Biggest Interview – Edoardo MERLI, STMicroelectronics Defines the New-Age of Wide-Bandgap Technology

In this biggest interview of this month, Niloy talks to Edoardo MERLI, EVP & Power Transistor Sub-Group General Manager, ADG from STMicroelectronics. During an official media event, Edorado underscores the company’s strategies in the wide-bandgap technology. He also elaborates on the technical architecture, benefits and future of wide-bandgap devices and not to miss sharing ST’s strategic expansion in this segment with their leading SiC/GaN portfolios. Edited Excerpts Below.

While implementing a solution for a specific application, operating and working capability during the transition becomes crucial. It is said that there is a significant difference between wide-bandgap devices versus conventional silicon technology in which the switching loss is quite different. Hence how ST does plans to maximize the benefit of using a wide-bandgap device in a scenario on how to control the switch on this device. Also, the cost seems to be a crucial factor in which cost for designing and manufacturing wide-bandgap devices, which are still much higher than silicon MOSFETs? Your comments, please.

As far as the first part of the question, the silicon carbide and the wide bandgap technology, for their characteristics, allow to get them into better efficiency and to have improved performances there. As far as how they are controlled, SiC has practised standard gate drivers controlling them at different voltage tensions there. And then this is another important parameter of the technology itself. We are working on it, offering different types of voltage level control depending on the application, and then we at ST are also developing drivers for that.

Then if you are looking at the GaN normally-off HEMT type of solution, the control is a little bit more complicated. But there are drivers also on that. And then also in this case we are developing specific drivers as well. In the case of D-mode, the drivers are more standard. So, of course, the driving capability is coupled together with the main transistors, and then we see this allows overall to reach the level of efficiency that we have commented on in the presentation.

The second part of the question was about the costs. So let’s take the silicon carbide. It is where we are looking at the cost difference between the SiC component itself and comparable silicon technology there. So, the first comment is that it has been already proven in a lot of applications that system-wise use or adoption of SiC devices are leading and allowing to have a decrease in system cost, because of the advantages that the silicon carbide devices are offering in terms of reduction in the cooling system, weight, volumes and whatever. So, this is already a fact.

But as a second point, there are a number of technologies, especially the substrate on the material that we are working on. There are other companies who specialize in the only materials or equipment to handle the materials and substrate that we are working on. We are really already leading towards a significant reduction in terms of cost. So, there will be a reduction in terms of the cost of the device itself, which will be achieved through this improvement in technology.

And then already the silicon carbide allows a reduction in the system cost that makes it viable and actually advantageous to use the silicon carbide instead of the silicon-based type of solutions.

The industrial sector demands a more power-efficient power supply, hence what is ST’s strategic expansion with offerings to advance SiC/GaN portfolios complementing the industrial sector including the bullish renewable market?

So definitely the SiC and GaN are suitable for a number of industrial applications. So today we are seeing SiC already used for high power industrial applications for miniaturization and optimization, also for power supply and then UPS backup systems for data servers and data clouds there.

For energy-specific, we are completing the development of higher voltage families, such as 2.2 kV silicon carbide technology, which is specifically for the energy segment. And then I mean, most of these solutions actually are coming into modules that are widely adopted in standard or industry-standard packages, such as ACEPACK 1 to 2 there.

For GaN, today we see it definitely used in power supplies, mostly or more, at this stage of the market, in power supply for laptops where the integration of low power GaN actually allows to integrate a power supply into laptops themselves. That is definitely a scenario that we are already seeing there, then maybe going ahead.

And then also there we are offering a specific package leveraging the miniaturization and integration capabilities of GaN. Then in the future again, maybe GaN will have higher voltage families, and expand its use into an even wider industrial application.

Given the strategic market of APAC; how ST is focusing on the newer sectors with its WBG offerings?

ST was the first Company to produce automotive-grade SiC MOSFETs and these have been successfully used in the nascent EV industry, which is helping to pave the way for large-scale adoption of them. ST’s undisputed leadership in this field is also attracting a lot of interest from the Automotive Chinese market which is by far the largest in the world. Our presence in Singapore with a dedicated 6” fab for SiC also attests to our efforts to be present in the APAC market. We are also expanding on local competencies to create research collaboration agreements on the new materials. We should not forget that we have already a very strong presence with our backend plant in Shenzhen, and as well, we have strong technical support in the field, which helps customers by facilitating product adoption. With the strength of our local teams, we can say that we have the ambition to be perceived as a local supplier.

How Wide Bandgap Semiconductor can transform the automotive sector and ST’s key focus into this segment?

The transition from internal combustion engines (ICEs) to electric powertrains is an unstoppable trend — many established carmakers have announced plans to discontinue ICE-vehicle production — that can be shaped and accelerated by the adoption of WBG semiconductors because carmakers are always striving to make their models more efficient so that their vehicles can be driven for longer distances with less-frequent recharging. Only WBG semiconductors offer such promise so they are instrumental in driving the transition towards sustainable mobility.

Kindly elaborate on the Design advantages of using SiC MOSFETs?

SiC MOSFETs are used essentially because they can cut losses, which manifests as lower heat dissipation, in power conversion processes. Reduced energy losses, due to both conduction and switching, impact a key parameter, efficiency, enabling significant improvements. These improvements reduce the usage of conventional energy sources like oil or coal, reduce pollution, and extend the large-scale deployment of alternative renewables like solar or wind. EVs enable carmakers to offer models that can be driven for longer distances with less frequent recharging so they will be perceived as a viable alternative to fuel-based powertrains.