2024-04-12
In this issue, we delve into the application, preparation process, market size and development trend of silicon carbide epitaxy.
Epitaxy refers to the growth of a layer of higher quality single crystal material on the surface of silicon carbide substrate, and the growth of a layer of silicon carbide epitaxy on the surface of conductive silicon carbide substrate, called homogeneous epitaxy; The growth of gallium nitride epitaxy layer on semi-insulated SIC substrate is called heteroepitaxy. The size of the epitaxial is also the same as the substrate, mainly 2 inches (50mm), 3 inches (75mm), 4 inches (100mm), 6 inches (150mm), 8 inches (200mm) and other specifications.
SiC carbide epitaxy can manufacture all kinds of power devices, which can be used in new energy vehicles, photovoltaic energy storage, aerospace and other fields; Gallium nitride epitaxy can manufacture various RF devices for 5G communication, radar and other fields.
With the growth of demand for silicon carbide power devices in new energy vehicles, photovoltaic energy storage and other industries, the silicon carbide epitaxial market is also expanding rapidly. Industry Research data show that the global silicon carbide epitaxial market size is 172 billion US dollars in 2020, and it is expected to reach 1.233 billion US dollars by 2027. The compound annual growth rate of 32.5%, the market research company Y0LE and TECHCET released silicon carbide wafer materials report shows that the global equivalent 6-inch silicon carbide epitaxial wafer market size is expected to reach about 800,000 (YOLE) and 1,072 million (TECHCET) in 2023.
From a value point of view, the added value of the silicon carbide industry chain is concentrated upstream, and the epitaxial (including substrate) has a higher value in the silicon carbide industry chain.
According to CASA data, substrate and epitaxy, as the upstream link of the silicon carbide industry chain, account for 47% and 23% of the cost structure of silicon carbide power devices, respectively. High production barriers to high-quality silicon carbide epitaxial sheets, coupled with strong downstream demand for global silicon carbide devices, resulting in a tight supply of high-quality silicon carbide epitaxial sheets, making the value of silicon carbide epitaxial sheets in the industrial chain is relatively high.
From the point of view of importance, silicon carbide crystal in the growth process will inevitably produce defects, the introduction of impurities, resulting in the quality and performance of the substrate material are not good enough, and the growth of the epitaxial layer can eliminate some defects in the substrate, so that the lattice is arranged neatly. Now almost all devices are realized on the epitaxy, so the epitaxy quality has a decisive impact on the performance of the device, and the epitaxy quality is affected by the crystal and substrate processing, epitaxy is in the middle of an industry, plays a key role.
On the one hand, the quality of silicon carbide epitaxial sheet is affected by the thickness and doping concentration of the key parameters. The epitaxial parameter requirements depend on the design of the device, and the epitaxial parameters are different according to the voltage level of the device. The greater the external thickness (the greater the difficulty), the higher the voltage can withstand, generally 100V voltage needs 1μm thickness epitaxy, 600V needs 6μm, 1200-1700V needs 10-15μm, 15000V needs hundreds of microns (about 150μm).
On the other hand, the control of SIC epitaxial defects is the key to the fabrication of high-performance devices, and defects will seriously affect the performance and reliability of SIC power devices. The epitaxial defects mainly include: substrate defects, such as microtubule, penetrating screw dislocation TSD, penetrating edge dislocation TED, base plane dislocation BPD, etc. Dislocation caused by epitaxial growth; Macro defects, such as triangle defects, carrot defects/comet defects, shallow pits, growing stacking faults, falling objects, etc. TSD and TED basically do not affect the performance of the final silicon carbide device, while BPD will lead to the degradation of device performance. Once macroscopic defects appear on the device, the device will fail to test, resulting in lower yield.
At present, the preparation methods of SiC epitaxy mainly include: chemical vapor deposition (CVD), molecular epitaxy (MBE), liquid phase epitaxy (LPE), pulsed laser deposition and sublimation (PLD).
Compared with the three preparation methods, although the epitaxy quality of silicon carbide prepared by MBE method and LPE method is better, the growth rate is too slow to meet the needs of industrialization, and CVD growth rate is higher, epitaxy quality is also in line with the requirements, and the CVD system is relatively simple and easy to operate, and the cost is lower. Chemical vapor deposition (CVD) is the most popular 4H-SiC epitaxy method at present. Its advantage is that the gas source flow, reaction chamber temperature and pressure can be effectively controlled during the growth process, which greatly reduces the epitaxial CVD process.
Summary: With the improvement of the voltage level of the device, the epitaxial thickness has developed from a few microns in the past to tens or even hundreds of microns. Domestic enterprises have gradually increased the amount of 6-inch silicon carbide epitaxy growth, and began to extend to the research and development and production of 8-inch epitaxy, but there is no large-scale supply capacity. In the field of low and medium pressure, domestic silicon carbide epitaxy can basically meet the demand, and it is very scarce in the field of high pressure. Compared with the 6-inch, 8-inch silicon carbide epitaxial edge loss is smaller, the available area is larger, and can increase production capacity, and the cost is expected to be reduced by more than 60% in the future through the improvement of production and economies of scale.
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