“With the continuous upgrading of the global energy structure, wide-bandgap semiconductor devices have attracted much attention in the industry due to their advantageous characteristics. ST has invested in the silicon carbide field for more than 25 years, and has won more than 50% of the global SiC MOSFET market share; it has also actively carried out technology research and development and capital investment in the field of gallium nitride to accelerate the GaN strategy. Recently, ST held an online media communication meeting on wide-bandgap semiconductors. Edoardo Merli, executive vice president of STMicroelectronics Automotive and Discrete Products Division (ADG), and general manager of power transistor division, focused on the technical advantages and strategic layout of wide-bandgap semiconductors. Great sharing.

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✦ This article is reproduced from: 21ic
✦ Author: Liu Yanxuan

ST has won more than 50% of the global SiC MOSFET market share; and has carried out substrate technology acquisition and production capacity investment in the field of wide-bandgap semiconductors, and has control over the entire production chain. This article shares the reasons for ST’s success in the SiC field, its future strategic plan on how to rank in the forefront of the market, and an interpretation of the prospects for the entire wide-bandgap device industry.

With the continuous upgrading of the global energy structure, wide-bandgap semiconductor devices have attracted much attention in the industry due to their advantageous characteristics. ST has invested in the silicon carbide field for more than 25 years, and has won more than 50% of the global SiC MOSFET market share; it has also actively carried out technology research and development and capital investment in the field of gallium nitride to accelerate the GaN strategy. Recently, ST held an online media communication meeting on wide-bandgap semiconductors. Edoardo Merli, executive vice president of STMicroelectronics Automotive and Discrete Products Division (ADG), and general manager of power transistor division, focused on the technical advantages and strategic layout of wide-bandgap semiconductors. Great sharing.

▲ Edoardo Merli, Executive Vice President, Automotive and Discrete Products Group (ADG), STMicroelectronics, General Manager, Power Transistor Division

Advantages and Current Limitations of Wide Bandgap Devices

According to the IEA (International Energy Agency), the demand for electricity consumption continues to grow, and the global electricity demand growth rate will exceed 30% from 2020 to 2030. On the other hand, subject to the heavy pressure of global environmental degradation, the global agreed carbon emissions need to be greatly reduced, and the power generation ratio of renewable energy needs to continue to increase.

Judging from the proportion of electricity consumption in 2019, industry is the largest electricity consumer. A 1% increase in the efficiency of global industrial electricity use can save the power generation of about 15 nuclear power plants. From electric energy generation, to electric energy transmission, storage and final use, how to improve energy utilization efficiency and increase the utilization rate of renewable energy from the entire power conversion chain is a hot topic of concern in the entire industry. And wide-bandgap devices such as SiC and GaN have better performance than traditional silicon devices because of their natural characteristics.

Compared to traditional silicon-based devices, GaN and SiC can outperform in terms of energy efficiency due to their higher operating voltages, faster switching speeds, and lower on-resistance. Although both are wide-bandgap devices, the device characteristics of GaN and SiC are also significantly different. The operating voltage of SiC is much higher than that of GaN, so it is more suitable for high-voltage applications, such as high-power systems such as automobiles and industries. The switching frequency of GaN is faster, so it is more suitable for applications such as fast charging and RF switches, such as some miniaturized power adapters, RF switches, etc. With wide bandgap devices such as SiC and GaN, simpler and more efficient designs can be achieved over traditional topologies, resulting in overall cost reduction at the system level, miniaturization and weight reduction.

Thanks to these advantages of wide-bandgap semiconductors, it can help the industry to achieve higher energy efficiency upgrades in the fields of industry, consumption, and electric vehicles. Among them, electric vehicles, as one of the important application fields of energy structure upgrading, have made commitments to transformation in all countries and regions. Benefiting from the paradigm shift in the entire automotive industry, the demand for silicon carbide devices will continue to expand.

Taking the inverter of an electric vehicle as an example, the SiC MOSFET inverter can achieve higher integration and smaller volume than the IGBT inverter, and reduce the switching loss by 80%. According to Edoardo Merli, the overall energy efficiency of electric vehicles using SiC MOSFET inverters is much better than that of IGBT inverters under full workload conditions. Moreover, in the actual use of automobiles, more than 95% of the working conditions are under low load conditions. Under such low load conditions, the energy efficiency ratio of the IGBT inverter and the SiC MOSFET inverter differs by 3 to 4 percentage points.

Although wide-bandgap devices have advantages over traditional silicon materials, there is still a big gap between them and very mature silicon processes in terms of production yield, cost, system integration, and reliability.

Silicon carbide has been commercialized on a large scale, but it requires more stringent production conditions than silicon materials, requiring higher temperatures, newer processes and other processing conditions. Silicon carbide still lags behind silicon in terms of throughput and processes. How to realize the iterative upgrade of the process and improve the production yield and reliability are the key issues to be solved by SiC devices. The lack of reliability of GaN is a limitation in its entry into industrial and automotive fields. In addition, achieving higher switching frequencies under higher voltage operating conditions still requires the industry to explore.

In addition, in terms of design, the driving characteristics of wide-bandgap devices are different from those of traditional silicon devices. When developers integrate new materials and devices, it is not easy to directly replace the devices, and the entire driving circuit needs to be improved accordingly. , to achieve a good match between the drive circuit and the main transistor, in order to achieve the best energy efficiency performance. Therefore, many wide-bandgap device manufacturers usually also launch supporting driver devices or co-packaged modules to facilitate system integration for developers. But overall, replacement in traditional silicon device applications still requires some additional work from developers.

In general, as a new material device, improving reliability, reducing costs, and enabling developers to achieve more convenient designs still require the industry’s efforts, and the development of wide-bandgap devices is still on the way.

ST’s SiC and GaN product layout

ST’s investment in wide-bandgap devices has a long history. ST has been deeply involved in the SiC field for more than 25 years. Currently, it has more than 50% of the SiC MOSFET market share, and even 60% in the automotive field. It is expected to reach an annual profit of US$1 billion by 2024.

In terms of product iterations, ST’s SiC devices have achieved mass production and shipment of first-, second- and third-generation SiC products; the fourth-generation SiC products are also expected to pass the certification test at the end of this year and will be launched to the market next year. As shown in the figure below, Rds(on) x Area and Rds(on) x Qg are important performance parameters for SiC devices, and ST’s SiC devices achieve about 20-25% improvement in each iteration process, thereby achieving performance improvement and cost reduction.

To provide customers with a wide range of product portfolios and to facilitate customers to choose more suitable product solutions is the product strategy that ST has always adhered to. In terms of SiC product layout, ST is also launching products of different package types, including both discrete packaged devices and multi-die packaged modular products, such as ACEPACK1-2 and ACEPACK DRIVE, through platform-based Module packaging to simplify the user’s design challenges.

In terms of GaN power product planning, ST has two product portfolios, PowerGaN and MasterGaN. PowerGaN is mainly a discrete GaN transistor, while MasterGaN is a system-level package consisting of drivers and transistors. In addition to the above two power product portfolios, ST is also planning GaN PAs for mobile base stations.

According to Edoardo Merli, ST will continue to promote G-FET, G-DRIVE and G-HEMT products with input voltages starting from 650V in the PowerGaN roadmap, adding 100V products to the existing G-HEMT products. The gallium nitride product portfolio will also be further expanded, adding transistor products with different on-resistance, and will continue to promote the MasterGaN system-in-package. Like SiC products, GaN products are also available in a wide range of packaging forms, such as discrete packages such as QFN, and ST LISI, a new package that can integrate batteries. In addition, ST will continue to study embedded die packaging technology to further improve the integration of packaging. RF GaN products are also expected to be launched by the end of this year.

Sustained winning strategy: full control of the complete manufacturing chain

Maintaining and expanding its 50% share in the SiC market and continuing to expand the market share of GaN products will be an important direction for ST in wide-bandgap semiconductors. In this regard, ST has formulated strategies from upstream and downstream, and carried out two-wheel drive: continuous investment in manufacturing to achieve overall control capabilities; close application-side cooperation with clients to jointly define products. A large amount of feedback information obtained by the client is fed back to the product design, production and manufacturing links for iterative upgrades.

“In addition to technology research and development, we are also developing a strategy for a complete manufacturing chain. The focus of this strategy is to make ST truly have the manufacturing strength of power semiconductor technology.” Edoardo Merli said, “We are investing heavily in expanding the production capacity of SiC and GaN. , ST is very optimistic about these two technologies, so the silicon carbide and gallium nitride power technologies are written into the company’s overall development strategy for the next ten years.”

The complete manufacturing chain strategy includes the realization of controllable strength in the entire manufacturing chain from the previous substrate processing lane to the final packaging test, so as to achieve capacity expansion. Silicon carbide substrates are an important part of the manufacturing chain itself and have a large impact on the cost, yield and quality of chips. The acquisition of Sweden’s Norstel AB (renamed ST SiC AB) gives ST access to the leading silicon carbide substrate manufacturing technology and integrates this technology into its own manufacturing chain. In the future, some of the substrates for ST’s silicon carbide products will be provided by the factory, and some will be purchased from third parties.

According to Edoardo Merli, the first batch of ingots and 8-inch wafer prototypes have been fabricated at the facility, and a wafer utilization characterization analysis is currently underway to allow the prototype wafers to go through the entire process in order to develop the complete process technology. The 8-inch wafer is expected to Mass production will be achieved by the end of 2024. The ST SiC AB factory in Sweden will be built into a comprehensive factory, which will not only undertake the task of substrate growth in the future, but also undertake other subsequent processes from epitaxy to diffusion, and may even provide wafer testing. ST’s two main manufacturing bases in Catania, Italy and Singapore are also expanding their production scale, transforming and upgrading from a 6-inch production line to an 8-inch production line. The packaging and testing of the back-end is mainly completed in two factories in Shenzhen and Bouscula, Morocco, and the production capacity of the back-end will also be doubled.

In terms of GaN, a similar capacity investment and development strategy is also adopted. ST is cooperating with TSMC to release many internal test products to the market in advance and better reach the market through TSMC’s channels. The ultimate goal is to improve ST’s internal testing technology and ultimately serve its clear and definite product strategy. ST’s promotion of Power GaN technology is already on the way, and various products from 100V to 650V will be released one after another, and these will also be born on the 8-inch production line. In addition, ST Catania also has a silicon-based GaN production line for the production of gallium nitride PA products, which is a layout for 5G and 6G infrastructure.

In addition to the above-mentioned complete manufacturing chain strategy, another important strategy of ST is on the client side: a large number of products are equipped to provide valuable feedback information; close cooperation with leading customers is to carry out a new generation of product definition exploration first.

With over 50% market share, ST can get a lot of product application feedback, which is also an important moat that differentiates it from other manufacturers. More than one million vehicles today use powertrains based on ST’s silicon carbide solutions. This is an invaluable source of information for ST to overcome the aforementioned challenges and find many ways to overcome technical difficulties. Very valuable information. Edoardo Merli said that the higher the adoption rate of the product, the more feedback information will be collected, and the more you can understand the performance of the product in specific applications, so that ST can improve product performance, quality and reliability in the future, and you can also use this information. Define the characteristics of new products to meet the needs of different applications.

Close cooperation with leading customers enables product definition to achieve market-leading exploration. Taking the strategic cooperation with Renault as an example, ST works closely with OEMs to develop solutions that meet market prospects, and then OEMs can hand over the solutions to EMS or Tier 1 suppliers for mass production. This collaboration allows ST to truly define technology, and to achieve product definition in the best possible way. This way of working closely with chip manufacturers has gradually become an important trend in the new automotive industry landscape.

Summarize

ST’s strategy on SiC has been completed. With its complete production chain control and leading market share, it will enter a period of rapid development under the rhythm of two-wheel drive. Products on Power GaN will also benefit from the investment in 8-inch production lines, and the exploration on GaN PA will also be a very interesting product direction.