Raw material processing of monocrystalline silicon

Polycrystalline silicon - zone melting, Czochralski - monocrystalline silicon, you are doing it :(?

I am a fresh graduate applying for a raw material position and would like to know some information in advance. Please feel free to enlighten me! ! !

Polycrystalline silicon is a form of elemental silicon. When molten elemental silicon solidifies under supercooling conditions, silicon atoms are arranged in the form of a diamond lattice into many crystal nuclei. If these crystal nuclei grow into crystal grains with different crystal plane orientations, these crystal grains combine to form polycrystalline silicon. Polycrystalline silicon can be used as raw material for pulling single crystal silicon. The difference between polycrystalline silicon and single crystal silicon is mainly reflected in the physical properties. For example, the anisotropy of mechanical properties, optical properties and thermal properties is far less obvious than that of single crystal silicon. ； In terms of electrical properties, the conductivity of polycrystalline silicon crystals is far less significant than that of single crystal silicon, and may even have almost no conductivity. In terms of chemical activity, the difference between the two is minimal. Polycrystalline silicon and monocrystalline silicon can be distinguished by their appearance, but the real identification requires analysis to determine the crystal plane direction, conductivity type and resistivity of the crystal. 　　1. Overview of the International Polysilicon Industry Currently, crystalline silicon materials (including polycrystalline silicon and monocrystalline silicon) are the most important photovoltaic materials, with a market share of more than 90%, and will remain the mainstream material for solar cells for a long time to come. The production technology of polycrystalline silicon materials has long been mastered in three countries: the United States, Japan and Germany. * * In the hands of 10 factories of 7 companies, a situation of technological blockade and market monopoly was formed. 　　The demand for polysilicon mainly comes from semiconductors and solar cells. According to different purity requirements, it is divided into electronic grade and solar grade. Among them, electronic-grade polysilicon accounts for about 55%, and solar-grade polysilicon accounts for 45%. With the rapid development of the photovoltaic industry, the demand for polysilicon for solar cells is growing faster than the development of semiconductor polysilicon. It is expected that by 2008, the demand for solar polysilicon will exceed electronic-grade polysilicon. 　 　　In 1994, the total output of solar cells in the world was only 69MW, while in 2004 it was close to 1,200MW, an increase of 17 times in just 10 years. Experts predict that the solar photovoltaic industry will surpass nuclear power and become one of the most important basic energy sources in the first half of the 21st century. The output and composition ratio of solar cells in various countries around the world are shown in Table 1. 　　It is reported that the US Department of Energy plans to have a cumulative installed capacity of 4,600MW by 2010, Japan plans to reach 5,000MW in 2010, and the European Union plans to reach 6,900MW. It is expected that the world's cumulative installed capacity in 2010 will be at least 18,000MW. 　　From the above speculation analysis, the polysilicon used in solar cells will be at least 30,000 tons by 2010. Table 2 gives the prediction of the world's solar polysilicon process. According to foreign data analysis reports, the world's polysilicon production in 2005 was 28,750 tons, of which semiconductor grade was 20,250 tons and solar grade was 8,500 tons. Semiconductor grade demand was approximately 19,000 tons, with a slight surplus. ； The demand for solar-grade polysilicon is 15,000 tons, which is in short supply. Since 2006, there has been a gap in demand for both solar-grade and semiconductor-grade polysilicon, among which the gap in solar-grade production capacity is even greater. 　　According to Japan's Rare Metal Impurities report on November 24, 2005, the world's semiconductor and solar polysilicon demand is tight, mainly due to the rapid expansion of the solar energy market centered in Europe. It is expected that in 2006, In 2007, the unbalanced supply of polysilicon will become more and more serious. The original difference between semiconductor grade and solar grade in terms of polysilicon price will gradually reduce or even eliminate. In 2005, the world's solar cell output was about 1GW. If 1MW of polysilicon is used 1 Calculating 2 tons, a total of 12,000 tons of polysilicon is needed. The average annual growth rate of world solar cells from 2005 to 2010 is 25%. By 2010, the total annual demand for polysilicon used in semiconductor solar cells around the world will exceed 63,000 tons. 　　The world's major polysilicon manufacturers include Japan's Tokuyama, Mitsubishi, and Sumitomo, the United States' Hemlock, Asimi, SGS, and MEMC, and Germany's Wacker. Most of their annual production capacities are more than 1,000 tons. Among them, Tokuyama, Hemlock, and Wacker have the largest production scale, with annual production capacities of 3,000-5,000 tons. 　　The main technical characteristics of international polysilicon are as follows:: 　　(1) Multiple production process routes coexist, and the situation of industrialized technology blockade and monopoly will not change. Since the main and auxiliary raw materials used in each polysilicon production plant are different, the production process technology is different. ； Furthermore, there are also differences in the corresponding technical and economic indicators, product quality indicators, uses, product testing methods, process safety, etc. of polysilicon products. Each has its own technical characteristics and technical secrets. In general, the main traditional processes for polysilicon production in the world are: Improved Siemens method, silane method and fluidized bed method. Among them, the polysilicon production capacity produced by the improved Siemens process accounts for about 80% of the world's total production capacity. The situation of industrialized technology monopoly and blockade will not change in the short term. 　　(2) Research on new generation low-cost polysilicon process technology is unprecedentedly active. In addition to traditional processes (electronic grade and solar grade compatible) and technology upgrades, several new process technologies have emerged specifically for the production of solar grade polysilicon, mainly including: Low-priced technology that improves the Siemens method ； Metallurgical extraction of high-purity silicon from metallic silicon ； High purity SiO2 is directly produced ； Melt precipitation method (VLD: Vaper to liquid deposition） ； Reduction or thermal decomposition process ； Chlorine-free process technology, low-temperature preparation of solar-grade silicon from Al-Si solution ； Molten salt electrolysis method, etc. 　　2. Overview of the domestic polysilicon industry: the growth of my country’s integrated circuits, the development of silicon wafer production and solar cell industries, * * Drive the growth of polysilicon materials. 　 　　Polycrystalline silicon for solar cells is calculated based on the requirement of 11-12 tons of polycrystalline silicon per 1MW of polycrystalline silicon solar cells. In 2004, my country's polycrystalline and monocrystalline solar cell output was 48.45MW, and the polycrystalline silicon consumption was about 678 tons. However, the actual production capacity has reached about 70MW, and the polycrystalline silicon gap has reached more than 250 tons. 　　By the end of 2005, the domestic solar cell production capacity will reach 300MW, and the actual output will be about 110MW, which will require about 1,400 tons of polysilicon. It is predicted that by 2010, the solar cell output will reach 300MW, which will require a conservative estimate of about 4,200 tons of polysilicon. Therefore, the production of solar cells will * * Driven by the increase in demand for polysilicon, see Table 3. 　　In 2005, the operating rate of China's monocrystalline silicon companies for solar cells was between 20% and 30%, and the operating rate of monocrystalline silicon companies for semiconductors was between 80% and 90%. Neither of them could produce at full capacity, mainly due to insufficient supply of polycrystalline silicon. It is expected that the expanded output of polysilicon manufacturers will still not be able to meet the needs of rapid growth. 　　In 2005, the global supply of polysilicon for solar cells was approximately 10,448 tons, while the demand for silicon materials for solar cells in 2005 was approximately 22,881 tons. If the demand for polysilicon for solar cells accounts for 65% of the total demand, the demand for polysilicon for solar cells would be approximately 14,873 tons, resulting in a global market gap of 4,424 tons for polysilicon for solar cells. In 2005, there was a shortage of 6,000 tons of polysilicon for semiconductors, and a shortage of 4,424 tons of polysilicon for solar energy, totaling 10,424 tons. The supply was severely insufficient, causing global polysilicon prices to rise. The current polysilicon market continues to heat up, causing various manufacturers to list production expansion plans. According to statistics from the International Photovoltaic Organization, global polysilicon production capacity will reach 49,550 tons by 2008, and will reach 58,800 tons by 2010. It is estimated that global polysilicon demand will reach 85,000 tons by 2010, leaving a gap of 26,200 tons. In the long run, considering the future shortage of petrochemical energy and the strong support of various countries for the solar industry, demand will continue to grow. According to the European Photovoltaic Industry Federation's 2010 photovoltaic industry development plan for various countries, global photovoltaic production will reach 15GW (1GW = 1000MW) by then. It is assumed that 60% of them will use polysilicon as raw materials. If technological progress consumes 10 tons of polysilicon per MW, it is conservatively estimated that the world will need at least 50,000 tons of solar polysilicon. 　　my country's polysilicon industry started in the mid-1950s and 1960s, with more than 20 production plants. Due to the difficulty of production technology, small production scale, backward process technology, serious environmental pollution, high energy consumption, and high costs, most companies lost money and stopped production or changed production. By 1996, only four companies remained, namely Emei Semiconductor Materials Factory (Institute), Luoyang Monocrystalline Silicon Factory, Tianyuan Chemical Factory and Lenggang Industrial Company, with a total output of 102.2 in that year. tons, and there is a big gap between production capacity and production technology compared with foreign countries. 　　After 1995, Lengguang Industrial Company and Chongqing Tianyuan Chemical Plant ceased production one after another. At present, the main domestic polysilicon manufacturers include Luoyang China Silicon High-tech Company, Sichuan Emei Semiconductor Factory and Sichuan Xinguang Silicon Industry Company. By the end of 2005, Luoyang China Silicon High-tech Company's 300-ton production line has been officially put into operation, and the second-phase expansion of the 1,000-ton polysilicon production line has also broken ground. Henan Province plans to expand it to 3,000 tons and build the largest silicon industry base in the country. Sichuan Emei Semiconductor Materials Factory (Institute) is the first enterprise in China to possess polysilicon production technology. In 2005, solar cell users invested, and the expanded 220-ton polysilicon production line will be put into operation in the first half of 2006. Sichuan Xinguang Silicon Industry Company implemented 1 The construction of a 000-ton polysilicon production line is accelerating and is planned to be put into operation by the end of 2006. In addition, Yunnan, Yangzhou, Shanghai, Heihe, Jinzhou, Qinghai, Inner Mongolia, Yichang, Guangxi, Chongqing, Liaoning, Handan, Baoding, Zhejiang and other places also have plans to build production lines. 　　3. Main issues in industry development Compared with the international advanced level, the gap in industrialization among domestic polysilicon manufacturers is mainly reflected in the following aspects:: 　　1. Low production capacity and prominent contradiction between supply and demand. In 2005, the operating rate of China's monocrystalline silicon companies for solar energy was between 20% and 30%, and that of monocrystalline silicon companies for semiconductors was between 80% and 90%, unable to achieve full capacity production. Polycrystalline silicon technology and market are still firmly controlled by a few manufacturers in the United States, Japan, and Germany, which seriously restricts the development of my country's industry. 2. The production scale is small. The currently recognized minimum economic scale is 1,000 tons/year, and the optimal economic scale is 2,500 tons/year. However, my country's current polysilicon production enterprises are still far away from this scale. 3. The process equipment is backward, similar products consume too much material and electricity, and there are many problems with three wastes. Compared with international levels, the energy consumption of domestic polysilicon production is more than twice as high, and product costs lack competitiveness. 4. The reliability, advancement, maturity and mutual compatibility of each subsystem of the kiloton-level process and equipment technology need to be verified by production operations, and further improvement and improvement are needed. 5. Domestic polysilicon production enterprises have weak technological innovation capabilities and too little investment in basic research funds. In particular, the R&D and manufacturing capabilities of non-standard equipment are poor. 6. Place * * There are hidden concerns about low-level duplication of construction when investing in polysilicon projects with corporate projects. 4. Countermeasures and suggestions for industry development 1. The market conditions for developing and expanding my country’s polysilicon industry are basically in place and the time is ripe. * * Relevant departments have increased their support for polysilicon industry technology research and development, technological innovation, process improvement, and project construction, and seized favorable opportunities to develop and expand my country's polysilicon industry. 2. Support the implementation of the most qualified improved Siemens method common technology, accelerate the breakthrough of key technologies for the industrialization of kiloton-level polysilicon, and form a polysilicon industrial production line from material production technology, equipment, automatic control, recycling and recycling, and the material performance is close to the international similar product indicators ； Establish an energy-saving, low-consumption, environmentally friendly, recycling and economical polysilicon material production system to improve the international competitiveness of our polysilicon. 3. Rely on universities and research institutes to strengthen basic and forward-looking research on new generation low-cost process technology, establish a knowledge and technology innovation system for low-cost solar energy and polysilicon research and development, and obtain production processes and technologies with independent intellectual property rights. 4. * * The competent authorities shall strengthen macro-control and industry management to avoid duplication of investment and construction of low-level projects and ensure the orderly and sustainable development of the industry.

Monocrystalline silicon production is a purification process. The raw material is industrial silicon, which is more than 90% silicon.