The Silicon Carbide Burn-In Odyssey

Imagine you're trying to pack for a long hike in the mountains. You've got a sturdy backpack filled with all sorts of things—snacks, tools, maps. Now, imagine you don't know if any of those tools will break halfway through your trip. You could either wait until the moment of failure, out on the windy cliffside, or you could test everything beforehand—essentially giving your tools a "burn-in" so that anything faulty fails in the safety of your living room, not at the peak. That's pretty much the conundrum facing the silicon carbide (SiC) industry today, especially in the world of automotive manufacturing. Welcome to the wild terrain of SiC burn-in testing.

The Automotive Industry and SiC Burn-In: Reliability Above All

The concept of "burn-in" is simple but crucial. It involves pre-stressing a component to screen out early failures. In the automotive world, where safety is paramount, there's no margin for error. Burn-in is used extensively here to ensure that electronic parts survive extreme stress before they hit the road. The status quo is that everyone, from ON Semiconductor to Infineon, employs burn-in for automotive silicon carbide parts, because the failure rates without it can be catastrophic. A serious player in the automotive sector simply cannot afford to have a subpar product.

Reducing Burn-In—The Future is Coming (But Not Yet)

Now, here's the interesting bit: while burn-in is still a necessity, there is a clear trend toward reducing its reliance and duration. Everyone wants burn-in to go away. Why? Because it's time-consuming, costly, and frankly, a hassle. Think of it as a high-maintenance insurance policy. Some companies have even tried skipping it—with disastrous results. Fail rates went up, and suddenly they were shipping products that belonged in low-demand markets, not high-stakes environments like automotive.

The industry would love to get to a place where burn-in is unnecessary. However, that future depends on improved gate oxide quality—essentially the insulative "skin" over key components. Better oxide quality means fewer failures without the need for heavy burn-in.

Wafer-Level Burn-In vs. Package-Level Burn-In—Where the Real Game Begins

Traditionally, burn-in was done at the package level—basically, testing individual devices in their final form. Enter Aehr Test Systems, who decided to flip the script. They brought wafer-level burn-in into the mix, meaning burn-in could be performed earlier in the process, saving costs before devices are fully packaged. Imagine finding out that a batch of cookies was inedible before you boxed them all up to sell. That's wafer-level burn-in in a nutshell.

Wafer-level burn-in is definitely catching on, especially in automotive. This trend is partly driven by the demand from savvy automotive customers who want proof of reliability from the get-go. However, wafer-level burn-in isn’t without challenges—wafer size, die configuration, and contact pads all need customization, making it technically more complex than package-level testing.

The Transition to Eight-Inch Wafers—Bigger Wafer, Bigger Savings

Another big wave in SiC is the shift to eight-inch wafers. Here's where things get exciting. Imagine making pizza—a larger pie means more slices without increasing the cost of ingredients by much. By moving to an eight-inch wafer, manufacturers get roughly 80% more die per wafer, but costs don’t go up linearly. While not all processes scale seamlessly, most cost increases are in the 10-20% range, meaning that per-die costs drop significantly. This efficiency is a huge factor for investors watching closely to see if the silicon carbide players can get their price-per-kilowatt low enough to compete with traditional silicon parts.

Trench vs. Planar—Which Path Will Dominate?

If burn-in is like testing your tools before a hike, then trench versus planar MOSFET technology is like debating whether to climb or take a steep trail up the mountain. Trench designs, while trickier to engineer due to complex oxide interfaces, offer a more compact die size and better cost efficiency in the long run. While some companies, like STM, have publicly voiced skepticism about trench designs ever being as stable as planar, the market seems to disagree. Most players are transitioning, including heavyweights like Infineon and ROHM.

This debate impacts Aehr Test Systems too. If more companies move to trench designs, it means testing complexity increases. Trench devices are denser and have different failure modes, which could create more demand for mixed-mode testing—not just gate stress but other stress types too. Aehr, already holding a strong position in wafer-level burn-in, might see more opportunities in this changing landscape.

Burn-In in 20 Years—To Be or Not To Be?

The billion-dollar question remains: will burn-in still be around in 20 years? The short answer is maybe, but it might look very different. Think of burn-in as a dial that keeps getting turned down. Improvements in oxide quality, better testing methods embedded in wafer processing, and improved screening techniques could reduce the need for a dedicated, time-intensive burn-in phase. It could eventually morph into something that's part of the earlier production process, making traditional burn-in obsolete.

However, reaching that point depends on gathering enough data to convince everyone—from car manufacturers like Tesla to the fabs—that skipping burn-in is risk-free. Data speaks louder than anything, and right now, that data says, "Proceed with caution."

Wrapping Up: Silicon Carbide’s Journey Through Complexity

Silicon carbide's path through burn-in, trench technology, and eight-inch wafers is a lot like exploring uncharted territory. You’re balancing on the edge of technical possibility, economic viability, and raw competitive pressure—and every decision impacts the future. For investors, the key lies in understanding which companies are optimizing their burn-in strategies, which are ahead in adopting trench over planar designs, and which are best positioned to capitalize on the cost efficiencies of eight-inch wafers.

The journey may be long and filled with challenges, but it's also one where those who innovate most efficiently will claim the greatest rewards. And that, after all, is what makes this hike so exhilarating.