China has successfully developed 6-inch silicon carbide wafers with an annual production capacity of 70,000 pieces.

China has successfully developed 6-inch silicon carbide wafers with an annual production capacity of 70,000 pieces.

Summary:

From 2-inch, 3-inch, 4-inch to the current 6-inch silicon carbide single crystal substrate, the team led by Chen Xiaolong spent over 10 years in China, achieving the first domestic development and industrialization of silicon carbide single crystal substrates. According to a report by China Science Daily on the 12th, not long ago, the research group of Professor Chen Xiaolong from the Institute of Physics of the Chinese Academy of Sciences and Beijing Tianke Hedai Blue Light Semiconductor Co., Ltd. (hereinafter referred to as Tianke Hedai) collaborated to solve the 6-inch widening technology and wafer processing technology, successfully developing 6-inch silicon carbide single crystal substrates. As of March 2014, Tianke Hedai had formed a production line capable of manufacturing 70,000 silicon carbide wafers annually.

Silicon carbide, as a third-generation semiconductor material, can be used to manufacture new-generation high-efficiency and energy-saving power electronic devices and is widely applied in various fields of the national economy, such as air conditioners, photovoltaic power generation, wind power generation, high-efficiency motors, hybrid and pure electric vehicles, high-speed trains, smart grids, ultra-high voltage power transmission and transformation, etc. Compared with traditional silicon devices, using silicon carbide semiconductor power electronic devices can significantly reduce energy loss in the power system, improve power efficiency, reduce the size of the power system, and at the same time increase system reliability and reduce the overall cost of the system. The popularization and application of efficient and energy-saving silicon carbide power electronic devices can provide technical support for industrial upgrading, energy conservation and emission reduction, and the construction of a low-carbon society.

According to the report, the US F-22 fighter jet also extensively uses silicon carbide semiconductor devices. China's silicon carbide technology was earlier applied to military and is now gradually expanding to civilian fields. Once popularized, it will create huge social benefits.

Professor Chen Xiaolong from the Institute of Physics of the Chinese Academy of Sciences

6-inch silicon carbide crystals and single crystal substrates

6-inch silicon carbide crystals and single crystal substrates

Third-generation semiconductor materials

The researchers said that in the 1950s and 1960s, silicon and germanium constituted the first generation of semiconductor materials, mainly used in low-voltage, low-frequency, medium-power transistors and photodetectors. Compared with germanium semiconductor devices, silicon materials manufactured semiconductor devices have better high-temperature and radiation resistance performance.

In the late 1960s, 95% of semiconductors and 99% of integrated circuits were made of silicon semiconductor materials. Until now, most of the semiconductor products we use are based on silicon materials.

After entering the 1990s, gallium arsenide and indium phosphide represented the second generation of semiconductor materials, which could be used to manufacture high-speed, high-frequency, high-power and light-emitting electronic devices. Due to the rise of information highways and the Internet, the second-generation semiconductor materials were widely used in satellite communications, mobile communications, optical communications and GPS navigation, etc.

Compared with the previous two generations of semiconductor materials, the third-generation semiconductor materials are usually called wide bandgap semiconductor materials or high-temperature semiconductor materials. Among them, silicon carbide and gallium nitride are mature representatives of the third-generation semiconductor materials.

The reporter learned that silicon carbide single crystals are a wide bandgap semiconductor material, with large bandgap width, strong critical breakdown field, high thermal conductivity, and high saturation drift velocity, and are widely used in the manufacture of high-temperature, high-frequency and high-power electronic devices.

Regarding gallium nitride, there was a report stating that a 2-inch gallium nitride wafer can produce 10,000 LED lighting lamps with 10 times the brightness of energy-saving lamps, 3 to 4 times the luminous efficiency of energy-saving lamps, and 10 times the lifespan of energy-saving lamps; it can also manufacture 5,000 blue laser devices with an average selling price of around $100. It can also be applied to power electronic devices, reducing system energy consumption by more than 30%.

Due to the small lattice mismatch between silicon carbide and gallium nitride, silicon carbide single crystals are ideal substrate materials for gallium nitride-based LEDs, Schottky diodes, metal-oxide-semiconductor field-effect transistors and other devices. The research group of Chen Xiaolong from the Advanced Materials and Structural Analysis Laboratory of the Institute of Physics has been engaged in the research on silicon carbide single crystal growth for a long time.

The United States leads the world in silicon carbide wafer technology and widely applies it to advanced weapons such as F-22. (Data image)

The United States leads the world in silicon carbide wafer technology and widely applies it to advanced weapons such as F-22. (Data image)

Breakthrough in large-sized wafers

Although the ideal substrate for gallium nitride growth is gallium nitride single crystal material, this material can not only significantly improve the crystal quality of the epitaxial film, reduce dislocation density, but also improve the working life, working current density and light emission efficiency of the device. However, the preparation of gallium nitride bulk single crystal material is very difficult, and so far there is no effective method.

Therefore, researchers have grown gallium nitride thick films on other substrates (such as silicon carbide), and then achieved the separation of the substrate and the gallium nitride thick film through the peeling technology. The separated gallium nitride thick film can be used as the epitaxial substrate. Although the bit error density of the epitaxial growth with gallium nitride thick film is significantly lower than that of the gallium nitride film epitaxially grown on silicon carbide material, it is expensive.

Therefore, Chen Xiaolong's team chose silicon carbide single crystal substrate for research. He pointed out that silicon carbide single crystal substrates have many outstanding advantages, such as good chemical stability, good electrical conductivity, good thermal conductivity, and no absorption of visible light, but also has disadvantages, such as high price.

In the early days, the price of silicon carbide wafers in the global market was very high. The international market price of a 2-inch silicon carbide wafer once reached 500 US dollars (in 2006), but still in short supply. The high raw material cost accounted for more than 10% of the price of silicon carbide semiconductor devices, "The price of silicon carbide wafers has become the bottleneck for the development of the third-generation semiconductor industry," Chen Xiaolong said.

To reduce the cost of devices, the downstream industry has proposed a large-sized requirement for silicon carbide single crystal substrates. Therefore, by adopting advanced silicon carbide crystal growth technology, achieving large-scale production, and reducing the production cost of silicon carbide wafers, it will promote the rapid development of the third-generation semiconductor industry and expand market demand.

Tiankeheeda was established in 2006, relying on the research results of the carbonitride field in Chen Xiaolong's research team. Since its establishment, Tiankeheeda has developed silicon carbide crystal growth furnaces and silicon carbide crystal growth, processing technology and professional equipment, and established a complete silicon carbide wafer production line.

Over the years, Tiankeheeda has been committed to improving the quality of silicon carbide crystals and the research and development of large-sized silicon carbide crystals, industrializing advanced silicon carbide crystal growth and processing technologies, and large-scale production and sales of silicon carbide wafers with independent intellectual property rights.

10 years of independent innovation journey

As a silicon carbide substrate provider, Cree Inc. in the United States once monopolized the international market. In 2011, Cree Inc. released 6-inch silicon carbide crystals, and in the same year, Tiankeheeda began to mass-produce 4-inch silicon carbide crystals.

In 2013, Chen Xiaolong's team began to conduct research on 6-inch silicon carbide crystals, and after nearly a year of work, the domestically produced 6-inch silicon carbide single crystal substrate was launched. Tests proved that the crystallization quality of the domestic 6-inch silicon carbide crystals was very good, and this achievement marked that the research and development of silicon carbide single crystal growth by the Institute of Physics has reached the international advanced level, providing a material basis for the domestic production of high-performance silicon carbide-based electronic devices.

"Although we started a little late, through 10 years of independent research and development, our technical gap with foreign countries is gradually narrowing," Chen Xiaolong said. As a pioneer in the domestic production and manufacturing of silicon carbide wafers, Tianke Hedada has broken the foreign monopoly and filled the domestic gap. The silicon carbide wafers produced by it are not only technologically mature but also cheaper than similar international products.

As of March 2014, Tianke Hedada has established a production line capable of manufacturing 70,000 silicon carbide wafers annually, promoting the continuous and stable development of China's third-generation semiconductor industry and achieving good economic and social benefits.

Chen Xiaolong pointed out that currently, silicon carbide is mainly applied in three fields: high-brightness LED, power electronics, and advanced radar. In the future, it may also enter the household market. This means that the independent innovation and industrialization path of Chen Xiaolong's team will continue.