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【Domestic News】Development overview of global gallium oxide industry and its inspiration for China
日期：2023-12-15阅读：268
Introduction
Wide band gap semiconductors often have the characteristics of high breakdown field strength, high electron saturation speed and strong radiation resistance. Under the background of the intensified game in the global semiconductor industry, they have continuously attracted high attention from the industry in recent years. Wide band gap semiconductor materials are mainly represented by gallium nitride (GaN), silicon carbide (SiC), zinc oxide (ZnO), gallium oxide (Ga2O3) and diamond materials. Among them, gallium oxide is a new generation of semiconductor materials, as its Baliga’s figure of merit --low loss index (3444)-- is much higher than SiC (340) and GaN (870). Therefore, devices prepared by gallium oxide are expected to have smaller size, lower cost and lower device loss, and are expected to play an important role in the field of power semiconductors in the future. In the process of accelerating the transformation and upgrading of China's traditional industries to become digital, intelligent and green, As a new driving force for the development of the semiconductor industry, if breakthrough is made in key generic technologies in the industry, gallium oxide will be deeply integrated into the development wave of global wide-band gap semiconductor, just like gallium nitride and silicon carbide. In the future, it is expected to accelerate the penetration in new energy, industrial control, frequency conversion home appliances, data center, 5G, IoT and other fields.
Development Status
1.1 From the perspective of regional development pattern, driven by its own advantages and market prospects, Japan and America and other countries are stepping up research and development and layout
（1）Japan has global leading capabilities in the substrate, extension, devices and other industrial chains. For example, NCT and FLOSFIA are the companies leading the development of gallium oxide industry in Japan. NCT has now achieved a mass supply of 2-inch and 4-inch substrates and epitaxial wafers, and in July 2022 announced plans to produce 20,000 wafers of 4-inch per year in 2025. In addition, FLOSFIA has successfully prepared Schottky diodes with the world's smallest conduction resistance using spray chemical vapor deposition, which has been tested in Japan Denso, and is expected to provide auto parts manufacturers with hundreds of thousands of production capacity per month in 2023.
（2）The United States has basically formed the research basis for all links of the gallium oxide industry chain. For example, the United States Air Force Laboratory has prepared a high voltage resistant enhanced gallium oxide MOSFET. The supply of gallium oxide substrates and epitaxial wafers can also be provided by Kyma Technologies, mainly funded by the Department of Energy's Advanced Energy Research Program.
（3）Other countries, such as Leibniz Crystal Growth Institute in Germany, Saint-Gobai in France, have joined the development of gallium oxide material devices. The development of gallium oxide in China is mainly based on scientific research units. With the development of wide band gap semiconductor, some start-ups have emerged, but the industrialization progress is slow.
1.2 From the perspective of the technical development path, Edge-defined Film-fed Growth is the main technical scheme for preparing β-gallium oxide substrate, and the iridium-free method is expected to become the new choice.
The gallium oxide industry chain includes substrate preparation, epitaxial layer growth, device development and downstream applications. At present,substrate preparation is the core difficulty and the link with the highest value of the industrial chain. Substrate preparation is mainly manifested in the substrate crystal type and the process scheme: ① In terms of substrate crystal type growth, gallium oxide has five isomers of α, β, γ, ε and δ, and β -gallium oxide is the most stable phase. ② In terms of substrate crystal growth process, β-gallium oxide single crystal substrate can be grown based on a variety of melt methods including FZ, EFG and CZ methods. Among them, EFG is an extension and supplement of the traditional CZ method, which has the advantages of close size growth, heterogeneous crystal growth, fast growth rate and low processing cost, and has become the mainstream technology scheme of β-gallium oxide in the industry.
In recent years, Tohoku University in Japan in collaboration with start-up C & A, and China Evolution Semiconductor both have proposed molten iridium-free technology solutions. Iridium-free technology does not need to use expensive iridium crucible, which will significantly reduce the cost of material preparation, and significantly improve the material growth efficiency. Iridium-free melt method is expected to become a new technical path for preparing gallium oxide substrate in the future.
1.3 From the perspective of the industrial chain, gallium is widely used downstream, and China's upstream gallium reserves occupy an absolute dominant position in the world.
At present, gallium is widely used in the fields of light-emitting devices, microwave communication, new display and other fields. It is expected to have a great application prospect in the field of integrated circuit in the future, and is becoming a new grain in the electronic industry. For example, gallium nitride (GaN) and indium nitride (InGaN) have become the LED mature technology solutions. GaN also has broad application prospects in mobile phone fast charging and 5G communication. Gallium arsenide (GaAs), as a representative of the second generation of semiconductor materials, has been widely used in microwave devices and high-speed digital circuits with the characters of high frequency, high speed, high temperature and irradiation-resistant. Thanks to the advantages of high mobility and good uniformity, indium gallium zinc oxygen (IGZO) oxide semiconductor has accelerated penetration in large size panels in recent years. In addition, the field-effect transistor (FET) prepared with IGZO as an active layer has great potential in various large-scale integrated circuits (LSI) fields such as integrated circuit back end of line (IC-BEOL), normally close CPU (the transistor threshold voltage is positive, enhanced device), DRAM / NAND and FPGA. As a companion mineral, the content of gallium in the crust is 5×10^(-4)%~1.5×10^(-3) %, which is a typical dilute element . According to statistics, the global total reserves of gallium are 23 0,000 tons, and China accounts for more than 80% of the total as the largest producer of gallium in the world, mainly supplying for the United States, the European Union, Japan and South Korea.
Opportunities and challenges
2.1 Opportunities for industrial development
2.1.1 Power devices do not follow Moore's Law, bringing long and long-time opportunities for industrial development
The development of integrated circuit devices in the manufacturing process level mainly includes two major directions: size-dependent advanced process and non-size-dependent characteristic process. In the longitudinal advanced process, the reduction of device feature size, the reduction of working voltage and the improvement of switching frequency have become the goals of the industry. In the horizontal characteristic process, the diversification of device structure, how the chip can withstand high voltage, high output current, improve circuit linear characteristics and reduce noise and other characteristic parameters become the main development direction. In the future, gallium oxide will be mainly used in Schottky diodes, power MOSFET and other power semiconductors. It belongs to the characteristic process manufacturing, strongly depending on material quality, preparation process and device structure. There is no obvious microscaling requirements for the transistor channel length, generally using 0.18-0.5 μ m process. Device evolution does not need to follow Moore's Law, which presents a long-term opportunity for gallium oxide development.
2.1.2 The superposition of high performance and low cost advantages brings new opportunities for industrial development
（1）From the perspective of material and device performance, the band width of gallium oxide is about 4.9 eV, and its theoretical breakdown field strength is 8 MV / cm. The wider band width of gallium oxide can withstand stronger electric fields than silicon, silicon carbide and gallium nitride, bringing a significant competitive advantage for power devices against high voltage and small volume.
（2）From the perspective of the cost of material and device, in the raw material link, the price of gallium oxide powder is about 2000-3000 yuan / kg, and the high purity silicon carbide powder reaches tens of thousands of yuan / kg. In the preparation process of single crystal substrate, the growth cycle of gallium oxide single crystal substrate is generally shorter than that of silicon carbide, and the efficiency of producing gallium oxide by the international leading enterprises is generally 2 times faster than that of silicon carbide. If iridium-free melt technology is succeeded, the growth efficiency will be greatly improved. In the link of device produce, it is estimated that if gallium oxide devices achieve mass production, compared with devices based on a 6-inch substrate from the perspective of the cost composition, the cost of gallium oxide material-based devices is about 8000 yuan , which is about 1 / 4 of the cost of silicon carbide devices.
2.1.3The strategy of peak carbon dioxide em-missions and carbon neutrality has been advanced steadily, bringing historic opportunities for industrial development
Compared with silicon carbide, gallium oxide has significant energy saving advantages in raw material processing, substrate epitaxy and device performance.
（1）In terms of raw materials, the preparation process of gallium oxide powder is more simple than that of silicon carbide powder. Silicon carbide powder has high purity requirements and is difficult to purify, which will further increase energy consumption.
（2）In terms of substrate material growth, according to a simple calculation, when the yield is ideal, growing a 4-inch gallium oxide substrate via EFG method consumes about 100kW.h of electricity, while the physical vapor transmission method (PVT) requires at least 300kW.h of electricity to grow a 4-inch piece of silicon carbide. And the hardness of silicon carbide leads to the ingot of more electricity in the process of grinding.
（3）In terms of device performance, The conduction characteristics of gallium oxide devices are ten times that of silicon carbide, and the switching loss is half that of silicon carbide, which brings lower conduction loss and higher power conversion efficiency of gallium oxide devices. Gallium oxide will become an important global tool to promote the green and low-carbon transformation of manufacturing industry.
2.2 Challenges facing industrial development
2.2.1Restricted by the early stage of industrial development, the technological development still needs to achieve a breakthrough in key difficulties.
In recent years, although there are global enterprises layout of gallium oxide, but in terms of technology maturity, application scale and peripheral ecology, it is still in the early stage of industrial development, and the key core technologies still need to be further breakthrough. The main technical difficulties are presented as follows:
（1）In terms of the substrate growth, first, the melting point of β-Ga2O3 grown via EFG is 1820℃. In the process of high temperature growth, a large number of oxygen vacancies are easily produced, resulting in defects such as twin crystal, mosaic structure and spiral dislocation. Second, the substances such as Ga (g), GaO (g), GaO2 (g) and O2(g) decomposed at high temperature will seriously corrode the iridium crucible . In terms of material epitaxy, it is difficult to accurately regulate the n-type doping of gallium oxide due to the high concentration of gallium oxide background carriers.
（2）In terms of device performance, first, the thermal conductivity of gallium oxide is only one tenth of that of silicon carbide and one fifth of silicon. The low thermal conductivity causes a lot of heat retention when the device works, which will greatly limit the device life [1]. Second, it is difficult for p-type doping of gallium oxide film, which brings challenging to form bipolar type and CMOS devices.
2.2.2 Affected by the diverse supply of material system, high-power devices will face fierce competition in the future
At present, the trend of power semiconductor evolution to wider bandgap is more and more obvious. In the future, high power devices will compete with silicon base, silicon carbide and gallium oxide. The analysis of competition are as follows:
One is the competition brought about by the silicon-based IGBT. Due to the advantages of insulated gate bipolar transistors (IGBT)--the high input impedance of metal-oxide semiconductor field-effect transistors (MOSFET) and the low conduction voltage drop of BJT, IGBT has driven downstream applications in new energy vehicles, photovoltaic inverters and energy storage in recent years, and its demand is strong. The global IGBT market is expected to grow from $7.2 billion in 2021 to $17.9 billion in 2030, according to BrainyInsights forecasts.
The second is the competition brought about by the accelerated penetration of silicon carbide devices. Due to its high voltage, low loss and high switching performance, silicon carbide is accelerating its penetration into new energy vehicles and photovoltaic power generation fields. According to Grand View Research, the global silicon carbide device market will reach $7.98 billion by 2030.
Third, gallium oxide will earn its spur in the future power semiconductor market. According to Fujifilm Economy, the market size for gallium oxide power devices will reach $1.5 billion by 2030.
2.2.3 Due to the further enhancement of the future value, the leading countries are tightening the control of gallium oxide
Gallium oxide has the characteristics of enduring high voltage, strong piezoelectric polarization coefficient and radiation resistance, and has important application value in high voltage power control, mobile communication radio frequency and flame detection (such as missile tail flame). To this end, leading countries have strengthened their control in recent years.
（1）Japan's Ministry of Economy, Trade and Industry (METI) has been revising its "end-user list" of export controls, hindering the national procurement of gallium oxide substrates and epitaxial wafers.
（2）In December 2021, the Wassenaer Agreement (WA) issued a revised regulatory list, adding gallium oxide and diamond to the three items of semiconductor substrate, high resistance material substrate and substrate epitaxial layer.
（3）In August 2022, the Commerce Department's Bureau of Industry and Safety (BIS) of America imposed new export controls on gallium oxide technology. The above control action brought great impact for the later pursuers to realize the high-quality development of gallium oxide industry and high-level safety interaction.
Inspiration
3.1 Special funds should be set up to accelerate technological breakthroughs in key industrial links
First, the government can increase financial support for the research and development of key technologies, recruit excellent R&D teams and talents at home and abroad, aim at the substrate preparation and extension link of the gallium oxide industry chain, and focus on the breakthrough of the "iridium-free method" preparation technology of gallium oxide substrate, gallium oxide polishing and grinding technology and the development of hydride vapor phase epitaxy (HVPE) equipment. Second, the government should support qualified enterprises or institutions to carry out the construction of test lines. Using the "horse racing" mechanism, try to select and support 1-2 "pioneer" enterprises that can achieve the mass production of gallium oxide substrate within 5 years.
3.2 Downstream applications should be cultivated and the gallium oxide semiconductor industry ecology should be expanded
First, gallium oxide planning policies is supposed to introduced from the nation, to mobilize key enterprises, universities and institutions, industrial service institutions, industry associations, industrial alliances, national financial institutions, social capital and other social resources, to improve the new potential energy for the development of the semiconductor gallium oxide industry.
Second, with the market as the guidance and enterprises as the main body, to create an innovation ecology of close cooperation between "government, industry, university, research and capital". Support key enterprises in the industry in cooperating with universities, research institutes and upstream and downstream enterprises to build manufacturing innovation centers, undertake major national science and technology projects, and accelerate the incubation of downstream gallium oxide application enterprises.
3.3 Strengthen risk awareness, grasp the initiative of gallium oxide industry development
First, strengthen the layout of key nodes of the gallium oxide supply chain, and guide domestic competitive enterprises to undertake the research and development tasks of equipment and parts, materials and raw materials, design tools, testing equipment, factory facilities and other links.
Second, encourage domestic enterprises or institutions to implement the global distribution of gallium oxide intellectual property rights, actively set up barriers, form a multiple set of trade secrets and patent "combination", and improve the discourse power in all links of China's gallium oxide supply chain.
Conclusion
Due to the obvious advantages of gallium oxide, the governments of various scientific and technological powers attach great importance to the investment in gallium oxide, and the key enterprises in the field of wide band gap semiconductor also pay close attention to the global development status and future trend of gallium oxide. Gallium oxide has a larger band gap width than silicon carbide and gallium nitride, and the material has great advantages in high power and low loss semiconductor device preparation. In the future, it has huge potential applications in aerospace, 5G communication, new energy vehicles, rail transit, high-end equipment, smart grid and many other fields, and has broad market prospects. Power devices prepared by gallium oxide materials will play a key role in promoting the upgrading of China's industrial structure, energy conservation and emission reduction. Chinese government, key enterprises, universities and institutes, industrial service institutions, national financial institutions, social capital and other social resource factors should be closely coordinated, so as to inject new momentum for China's semiconductor industry to achieve cutting-edge technology guidance and power semiconductor industry and become bigger and stronger as soon as possible.
Author information
Ma Yaibin, Shi Jian, Zhao Cong Peng, Ge Jie
Researchers in Integrated Circuit Research Institute Think Tank, China Electronic Information Industry Development Research Institute
Source: China Integrated Circuit 2023,32(07)
