The Japanese Ministry of Economy, Trade and Industry (METI) plans to provide financial support to private companies and universities dedicated to the development of a new generation of low-energy semiconductor material "gallium oxide". The report pointed out that METI will set aside approximately US$20.3 million next year to fund related enterprises. It is estimated that the funding for Ghost Mother will exceed US$85.6 million in the next five years.
As we all know, Japan's advantages in the semiconductor field, which has undergone the "Plaza Agreement" between Japan and the United States, have been completely transferred to materials and equipment. For example, in terms of silicon wafers, several Japanese companies are among the best, and various gases and compounds used in the production of semiconductor chips On the one hand, Japan does not give up too much. Regarding EUV lithography frequently mentioned by domestic media recently, although Japan does not provide corresponding lithography machines, they almost monopolize the global EUV photoresist supply, so their optimistic semiconductor materials have certain representative significance. of.
Here, let's take a closer look at what this semiconductor material is promising in Japan.
What is gallium oxide?
Data show that gallium oxide (Ga2O3) is an emerging ultra-wide band gap (UWBG) semiconductor with an ultra-large band gap of 4.8eV. In contrast, the band gap of SiC and GaN is 3.3eV, while silicon is only 1.1eV, which allows this new material to have higher thermal stability, higher voltage, and its ability to be widely adopted. The natural substrate allows developers to easily develop miniaturized, high-efficiency high-power transistors based on this. This is why Ga2O3 still attracts wide interest from developers when great progress has been made in wide band gap (WBG) semiconductor devices represented by SiC and GaN.
From the device point of view, the Baliga quality factor of Ga2O3 is twenty times higher than that of SiC. For various applications, the band gap of ceramic oxide is about 5 eV, which is much higher than the band gap of SiC and GaN, and the latter two are less than 3.5 eV. Therefore, this ceramic oxide device can withstand higher operating voltages than SiC or GaN devices, and the on-resistance is also lower.
From another perspective, the easy-to-manufacture natural substrate, the control of the carrier concentration and the inherent thermal stability also promote the development of Ga2O3 devices. Related papers show that when Ga2O3 is doped with Si or Sn in N-type, good controllability can be achieved. Although some UWBG semiconductors (such as AlN, c-BN and diamond) beat Ga2O3 in the BFOM chart, their widespread use is severely restricted. In other words, AlN, c-BN and diamond still lack suitable substrates for high-quality epitaxial growth.
According to related reports, Ga2O3 has five different phases, among which the α phase has the same corundum crystal structure as Al2O3 or sapphire. This provides research and development for researchers to achieve stress-free Ga2O3 layer deposition on sapphire substrates. Ideas.
Relevant statistics show that from the data point of view, the loss of gallium oxide is theoretically 1/3,000 of silicon, 1/6 of silicon carbide, and 1/3 of gallium nitride. This makes people in the industry have high expectations for its future. And cost is another important factor that makes it an attracting industry attention.
According to the global market forecast of wide-bandgap power semiconductor components announced by the market research company Fuji Keizai on June 5, 2019, the market size of gallium oxide power components in 2030 will reach 154.2 billion yen (approximately RMB 9.276 billion). Yuan), the market scale is larger than the 108.5 billion yen scale of GaN power devices.
Industry leader
Since this material has such leading performance, naturally many companies around the world have invested in it. Let’s look at Japan first. According to observations in the semiconductor industry, Flosfia invested by Kyoto University, NICT, and Novel Crystal invested by Tamura are the leading Ga2O3 suppliers.
Relevant information shows that Flosfia was founded in March 2011 by Kyoto University researchers Toshimi Hitora, Shizuo Fujita and Kentaro Kaneko. It is different from the method research on GaN or SiC epitaxial growth in other parts of the world. Flosfia researchers developed a A new type of preparation method, which is to prepare a power device by depositing a gallium oxide layer on a sapphire substrate. This mainly relies on a chemical vapor deposition process called "Mist Epitaxy" (spray drying method).
We know that the traditional Chemical Vapor Deposition; CVD is to produce the required film through the chemical reaction between the reaction gases in a vacuum state, but it is difficult to enlarge the area, and the cost is also one of the problems. But the Mist Epitaxy used by Flosfia atomizes the liquid before applying it to the film forming process. Since the raw material is liquid, the selectivity of the raw material is greatly improved, and the large area becomes feasible without the need for vacuum processing, which helps to reduce the cost.
According to the official Flosfia, the MISTDRY technology they produced enables them to manufacture diodes and transistors based on gallium oxide, and these diodes and transistors require only one-tenth less power than the previous volume.
It can be seen from the official website that the Schottky barrier diode (SBD) that the company first released in 2015 has been sampled, and the on-resistance of its 521V withstand voltage device is only 0.1mΩcm2, and the on-resistance of the 855V withstand voltage SBD It is only 0.4mΩcm2. This is enough to witness the advantages of these devices.
Because of the material properties, some experts believe that gallium oxide cannot be used to make P-type semiconductors. However, Shizuo Fujita of Kyoto University and Flosfia successfully developed a Ga2O3 insulation effect transistor (MOSFET) with a sapphire structure in 2018. According to the results of this research, the miniaturization of power converters may reach a few tenths and reduce costs. The effect is expected to reach 50% of the total power converter. This makes this technology and products expected to be used in various power sources that require safety, and is expected to support the popularization of electric vehicles and small AC adapters.
Also in 2018, Denso and Flosfia decided to jointly develop gallium oxide (α-Ga2O3), a next-generation Power semiconductor material for automotive applications. According to Denso, through the joint development of gallium oxide (α-Ga2O3) for vehicles by the two companies, the technological innovation of PCU, the main unit of vehicle electrification, is just around the corner. This technology will play a positive role in the lighter development of electric vehicles and the improvement of fuel costs, so as to realize the harmonious coexistence of people, vehicles and the environment.
As can be seen from Flosfia's report, they also plan to expand this year and achieve mass production.
Novel Crystal Technology (hereinafter referred to as NCT) was established in 2015. The company's solution is based on HVPE-grown Ga2O3 planar epitaxial chips. Their goal is to accelerate the product development of ultra-low loss, low-cost β-Ga2O3 power devices. Developed β-Ga2O3 power device.
According to data, NCT has successfully developed, manufactured and sold gallium oxide wafers with a maximum diameter of 4 inches. In November 2017, Nove Crystal Technology and Tamura Corporation successfully developed the world's first trench MOS power transistor made of gallium oxide epitaxial film, which consumes only 1/1000 of the traditional silicon MOSFET.
According to their plan, starting from the second half of fiscal year 2019, NCT will begin to provide 10-30 A samples of β-Ga2O3 trench SBD with a breakdown voltage of 650-V. They also intend to advance preparations for mass production from 2021. The company is also committed to the rapid development of 100A-level β-Ga2O3 power devices.
Since 2012, the industry has continuously announced the research and development and trial production results of galvanic oxide power components. So far, we have tried horizontal MES FET, horizontal MOS FET, and vertical MIS FET of Normally Off. In SBD experiments, it has been proved that the on-resistance of gallium nitride devices is much lower than that of silicon carbide SBD! It can be proved that its performance exceeds silicon carbide power components in the preliminary test stage. The number of Japanese companies participating in research and development continues to increase.
Coming to the United States, in June of this year, the University at Buffalo is developing a transistor based on gallium oxide. According to them, a device based on this transistor can handle 8000V or more. Voltage, and only as thin as a sheet of paper. It can help create smaller and more efficient electronic systems for use in electric vehicles, locomotives and airplanes.
In addition, researchers from the University of Florida, the US Naval Research Laboratory and Korean University are also studying gallium oxide MOSFETs. Stephen Pearton, professor of materials science and engineering at the University of Florida, said that they are optimistic about the development potential of gallium oxide as a MOSFET.