves in the coming years as different strategies play out
