Moore's Law is approaching the limits of physics. "Can't roll" to change the track, wide bandgap semiconductors have become one of the "strange paths" for semiconductor development in the post-Moore era, and in this field, domestic companies are expected to achieve corner overtaking.
Wide bandgap semiconductors refer to semiconductor materials with bandgap widths of 2.3eV and above, represented by silicon carbide (SiC) and gallium nitride (GaN), also known as "third-generation semiconductors". Semiconductor devices prepared from SiC and GaN materials can not only operate stably at higher temperatures, but also apply to high-voltage and high-frequency scenarios, but also obtain higher operating capacity with less power consumption.
Luo Weiwei, chairman of GaN on Si power device company Innosec, recently said at the 2022 ISES China Summit that wide bandgap semiconductors are not advanced processes, and the dependence on equipment will be smaller, and many of the equipment involved can basically be obtained in China, and the core equipment can also be independently controlled in the later stage. "It's a new track and we have a chance to break through."
Wide bandgap semiconductors: an important area for lane change and overtaking
The potential of silicon (Si) materials has been gradually exhausted. Compared to silicon, SiC has 10 times the breakdown electric field strength, 3 times the band gap, 2 times the ultimate operating temperature, and more than 2 times the saturation electron drift rate. SiC also has 3 times the thermal conductivity, which means 3 times the cooling capacity of Si. GaN, on the other hand, has a wider band gap, breakdown electric field strength, and saturated electron drift rate than SiC.
At present, Si is still the mainstream of semiconductor materials, accounting for 95%. Yole predicts that the penetration rate of third-generation semiconductors will increase year by year, with SiC penetration expected to reach 3.75% in 2023 and GaN penetration reaching 1.0% in 2023.
According to CASA data, the overall output value of the third generation of semiconductors in mainland China will exceed 710 billion yuan in 2020. Among them, the output value of SiC and GaN power electronics reached 4.47 billion yuan, a year-on-year increase of 54%; The output value of GaN microwave RF reached 6.08 billion yuan, a year-on-year increase of 80.3%.
It is reported that overall, the difference between domestic and overseas technology generation of wide bandgap semiconductors is not large. "In terms of SiC materials, 6 inches are the mainstream internationally, 8 inches have begun pilot testing, domestic 6 inches have just been mass-produced, and 8 inches are in the sample research and development stage; In terms of SiC devices, domestic low- and medium-power SiC MOSFETs are in the stage of small batch supply, and their performance in terms of high withstand voltage, high thick film epitaxy, and extreme dynamic reliability is lower than the international level, and there is still a certain gap between large-scale manufacturing capacity and STMicroelectronics and CREE. An internal executive of a listed company involved in the third-generation semiconductor business told First Finance and Economics that in terms of GaN, domestic companies and international leaders are basically synchronized in terms of key indicators of materials and devices, but there is a certain gap between the devices and the international level in terms of dynamic characteristics, long-term reliability, and defect control.
Li Long, chief analyst of CCID Consulting New Materials Industry Research Center, recently said at the 2022 World Semiconductor Conference that the third-generation semiconductor industry is still in the early stage of development overall, and if any player can achieve a technological breakthrough, it can change the current market structure, and the third-generation semiconductor has become an important area for related companies to change lanes and overtake.
The largest application market for SiC devices is in new energy vehicles
The SiC industry chain can be roughly divided into three major links: substrate, epitaxy and device, and the device includes design, manufacturing, packaging and testing.
SiC devices cannot be directly fabricated on the substrate, and the required thin film material needs to be generated on the substrate surface by chemical vapor deposition to form epitaxial wafers, and then further made into the device. From the perspective of technical difficulty, the substrate link is the most technically difficult, followed by the device link. The substrate is also the link with the highest proportion of costs, accounting for 47%.
The difficulty of substrate technology is first due to the low yield. There are more than 200 crystal forms of silicon carbide, and to generate the required single crystal form (mainly 4H crystal form), it is necessary to control very precisely. On the other hand, SiC substrate has a hardness of 9.2 on the Mohs scale, which is a high-hardness brittle material, which is easy to crack during processing, and the substrate after processing is prone to quality problems such as warping.
Tianyue Advanced (688234. SH) prospectus shows that from 2018 to 2020 and the first half of 2021, the company's crystal rod yield is 41%, 38.57%, 50.73% and 49.90%, the substrate yield is 72.61%, 75.15%, 70.44% and 75.47%, respectively, and the comprehensive yield is about 37.7%.
The harsh preparation conditions also raise the threshold for substrate preparation. The production of SiC crystal rods requires a high temperature of 2500 °C, while silicon crystals only need 1500 °C, so SiC crystal rods require special single crystal furnaces and precise temperature control; The production cycle of SiC crystal rods is 7 to 10 days, the length is about 2cm, while silicon crystal rods only need 3~4 days to grow, and the length can reach 2m.
"Crystal growth is the most difficult part of SiC technology." The executives of the above-mentioned listed companies told CBN that increasing wafer size and improving the yield of long crystals and processing links are effective ways to reduce costs; The thermal field design, crystal growth and processing process optimization of the long crystal furnace can effectively improve the yield.
"From the perspective of the entire industrial chain, at present, the domestic SiC substrate is relatively mature, although there are still some gaps with foreign countries in terms of yield and size, but the integrity of the entire supply chain can be guaranteed." Liu Zhu, deputy director of the compound product department of CETC 55, said that from epitaxy to process manufacturing to final packaging and testing, the mainland has complete capabilities, and domestic products can currently cover below 3 mm wave band.
SiC applications are mainly divided into RF devices (5G, national defense, etc.) and power devices (new energy, etc.). Among them, new energy vehicles are the largest application market for SiC devices, and according to Yole's forecast, their share will exceed 50% in 2025. Haitong Securities believes that with the continuous replacement and penetration of SiC components in electric vehicles, the value of SiC in bicycles will gradually increase.
From the perspective of supply and demand, according to the research and summary of some market departments, industry insiders believe that the global SiC substrate production in 2025 will total 2.82 million pieces, including 890,000 pieces in China and 1.93 million pieces outside China, while the demand in the conservative case is 3.65 million pieces and 7.28 million pieces in the optimistic case. This means that SiC will be in short supply by then.
"At present, the biggest obstacle to the large-scale commercial use of SiC and GaN devices is product cost performance." The above-mentioned executives told First Finance and Economics that SiC diodes have been commercialized on a large scale, and some domestic companies of SiC MOS devices have achieved technological breakthroughs, and they need to continue to optimize large-scale manufacturing capabilities.
From the perspective of the industrial chain, the current listed companies with SiC layout in China can be roughly divided into five categories: 1) Focus on substrate materials, such as Tianyue Advanced, the domestic semi-insulating SiC substrate leader, and Tianke Heda, which has the largest market share of conductive substrates in China; 2) Device-side IDM, such as China Resources Micro (688396. SH), Star Semiconductor (603290. SH), Wingtech Technology (600745. SH), etc.; 3) Integrated layout of materials to devices, such as Sanan Optoelectronics; 4) Chip design manufacturers, such as Xinjieneng (605111. SH）； 5) Upstream equipment manufacturers, such as Roshow Technology (002617. SZ) layout equipment and materials, AMEC (688012. SH) layout epitaxial equipment.
Among them, Sanan Optoelectronics' SiC business is completed by Hunan Sanan Semiconductor, with a total investment of 16 billion yuan and a planned annual supporting capacity of 360,000 6-inch SiC wafers, covering the entire SiC industry chain, including long crystals, substrates, epitaxy, chip manufacturing and packaging and testing. The first phase has been completed in June 2021, and the second phase is expected to be completed in 2024.
The domestic GaN industry chain has accelerated its layout
GaN materials offer multiple performance advantages. First, GaN can further increase the switching frequency, which means that the volume and area of the system material can be reduced, and secondly, the high saturation electron concentration of GaN can greatly reduce the pilot loss and realize the design of power devices in a small size.
"Compared with 650V GaN devices and SiC devices, the former is about 1/2 or even smaller." Sun Yi, senior vice president of Innosec (Zhuhai) Technology Co., Ltd., said that gallium nitride is the best solution to solve the contradiction of future development.
The application of GaN in the field of fast charging has been proven. According to Yole, consumer electronics accounted for 63.2% of the downstream applications of GaN power devices in 2021, mainly consumer fast charging applications.
However, due to technical constraints, it is still difficult for current GaN devices to be used in high-power scenarios above 10KW and 1200V. Taking new energy vehicles as an example, GaN devices are currently mostly used in low-power scenarios such as DCDC and OBC, and are difficult to implement applications in motor controllers. Therefore, SiC MOSFETs focus on high-voltage areas, and GaN MOSFETs focus on high-frequency areas.
GaN MOSFETs are widely used in the field of 5G RF due to their ultra-high frequency characteristics. Liu Zhu said that after more than 30 years of development, the current level of GaN RF devices in the mainland has basically kept pace with foreign countries, and even led in some new technologies or new designs.
"GaN power electronics products have been applied on a large scale in the field of fast charging, and it is necessary to further improve the operating voltage and reliability, continue to develop in the direction of high power density, high frequency and high integration, and further expand the application field." The above executive said bluntly.
The classification of GaN industry chain players is similar to SiC, and overseas companies are more leading in GaN power semiconductor technology and production capacity, including Infineon, Qorvo, etc.
The domestic GaN industry chain is also accelerating. Domestic enterprises have laid out in the fields of substrate, epitaxy, design and manufacturing, including GaN substrate manufacturers Suzhou Navitas and Dongguan Zhonggallium; epitaxial manufacturers Jingzhan Semiconductor and Jiangsu Nenghua; design companies Amplon, HiSilicon Semiconductor; Manufacturing enterprises Sanan Integration, Highway Huaxin, etc.
This article does not constitute any investment advice, and investors do so at their own risk. The market is risky, and investment needs to be cautious.