Aehr comments on Tesla SiC reduction

At the Power America conference on Wide Bandgap Semiconductors held in Raleigh, North Carolina, Aehr Test Systems' CEO Gayn Erickson spoke about Tesla's recent statement about cutting its use of SIC

Erickson commented: “At Tesla’s Investor Day held in Austin, Texas yesterday, Tesla discussed their plans for a next generation drive unit that includes an electric motor with an integrated DC to AC power inverter based on SiC semiconductor MOSFETs. In their presentation, Tesla stated that this new inverter would have a 75 percent reduction in SiC. Aehr wants to make it clear that despite Tesla’s statements yesterday, Aehr does not expect a 75 percent reduction in the total market for SiC wafers."

“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."

“Specifically, Telsa clarified that the 75 percent 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."

"Also, we believe that the new chips in the lower cost models will be 100 Amps per device versus 50 Amps per device today and likely 50 percent 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. Tesla did not provide timing on availability of this new drive unit and platform nor whether it would coincide with a new Giga-factory such as the announced new factory to be built in Mexico, or whether this would or could be made in one of Tesla’s current Giga-factories. Tesla stated that this future platform and drive unit would still be on a 400V battery architecture.

“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 SiC devices which each have two SiC die in each device package. These 48 SiC devices can drive 400A on the 400V system to drive the engine at a simplified 160 kVA power (400V times 400A = 160 kVA).

“The SiC 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 SiC and had a lower current density per unit area. They were also rated at lower current than the typical ~ 100A SiC MOSFETs being used in other SiC modules such as those used in other vehicle manufacturers. 100A SiC 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 SiC materials. Aehr believes it makes sense and stands to reason that Tesla would make a lower cost lower power inverter and drive unit for a new low-cost platform. An inverter made of 12 100A SiC 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 SiC devices is approximately 50 percent 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 percent less than the current 48 die design, the die themselves are estimated to be about 50 percent larger, or require 50 percent more wafers for the same number of die.

“In addition, during the Q&A session, Tesla further clarified that the new inverters would be made from a new Tesla-proprietary custom module package, and that Tesla would purchase the die from multiple manufacturers and package them in this Tesla-proprietary custom module. Again, Aehr sees this as a natural roadmap and consistent with the roadmaps stated by major manufacturers of SiC 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 SiC 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. Therefore, we believe the business use case for our solution actually increases. Wafer level test and burn in of 100 percent of die and extended burn in times will be required to earn Tesla’s business.

“For its fiscal year ending May 31, 2023, Aehr is reiterating its previously provided guidance for total revenue to be $60 million to $70 million, with strong profit margins similar to last fiscal year. Aehr also continues to expect bookings to grow faster than revenues in fiscal 2023 as the ramp in demand for SiC in electric vehicles increases exponentially throughout the decade.”