III silicon carbide (SiC) - the third generation of semiconductor materials
SiC material as substrate has been applied on a large scale, after epitaxial growth and device manufacturing, it can be made into silicon carbide-based power devices and microwave radio frequency devices. 60%-70% of the cost structure of silicon carbide chips are substrates and epitaxial wafers, of which substrates account for about 40%-50%, which is an important basic material for the development of the third-generation semiconductor industry.
(A) Product categories
As a semiconductor substrate material, silicon carbide wafers can be classified into conductive and semi-insulating types according to their resistivity. Among them, conductive silicon carbide wafers are mainly used in the manufacture of high-temperature and high-voltage power devices, in new energy vehicles, photovoltaic power generation, rail transportation, smart grid, aerospace and other fields of application, the market scale is larger; semi-insulated silicon carbide substrates are mainly used in microwave radio frequency devices and other fields, such as 5G communication, radar, etc., with the accelerated construction of 5G communication network, the market demand is more obvious.
(7) Wafer inspection. Using optical microscope, X-ray diffractometer, atomic force microscope, non-contact resistivity tester, surface flatness tester, surface defects comprehensive tester and other instruments and equipment, test the microtubule density, crystalline quality, surface roughness, resistivity, warpage, curvature, thickness variation, surface scratches and other parameters of silicon carbide wafers, and determine the quality level of the wafer accordingly.
(8) Wafer cleaning. Clean the polished silicon carbide wafers with cleaning chemicals and pure water to remove the polishing solution and other surface stains left on the wafers, and then blow and shake the wafers dry by ultra-high purity nitrogen and shaking dryer; encapsulate the wafers in clean cassettes in the ultra-clean room to form the silicon carbide wafers that can be used immediately downstream.
(C) Key Technologies
The larger the wafer size, the more difficult the crystal growth and processing technology, while the higher the manufacturing efficiency and lower the unit cost of downstream devices. At present, international silicon carbide wafer manufacturers mainly provide 4-inch to 6-inch silicon carbide wafers, CREE, II-VI and other international leading companies have started to invest in the construction of 8-inch silicon carbide wafer production lines. The core key technology points of silicon carbide substrate manufacturing include electronic grade high purity powder synthesis and purification technology, digital simulation technology, single crystal growth technology, single crystal processing (cutting and polishing) technology. It is difficult to improve the formulation of silicon carbide substrate, slow crystal growth, and low yield of finished products.
1.High purity powder
High-purity toner is the basis for growing high-quality SiC crystals, especially for the growth of semi-insulated SiC crystals, which involves preparation technology, synthesis technology and purification technology. Among them, the purification of high-purity toner is extremely demanding in terms of process, while the synthesis involves formulation technology that requires a long time to figure out and accumulate.
2. Digital simulation technology
Digital simulation in silicon carbide crystal fabrication
Single crystal growth temperature at 2350-2500 degrees, because the furnace temperature is not measurable, through high-precision digital simulation technology can save a lot of research and development time and costs, the level of simulation also directly represents the core technology capabilities of single crystal enterprises.
3. Single crystal growth technology
The slow growth of single crystals is an important reason for the high cost of silicon carbide substrates. Currently Cree and domestic mainstream manufacturers are using PVT physical vapor phase transfer method. As the growth rate of silicon carbide crystal is much slower than silicon crystal, 8" silicon wafer can grow to 1-2m in 2-3 days, while silicon carbide 4" wafer can only grow 2-6cm a week. an important factor affecting crystal growth is seed crystal reproduction, seed crystal is the "seed" wafer with the same crystal structure as silicon carbide single crystal, which is the source of crystal growth. The seed crystal is a "seed" wafer with the same crystal structure as the silicon carbide single crystal, which is the source of crystal growth, and the crystal growth is condensed on top of the seed crystal. Seed crystal growth is the core technology of silicon carbide preparation, and it is also one of the core technologies that all silicon carbide substrate companies are judged by.
4.Single crystal processing technology
Due to the very high hardness and brittleness of silicon carbide, grinding, cutting and polishing are time-consuming and have a low yield. Silicon wafer cutting only takes a few hours, while 6" silicon carbide wafer cutting takes hundreds of hours.
(D) domestic substrate prices and trends
The current market 4-inch silicon carbide substrate is relatively mature, high yield, while the price is low, while the price of 6-inch substrate due to the supply of less and low yield into the film, the price is much higher than the 4-inch film. The future to drive the cost of silicon carbide substrates to reduce the three major drivers: process and equipment improvements to speed up the long crystal speed; defect control improvements to improve yields; design improvements to reduce the use of devices using the substrate area.
(E) Global Competition Pattern
The SiC wafer market is currently dominated by the U.S., Europe and Japan, with Chinese companies beginning to emerge. According to Yole forecast, SiC will grow at a CAGR of 31% from 2017 to 2023, reaching a market size of about USD 1.5 billion in 2023. According to the data of the 2020 China Third Generation Semiconductor Silicon Carbide Wafer Industry Analysis Report by Semiconductor Times Industry Data Center, the global semiconductor SiC wafer market in the first half of 2020, the U.S. CREE shipments occupy 45% of the global; European companies are stronger in the field of design and development of SiC devices, with major companies such as Siltronic, STMicroelectronics, IQE, Infineon, etc.. Japan's strong technical force, complete industry chain, the representative companies are Panasonic, Roma, Sumitomo Electric, Mitsubishi, etc., Roma subsidiary SiCrystal occupies 20%, II-VI accounted for 13%; Chinese companies are developing faster, Tianke Heda's market share rose from 3% in 2019 to 5.3% in 2020, Shandong Tianyue accounted for 2.6%.
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