Tesla moves to cut SiC use in electric vehicles shakes market
Tesla is developing a new powertrain for lower cost electric vehicles (EVs) that could use 75% less silicon carbide (SiC) power MOSFETs.
The announcement sent shockwaves through the financial markets, prompting some companies to respond with more detailed analysis.
The key point is that the powertrain, expected to be a lower power hybrid SiC-silicon IBGT design in a custom module, will be in lower cost vehicles from 2025 at the earliest. This will drive up the volume of EVs sold as traditional combustion engine vehicles are phased out in 2030. The increase in power will mean larger devices, and the increased volume will also mean more wafers are shipped.
“Tesla has announced that it will use 75% less SiC, a disaster for the SiC industry. This is worrying on first analysis, suggesting a potentially drastic downward revision to SiC’s addressable market,” said analysts at Oddo.
“Tesla’s inverter modules date back to 2017 and each contains 48 [SiC] MOSFETs. The more recent modules on the market contain 12, i.e. 75% fewer… which is precisely the figure mentioned by Tesla. So Tesla may well be using this update to align itself with the market’s most advanced standards, but probably not before 2024 or 2025.
“But this would above all mean that this traditional drive towards miniaturisation and fewer components is already known and incorporated into the ramp-up plans of the main SiC wafer, chip and module manufacturers and equipment makers, and that this announcement merely factors in this development and therefore will not affect the market’s prospects.”
US SiC processing equipment maker Aehr Tes Systems in California was particularly hard hit by the response to the Tesla announcement, while ST Microelectronics, the current SiC supplier to Tesla took less of a hit.
“Aehr wants to make it clear that despite Tesla’s statements yesterday, Aehr does not expect a 75% reduction in the total market for silicon carbide wafers,” said Gayn Erickson, President and CEO of Aehr Test Systems.
“In summary, we believe the announcement by Tesla does not impact the market significantly, either higher or lower, as they are adding a new half power drive train to be used on a new lower cost platform that will increase the market opportunities for Tesla and help drive volumes particularly in lower cost target markets such as China, but also in the US and around the world. The move to larger die to be packaged in module form is seen as a benefit for Aehr’s wafer level test and burn-in solution total available market.”
The company makes test systems for burning-in semiconductor devices in wafer level, discrete die, and package part form, and has installed over 2,500 systems worldwide for the automotive and mobility markets.
“Specifically, Telsa clarified that the 75% reduction applies only to the next generation lower cost drive units to be included in the new model platform, which is still in development with a yet to be announced initial ship date. Tesla clarified that this will not impact the current high-performance model platforms including the Model S/X and Model 3/Y vehicles,” he said.
“Also, we believe that the new chips in the lower cost models will be 100A per device versus 50A per device today and likely 50% or more larger in surface area; therefore, the number of wafers required will be less impacted. This is important as Aehr’s total available market is primarily driven by the number of wafers required, not the number of devices.
“The current Model S/X and Model 3/Y platforms today use an inverter using a half bridge rectifier on each of three phases used to power the engine. Both platforms and both models in each platform all use the same inverter that uses 24 silicon carbide devices which each have two silicon carbide die in each device package. These 48 silicon carbide devices can drive 400A on the 400V system to drive the engine at a simplified 160 kVA power (400V times 400A = 160 kVA).
“The silicon carbide semiconductor for the inverter on the current Models 3, Y, S, and X were originally selected in 2017 and used with the introduction of the Model 3 in 2018. These were earlier generations of silicon carbide and had a lower current density per unit area. They were also rated at lower current than the typical ~ 100A silicon carbide MOSFETs being used in other silicon carbide modules such as those used in other vehicle manufacturers.
“100A silicon carbide MOSFETs are also the “sweet spot” for yield as devices exceeding 100A per device yield have been widely reported to have a drop in yield quickly with higher current due to the defect density of silicon carbide materials.
“An inverter made of 12 100A silicon carbide devices would provide a 200A, 400V, 3 phase 80 kVA inverter and create a lower cost drive unit that would be only half the power of the current drive units in current models.
“In Aehr’s opinion, putting a Model 3 inverter into a lower performance “Model 2” vehicle seems like overkill and unnecessary. It is also important to understand that a 100A device using today’s generation of silicon carbide devices is approximately 50% larger than the devices used in the current Telsa inverters. So, while this new lower performance 800 kVA inverter only uses 12 die or 75% less than the current 48 die design, the die themselves are estimated to be about 50% larger, or require 50% more wafers for the same number of die.
Tesla also plans to use a new proprietary custom module package, buying die from multiple manufacturers. This is positive for suppliers such as STMicroelectronics, Infineon, Wolfspeed and onsemi. ST has been ramping up its module R&D and manufacturing and could well be a supplier for this as well.
“Aehr sees this as a natural roadmap and consistent with the roadmaps stated by major manufacturers of silicon carbide where the electric vehicle inverters will migrate multi-chip modules to reduce power conversion losses, improve thermal performance, simplify design, and lower overall cost of the inverter system.
“As companies migrate to silicon carbide modules with multiple die in a single module package, the need for wafer level test and burn-in become critical to ensuring automotive quality and reliability as well as cost as the yield loss as a result of the stress test induced failures during burn-in become extremely expensive as a single die failure in a module results in throwing away the entire module including the other die in the module.
This is backed up by other analysts who had been pointing out that current SiC devices are too expensive, hence the drive to more capacity such as the wafer plants being built by ST in Catania, onsemi in the Czech Republic and Wolfspeed in the US.
“The share price of whole SiC supply chain has been under pressure following Tesla announcement that its new drive platform will use 75% less SiC. We view this announcement as a new opportunity for the SiC market as it is entering into the low-end BEV market. We talked to both ST and onsemi and see more upside on their revenue growth,” said analysts at Exane.
“We think this solution is paving the way for mass adoption of BEV and is significantly increasing the total addressable market for SiC.”
“While we have limited visibility on Tesla’s SiC strategy going forward, STM has firmly reiterated its short to medium term SiC targets, showing that management seems to have a rather good understanding of the situation and there is limited downside over 2023-25,” said analysts at Kepler. The visibility beyond 2025 when the next drive unit could ramp is more limited, even though nothing is sure at this stage.
“We believe Tesla is also likely to use Soitec’s SmartSiC wafers, which could reduce SiC die size by around 20%,” said analysts at Jeffries. “The timing of the new platform’s introduction is unknown, but we don’t expect suppliers like STM and On Semi to see any negative impact in 2023 or even 2024.
“Tesla’s approach is also likely to be duplicated by other OEMs. Overall we expect strong volume growth in SiC over the next 5 years due to its rising EV penetration, amidst strong underlying EV growth. However, growth beyond 2024 may be somewhat lower than previously expected, while pricing could come under pressure in the event of over capacity.
www.st.com; www.onsemi.com; www.wolfspeed.com; www.infineon.com
