Editor-in-Chief Foreword

In 2020, we jointly experienced the global pandemic of the COVID-19 epidemic. Nearly 2 million people passed away quietly. Respecting life, respecting science, and uniting to fight the epidemic have become international consensuses. The lockdown of Wuhan, raging floods in the Yangtze River, bushfires in Australia, locust scourges in Africa, and the outbreak of fierce wars in the Nagorno-Karabakh region are all vivid in our minds. It can be said that 2020 was a year of great disasters. year; but this is by no means all. In 2020, we also witnessed the signing of RCEP regional free trade cooperation by 15 Asia-Pacific countries, boosting world economic confidence, SpaceX achieving the first commercial manned space flight, and the Chang'e-5 mission achieving a complete success. At a time when the world economy was severely impacted, China became the only major economy to achieve positive growth. As the engine of economic recovery, the semiconductor industry has also dared to take on its responsibilities in 2020 and achieved great results: in the year of 5G, the 5nm 5G chip was strongly launched, and Apple launched the A14 Bionic using TSMC's 5nm process, integrating 11.8 billion transistors. Since then, Huawei and Samsung have also released the Kirin 9000 series and Exyons 1080. The exploration and implementation of EDA on the cloud, EDA software vendors, IC design companies and foundries are cooperating and promoting, can adapt to the needs of EDA tool use, have large-scale automatic intelligent scheduling of computing power, and massive cloud resources to provide elastic computing power support, directly improve the research and development cycle and yield rate of chips, and reduce chip design costs. 3D advanced packaging technology has steadily improved, breaking through the bottleneck of Moore's Law. It has obvious advantages in terms of integration, performance, power consumption, etc. Samsung announced this year that its new X-Cube3D packaging technology is ready for use... Of course, as a rising star in the semiconductor field, third-generation semiconductors and other compound semiconductors have also attracted much attention and have many highlights. Please take a look at the wonderful views of the Belgian semiconductor company Cissoid below!

    "Compound Semiconductor" exclusive interview with Dr. Luo Ningsheng, General Manager of Cissoid China          

Dr. Luo Ningsheng is currently the General Manager of China of Belgian Cissoid Company. Previously, he worked in semiconductor market and business management for a number of European and American semiconductor companies, mainly responsible for China and Asia-Pacific markets and business. These companies include Synaptics (NASDAQ: SYNA) in the United States, Silicon Data in the United States, PicoChip in the United Kingdom, and Innovative Micro Technology in the United States. He received a PhD from the Shanghai Institute of Technical Physics, Chinese Academy of Sciences, and subsequently spent many years as a visiting scholar in Europe and the United States engaged in materials physics research, including solid surface physics research at the Max Planck Institute for Fluid Dynamics in Göttingen, Germany, and semiconductor nanomaterials research at the Department of Physics at the University of Louisville in the United States.

Q 2021 is coming. Facing the new year, how do you view the development and changes of the compound semiconductor industry, and what are your conclusions and insights about 2020? A Following Tesla, in 2020, as BYD took the lead in officially launching electric vehicles driven by SiC MOSFETs in China, major electric vehicle manufacturers are also paying more attention to the application of SiC in electric vehicles. In terms of OBC, DC-DC and charging piles, relatively low-end SiC MOSFETs can generally be used, which can improve efficiency and reduce volume and weight while keeping costs relatively low. For motor drive applications, in order to pursue the highest possible efficiency and lowest heat loss, high-end SiC MOSFETs (that is, the internal resistance is relatively small) tend to be used. In terms of electric vehicle motors, the industry has generally confirmed that the replacement of traditional IGBTs by SiC MOSFETs can increase the energy efficiency of the overall vehicle by 5-10%, which means that it can increase the cruising range by 5-10% under the same battery pack conditions, which is quite attractive. 2021 will be the year when the application of SiC in the field of electric vehicles begins to explode, because this year's large-scale shortage is a sign. In addition, GaN has also developed very well recently, and its main performance is in fast chargers for mobile devices. As it involves consumer electronics applications, its demand will be very large, so GaN shipments will soon surpass SiC devices by orders of magnitude.

Q With the rapid development of 5G, new energy vehicles, big data, AI, IoT and other technical fields, it will bring many opportunities to compound semiconductors. What challenges and opportunities do you think compound semiconductors face?                                                                                                                                                                                         Compound semiconductors (SiC and GaN) being new semiconductor devices that want to replace traditional Si devices, the biggest challenge is cost control, which involves the control of production yield and production scale. Only by continuously improving the yield rate and expanding the production scale can the cost be gradually reduced, thereby winning wide application in the market. Challenges are also opportunities, and this is also the commanding heights for various compound semiconductor manufacturers to win and gain market share.

Q Silicon carbide (SiC) is a material with great development prospects, especially in the application of power electronics and microwave radio frequency devices. It is currently receiving great attention. How does your company view the market development of silicon carbide? How to promote the upgrading and development of silicon carbide materials? A

As third-generation semiconductors such as SiC power semiconductor devices become more mature and popular, they will simply replace Si devices in applications in the early stage. However, in the later stage, they will actively take advantage of their performance advantages to create many new applications, that is, they will get involved in applications that were previously inaccessible to Si devices. For example, the inherent high-temperature resistance of SiC is a very good match with Cissoid high-temperature semiconductor devices, which will greatly change the pattern of power system design and provide design engineers with new and broad room for expansion. These typical, future high-temperature, high-power-density applications include deeply integrated electric vehicle powertrains, multi-electric and all-electric aircraft and even electric aircraft, mobile energy storage charging stations and power banks, and various power applications where liquid cooling is severely limited. 

The powertrain of electric vehicles (motor, electronic control and gearbox) has moved towards three-in-one, but currently it is only structurally stacked together, which is weak integration. Structurally speaking, in the future, deep integration of the powertrain is an inevitable path, because this may reduce the volume by about one-third, the weight by about one-third, and the internal consumption by about one-third, and may reduce the total cost by 2 to 4 times. However, the electronic control part will be closely integrated with the motor, and deep integration will greatly increase the power density. High temperature is the biggest challenge that cannot be avoided.

In traditional aircraft, the mechanical actions that control the tail rudder, wings, landing gear, etc. rely on classic hydraulic transmission. As a liquid, hydraulic oil is greatly affected by the environment and has high maintenance costs. Currently, there is a trend towards partial or complete electrification, which is the concept of multi-electric and all-electric aircraft. Using electric motors instead of hydraulic oil circuits on the aircraft to achieve mechanical operation has high reliability, strong maintainability, and facilitates redundant backup design. However, the biggest dilemma is that the motors and electronic controls on the aircraft are not allowed to be equipped with water cooling, and can only rely on forced air cooling and natural cooling. Therefore, to realize the electronic control design of multi-electric or all-electric aircraft, or even electric aircraft, the major technical problem that needs to be solved first is high temperature. 

In addition, there are many application scenarios, especially with the large-scale popularization of electric vehicles, semi-mobile energy storage charging stations and fully mobile power banks will effectively fill the gaps in fixed charging in certain scenarios. However, for this type of mobile charging application, the water-cooling mechanism will not only bring the burden of extra weight and volume, but more importantly, it consumes the stored electrical energy it carries. Therefore, natural cooling will be the best way for the electronic control, but the thermal management problem of the electronic control system must be properly handled.

In addition to the above three typical high-temperature applications, in many special industrial applications where liquid cooling is severely limited, electronic control systems will face the same high-temperature challenges. High-temperature electrical control technology is the key to realizing the above high-temperature applications. Its core implementation technology is the high-temperature packaging technology of SiC power devices and the matching high-temperature drive circuit technology.

SiC materials and their device structures have inherent high temperature resistance, and can even withstand temperatures of 400 to 600°C under vacuum conditions. In practical applications, in order to prevent oxidation caused by exposure to air, SiC devices must be packaged, and if they want to withstand high temperatures, they must use high-temperature resistant packages. The junction temperature of 150°C is currently the highest standard in the industry. The 175°C junction temperature level has just begun to be revealed. There are quasi-standardized packages that can be used. Packages with temperatures of 200°C or higher have very strict requirements on packaging materials and processes, and must be customized according to the characteristics of the bare chip to ensure thermal conductivity and heat dissipation performance requirements.

The application of SiC power devices and modules is inseparable from driver circuits and their corresponding chips. However, most driver circuit chips are ordinary silicon devices and cannot withstand high temperatures. If they can work at high temperatures such as 175°C for 1,000 hours, it is already rare. In addition, high temperature resistance is only one aspect of the problem. What is more serious is the consistency of device performance at high temperatures. The performance of ordinary silicon devices weakens very quickly above 70°C, so they cannot be used at high temperatures. After more than 20 years of innovative R&D and application testing, Cissoid's SOI special silicon devices have reached a high temperature resistance of 175°C and can operate continuously for 15 years. The performance has excellent consistency across the entire temperature range and is a pillar supporting SiC high-temperature applications.

Q: Please share your views on how China’s compound semiconductor industry should learn from international experience and accelerate industrial development. A Although China started late in the field of compound semiconductors and lags behind foreign countries, this field is very suitable for achieving rapid development in China. There are three main reasons. First, the processes of compound semiconductors are basically at the micron level. From materials to equipment, there is a full set of domestic industrial chain support, and they will not be severely restricted by the need to import fine nanoscale manufacturing equipment (especially photolithography machines). Second, the device structure of compound semiconductors is relatively simple and does not require very complex top-level EDA support. It also eliminates the serious restrictions caused by the need for imports. Third, China has a vast and huge application market. Therefore, it can be concluded that compound semiconductors will be one of the important breakthroughs for the improvement of China's overall semiconductor industry. In recent years, the country has attached great importance to the semiconductor manufacturing industry and has invested a lot. Dozens of wafer fabs have been started, expanded or built. Especially recently, some people in the industry have called for microelectronic system processing to be treated as a separate discipline. This is an excellent phenomenon. However, looking at domestic wafer fabs, they all have new factories and new equipment, and the investment is very large. What is most lacking is talent in the field of process development, and a system for talent accumulation in the maintenance process. Traditional mechanical processing, such as lathes, millers and welders, has a multi-level craftsman system linked to benefits and subsidies to promote and maintain the development of the profession. Such an important microelectronic system processing industry should have a more comprehensive talent training system.