Because the third-generation semiconductor materials have very significant performance advantages and a huge industry leading role, developed countries and regions such as Europe, America and Japan have included the development of silicon carbide semiconductor technology in their national strategies and invested heavily in supporting development. This article will analyze the definition and characteristics of third-generation semiconductor materials in detail, as well as the research and development status of various countries.
1. Overview of the first generation of semiconductor materials
The first-generation semiconductor materials mainly refer to silicon (Si) and germanium (Ge) semiconductor materials. As the first generation of semiconductor materials, germanium and silicon, various discrete devices and applications in the international information industry technology are extremely common integrated circuits, electronic information network engineering, computers, mobile phones, televisions, aerospace, various military engineering and rapid The development of new energy and silicon photovoltaic industries have been extremely widely used, and silicon chips are shining with its brilliance in every corner of human society.
2. Overview of second-generation semiconductor materials
The second-generation semiconductor materials mainly refer to compound semiconductor materials, such as gallium arsenide (GaAs) and indium antimonide (InSb); ternary compound semiconductors, such as GaAsAl, GaAsP; and some solid solution semiconductors, such as Ge-Si, GaAs- GaP; glass semiconductors (also known as amorphous semiconductors), such as amorphous silicon, glassy oxide semiconductors; organic semiconductors, such as phthalocyanine, copper phthalocyanine, polyacrylonitrile, etc.
The second-generation semiconductor materials are mainly used to make high-speed, high-frequency, high-power and light-emitting electronic devices, and are excellent materials for making high-performance microwave, millimeter wave devices and light-emitting devices. Due to the rise of the information highway and the Internet, it has also been widely used in satellite communications, mobile communications, optical communications, and GPS navigation.
3. Third-generation semiconductor materials
1. Definition
The third-generation semiconductor materials are mainly semiconductor materials with wide bandgap (Eg>2.3eV) represented by silicon carbide (SiC), gallium nitride (GaN), zinc oxide (ZnO), diamond, and aluminum nitride (AlN).
2. Application field
The third-generation semiconductor materials represented by SiC, etc., will be widely used in optoelectronic devices, power electronic devices and other fields. With their excellent semiconductor properties, they will play an important innovative role in various modern industrial fields, and their application prospects and market potential are huge.
With the reduction of SiC production costs, SiC semiconductors are gradually replacing Si semiconductors with their excellent performance, breaking the bottleneck encountered by Si-based materials due to the properties of the materials themselves. Undoubtedly, it will trigger an industrial revolution similar to the steam engine:
1. SiC material is used in the field of high-speed rail, which can save energy by more than 20% and reduce the volume of the power system;
2. The application of SiC materials in the field of new energy vehicles can reduce energy consumption by 20%;
3. SiC material is used in the field of home appliances, which can save energy by 50%;
4. SiC materials are used in the field of wind power generation, which can increase the efficiency by 20%;
5. SiC materials are used in the solar energy field, which can reduce the photoelectric conversion loss by more than 25%;
6. SiC materials are used in the field of industrial motors, which can save energy by 30%-50%;
7. SiC materials are used in the field of ultra-high voltage DC power transmission and smart grids, which can reduce power loss by 60% and increase power supply efficiency by more than 40%;
8. The application of SiC material in the field of big data can help data center energy consumption to be greatly reduced;
9. The application of SiC material in the field of communication can significantly improve signal transmission efficiency and transmission safety and stability;
10. SiC materials can reduce the loss of equipment by 30%-50% in the aerospace field, increase the operating frequency by 3 times, reduce the volume of inductors and capacitors by 3 times, and greatly reduce the weight of the radiator.
3. Material characteristics
Compared with the first and second generation semiconductor materials, the third generation semiconductor materials have a wider band gap, higher breakdown electric field, higher thermal conductivity, higher electron saturation rate and higher radiation resistance. , More suitable for the production of high-temperature, high-frequency, anti-radiation and high-power devices, usually referred to as wide band gap semiconductor materials (band gap greater than 2.2 electron volts), also known as high temperature semiconductor materials. From the current research on third-generation semiconductor materials and devices, SiC and GaN semiconductor materials are more mature, while research on materials such as zinc oxide, diamond, and aluminum nitride is still in its infancy.
Compared with Si, SiC has many advantages: 10 times the electric field strength, 3 times the thermal conductivity, 3 times the band gap width, and 1 times the saturation drift speed. Because of these characteristics, devices made of SiC can be used in extreme environmental conditions. Microwave and high-frequency and short-wavelength devices are currently mature application markets. The 42GHz frequency SiCMESFET is used in military phased array radars and communication and broadcasting systems. The high-brightness blue LED with SiC as the substrate is a key device for full-color large-area display screens.
Doping silicon carbide SiC with nitrogen or phosphorus can form an n-type semiconductor, while doping with aluminum, boron, gallium, or beryllium forms a p-type semiconductor. Doping a large amount of boron, aluminum or nitrogen in silicon carbide can make the doped silicon carbide possess an electrical conductivity comparable to that of metal. Al-doped 3C-SiC, B-doped 3C-SiC and 6H-SiC silicon carbide can all have superconductivity at a temperature of 1.5K, but the magnetic field behavior of both Al and B-doped silicon carbide has Obvious difference. Aluminum-doped silicon carbide and B-doped crystalline silicon are both type II semiconductors, but boron-doped silicon carbide is a type I semiconductor.
Gallium nitride (GaN, Gallium nitride) is a compound of nitrogen and gallium. The structure of this compound is similar to wurtzite and has high hardness. As an emerging semiconductor process technology, it provides multiple advantages over silicon. Compared with silicon devices, GaN has achieved a performance leap in power conversion efficiency and power density.
GaN has excellent breakdown capability, higher electron density and speed, and higher operating temperature. Gallium nitride has a wide energy gap of 3.4 electron volts, and is widely used in power factor correction (PFC), soft-switching DC-DC and other power system designs, as well as power adapters, photovoltaic inverters or solar inverters, servers and Communication power supply and other terminal fields.
GaN is an extremely stable compound and a hard high melting point material with a melting point of about 1700°C. GaN has a high degree of ionization, which is the highest (0.5 or 0.43) among III-V compounds. Under atmospheric pressure, GaN crystals generally have a hexagonal wurtzite structure. It has 4 atoms in a cell, and the atomic volume is about half of GaAs. Because of its high hardness, it is also a good coating protection material.
The electrical characteristics of GaN are the main factors affecting the device. Unintentionally doped GaN is n-type in all cases, and the electron concentration of the best sample is about 4×1016/cm3. In general, the prepared P-type samples are highly compensated.
4. Representative countries
For example, in the United States, in early 2014, US President Barack Obama announced the establishment of the "Next Generation Power Electronics Technology National Manufacturing Innovation Center", hoping to strengthen the R&D and industrialization of third-generation semiconductor technologies to enable the United States to occupy the emerging power electronics industry of the next generation. The largest and fastest-growing emerging markets have created a large number of high-income jobs for the United States.
Japan has also established the "Next Generation Power Semiconductor Packaging Technology Development Alliance", led by Osaka University, in collaboration with 18 well-known companies engaged in the development and industrialization of SiC and GaN materials, devices, and application technologies, including Roma, Mitsubishi Electric, and Matsushita Electric. Universities and research centers jointly develop advanced packaging technologies that adapt to the characteristics of next-generation power semiconductors such as SiC and GaN.
Europe launched the industry-university-research project "LASTPOWER", led by STMicroelectronics, and coordinated with private companies, universities and public research centers from six European countries including Italy and Germany to jointly research key technologies of SiC and GaN. Through the research and development of cost-effective and highly reliable SiC and GaN power electronics technologies, the project puts Europe at the forefront of the research and commercialization of energy-efficient power chips in the world.
In May 2015, China established the third-generation semiconductor materials and application joint innovation base to seize the strategic new heights of the third-generation semiconductors. It also signed a strategic cooperation agreement with Delft University of Technology in the Netherlands, marking the introduction of international superior innovation resources by the base , Gathering global innovative and entrepreneurial talents to make new progress.
In the future, power devices made of semiconductor SiC materials will support the development trend of today's energy-saving technology and become the core component of energy-saving equipment. Therefore, semiconductor SiC power devices are also known by the industry as the "CPU" of power converter devices and green economy. The "core".
5. my country's third-generation semiconductor materials research and development
It is understood that the Chinese government attaches great importance to the research and development of third-generation semiconductor materials. Since 2004, it has deployed research in the field of third-generation semiconductors and initiated a series of major research projects. In 2013, the Ministry of Science and Technology planned new materials in the 863 Program. In the technical field project solicitation guide, the third-generation semiconductor materials and applications are clearly listed as important content.
The industry is generally optimistic about the market development prospects of SiC. According to forecasts, its market size will reach US$4 billion by 2022, with an average annual compound growth rate of 45%, which will give rise to a huge market application space.
Although the prospects are promising, the biggest bottleneck for my country's development in this field is raw materials. The quality and preparation of SiC raw materials in my country need to be solved urgently. At present, there is still a vacancy in the preparation of SiC wafers in my country, and most of the equipment is imported from abroad.
The domestic research work on SiC and GaN materials and devices is relatively late, and the level is low compared with foreign countries. There are also the original innovation problems that hinder the progress of domestic third-generation semiconductor research. Most domestic research institutes and related production companies in the field of new materials are eager for quick success and instant benefits, and cannot tolerate the long-term “only input, no output” status quo. Therefore, the original innovation of new materials represented by the third-generation semiconductor materials is difficult.
The downstream output of the industrial chain must be based on upstream materials. In fact, my country does not pay enough attention to basic material issues. Once the investment and support are not enough, relevant talents will be difficult to attract, and the problem of talent team building will also be Gradually become a development bottleneck.
However, at the first International Symposium on the Development of Third-Generation Semiconductor Materials and Applications, Cao Jianlin, Vice Minister of Science and Technology, once stated, "Today's China has reached the forefront of technology in the world, not to mention that China is already the world's largest economic system. , We should work with colleagues around the world to solve the problems we are facing, and as the Chinese government strengthens its support for innovation and encourages innovation, we believe that China is capable of solving these problems. This is not only for China, but also for the science of the world. Technical work has made a huge boost."
In addition, the participating experts also believe that, unlike the situation where the first and second generation semiconductor materials and integrated circuit industries have been behind for many years and it is difficult to catch up with the international advanced level, China’s research work in the third generation semiconductor field has been closely following the situation. At the forefront of the world, there is not a big gap between the level of engineering technology and the international advanced level. It has developed from tracking and imitation to keeping pace with each other, and then may gain leadership and comparative advantages in some fields, and have the opportunity to achieve beyond.
Therefore, with the increase of national strategic support, especially my country has a relatively good industrial foundation in energy conservation, emission reduction and rapid development of information technology, and has urgent market needs. Therefore, my country is expected to concentrate its advantages in one fell swoop. Overtaking on the road and taking the lead.
