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APEC Insight: GaN Applications & Manufacturing

March 17, 2018

Last week at APEC, I spoke during the industry session (IS11) titled, “Applications and Manufacturing of Wide-bandgap Semiconductors.” First of all, a ton of appreciation for Session Chair Jim LeMunyon (from PowerAmerica) and the APEC committee for including Transphorm’s GaN presentation in this session, along with other excellent talks by folks from Automotive, SiC, and Defense/Infrastructure companies.

I framed my remarks with the facts that Transphorm’s 650 V GaN FETs are—today—in applications ranging from consumer-focused gaming PCs to industrial-focused server power supplies and servo drives. And, that our customer adoption is driven by Transphorm’s constant innovations geared towards high quality and reliability of our high-voltage GaN platform and associated resources.

For those of you unable to attend, what follows is a brief overview of three key points made during that discussion. These points are important to understanding how HV GaN (650V and also 900V) will gain greater traction, as well as what application developers should look for when vetting GaN platforms. Further, they are based on our own experiences that have led to (and will continue to do so) successful customer partnerships that put HV GaN products into the market. Which, in turn, will give the industry as a whole necessary real-world data on GaN’s performance and reliability capabilities. While important for any industry, this is doubly important for a young industry such as ours as we continue to earn customer confidence.

First, Transphorm is one of the few GaN manufacturers that are vertically integrated, with control of materials, device design and wafer-fab, packaging and application engineering. Our foundry is a partnership with Fujitsu Semiconductors and runs GaN on Silicon side-by-side with Silicon CMOS products supplied to automotive customers from the same fab. Disciplined manufacturing in this fab has led to defect densities (measure of yield) for Transphorm GaN FETs reaching the same range as those of Silicon products, giving similar yields as that of Silicon CMOS wafers.

Second, we have established a complete and necessary spectrum of quality, reliability and robustness testing. That spectrum includes:

  • JEDEC and AEC (Automotive) qualifications: Customers of GaN should throw away the largely academic argument that JEDEC or AEC do not apply to GaN. The right question to ask is: “If your parts do not pass JEDEC or AEC today, what is wrong with the platform?” However, as the standard JEDEC and AEC tests are historically applied to Silicon—they may or may not be sufficient on their own for GaN. Considering, we expand our scope of testing to include…
  • Robustness testing: We increase the level of stress for key parameters 5x or more;
  • Application-specific testing: We perform testing reflective of application conditions such as inductive switching stability, life and long-term operation;
  • And, extended lifetime testing: We analyze intrinsic lifetimes with understanding of failure modes, acceleration factors, and activation energies documented.

Third, we are all in power electronics and that means using the power switching devices invariably involves getting the power (heat) out of the package (and the eventually the system). Thermally and mechanically robust packages such as the TO247/TO220s or their surface mount equivalents such as the D2/D3 PAKs or the relatively newer TOLLs are essential to realizing power levels beyond 1 kW. Thinner surface mounts or fancier embedded packages simply do not deliver the higher power and, further, require more complex thermal management. Also, whether such thinner/fancier packages will be able to pass the high standards of Automotive or Industrial qualifications remains a question mark.  As I like to say figuratively, “The Power is in the Package.” (Literally, it means the heat has to get out of the Package, effectively!)

Lastly—and, perhaps the most important of all—public access to quality, reliability, and robustness data is essential. We publish ours so that all GaN manufacturers (and system developers alike) can review the extensive testing we do and adopt similar stringent testing philosophies. In fact, we are sharing this knowledge with the committees such as JEDEC as active leaders in these committees responsible for establishing industry-wide wide bandgap semiconductor qualification and datasheet standards. However, there should be no doubt that already most of these standards are now in place by companies such as Transphorm for high voltage (600 V/higher) as well as EPC and others for low voltage (200 V/lower)

The bottom line is this: the growth of the 650 V GaN market along with the ability to leverage GaN in end products hinges on the quality and reliability of the platform itself. At Transphorm, we have the comprehensive manufacturing control, and testing foundation that sets today’s standard of high performance, high reliability GaN. We’ll continue to enable the wider semiconductor community by sharing our testing methods and results. And, will always welcome any additional testing required by customers or end applications as they arise.

Primit Parikh, Ph.D.
COO & Co-Founder

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