Polysilicon/Silicon Crystal Technical Information

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Polysilicon/silicon crystal technical data: Silicon of solar-grade is used in the solar industry. The \"International Energy Outlook 2006\" published by the Information Management Office of the U.S. Department of Energy predicts that by 2030, global electricity consumption will be twice that of 2003. Global electricity use is expected to rise from 14,781 billion kWh in 2003 to 30,116 billion kWh by 2030, representing an average annual growth rate of 2.7%. The large-scale development and utilization of renewable energy has become an important part of the energy strategies of countries in the future. Looking at the global trends in the utilization and development of renewable energy, wind energy, solar energy, and biomass energy are growing the fastest and have the best industrial prospects, with their rates of development far exceeding those of conventional energy sources. Based on the current situation, a rough estimate of the world’s potential renewable energy resources is as follows: hydroelectric energy resources amount to 4.6 Tw, with 0.9 Tw being exploitable resources ； 　　Developable wind energy resources: 2TW ； 　　Bioenergy 3Tw ； 　　The solar energy resource is 120,000 TW, with the actually exploitable resource amounting to as much as 600 TW. 　　There are various ways to utilize solar energy, but only large-scale solar power generation can truly serve as a supplementary energy source for humanity in the future and form the basis of the future energy structure. 　　In our country, the solar energy that reaches the Taklamakan Desert each year alone, calculated based on a photovoltaic conversion efficiency of 20%, represents an amount of energy that can be extracted amounting to 122760 billion kilowatt-hours. This is equivalent to the power generation capacity of 1,500 Three Gorges power stations (the annual power generation of the Three Gorges stations once all are in operation is 84.7 billion kWh). It is 50 times the national power generation in 2005 (2474.7 billion kWh), 43 times the national power generation in 2006 (2834.4 billion kWh), and 37 times the national power generation in 2007 (3255.9 billion kWh). 　　Silicon of electronic grade can be used in the electronics industry, and the production volume of electronic-grade silicon materials is an indicator of the development level of the electronics industry; it also holds **strategic significance**. However, the development of electronic-grade silicon should come after that of solar-grade silicon; let’s not discuss electronic-grade silicon for now. 　　Given the immense potential of solar energy, it seems only right to invest some funds to further develop theories of sustainable development in order to support the production of silicon materials and bring benefits to the general public. However, this is not the case. According to the **Medium- and Long-Term Development Plan for Renewable Energy**, by 2020, the target for wind power capacity is 30 million kilowatts, biomass power generation is to reach 30 million kilowatts, and solar power capacity is set at 1.8 million kilowatts. ”What does this mean? The output of solar cells in China alone in 2007 was enough to meet more than two-thirds of the country’s needs for the next decade or so. In short, the environment for the development of silicon materials is very poor. 　　Why is an industry that should be regarded as a treasure being neglected? Ultimately, it is due to backward technology. Due to technical limitations, the production cost of silicon materials is high, and by-products are difficult to handle. In particular, the hydrogenation of silicon tetrachloride has become a bottleneck in the development of the silicon materials industry. If these key technologies are not resolved, it will be very difficult for the silicon industry to develop in a truly healthy manner. Fortunately, I found a lot of information on the key technologies of silicon materials. To prove that I have indeed found the relevant technology, it is very necessary to give one or two examples. “\"To catch the thief, first capture his leader; to shoot at a man, first shoot at his horse.\" If the biggest challenge in the development of the silicon industry, namely the so-called bottleneck issue of silicon tetrachloride hydrogenation, can be resolved, I think it will be very convincing. To explain the main reasons why the hydrogenation of silicon tetrachloride is difficult to achieve at present, it is necessary to compare it with the current status of silicon tetrachloride hydrogenation technology in our country; I hope no one will object. Please take a look at the following document: **“Guidelines for Applying for Key Projects under the Science and Technology Support Program: Development of Key Technologies for the Polysilicon Materials Industry”** I. Guidelines Polysilicon is a key raw material used in integrated circuits and photovoltaic power generation, and it constitutes an important part of the priority themes related to basic raw materials in the manufacturing sector as outlined in the **Medium- and Long-Term Science and Technology Development Plan”. This project focuses on the industrialization engineering technology for the improved Siemens process under the most favorable conditions, aiming to overcome and enhance key production technologies. It provides a comprehensive set of technical solutions for polysilicon production lines with a capacity of thousands of tons. The product quality produced by such lines meets the requirements for manufacturing 8-inch silicon single crystals, and the production costs are competitive compared to those of global polysilicon manufacturers. Keep track of the global trends in new technology research and develop new low-cost polysilicon production processes with independent intellectual property rights. 　　This project includes six research topics: II. Guidelines Topic 1: Research on the synthesis and purification processes sowie key equipment for large-scale production of trichlorosilane Funding source: **2 million yuan allocated. 　　Project 2: Research on High-Efficiency Pressurized Reduction Furnace Systems Funding source: **3.3 million yuan allocated. 　　Project 3: Large-scale improved Siemens process for exhaust gas recovery technology and equipment Funding source: **2.3 million yuan allocated. 　　Topic 4: Research on Large-Scale Hydrogenation Technology and Equipment for Silicon Tetrachloride 1. Main research contents: Hydrogenation at high temperature and low pressure ； Low-temperature pressurized hydrogenation. 　　2. Key evaluation indicators Key evaluation indicators for high-temperature and low-pressure hydrogenation: (1) The silicon tetrachloride processing capacity per hydrogenation furnace > 540 kg/h ； The primary conversion rate of silicon tetrachloride in the furnace is >20%. 　　(2) Power consumption: 70 kwh/kg•Si. 　　(3) The system operates continuously and stably. 　　Key performance indicators for low-temperature pressurized hydrogenation: (1) The silicon tetrachloride processing capacity of each hydrogenation furnace > 5000 kg/h ； The primary conversion rate of silicon tetrachloride in the furnace > 25%. 　　(2) Power consumption: 35 kwh/kg•Si. 　　(3) The system operates continuously and stably. 　　3. Implementation period: 3 years 　　4. Funding source: **Grant of 6 million yuan. 　　Project 5: Research on New Low-Cost Polysilicon Production Technologies Funding source: **4 million yuan allocated. 　　Topic 6: Standardization, Patent System Construction, and Research on Polysilicon Funding source: **2.4 million yuan allocated. 　　Judging from the amount of funding allocated, silicon tetrachloride hydrogenation is indeed the most important issue. Next, let’s take a look at the technical documentation on silicon tetrachloride hydrogenation technology. 　　Overcoming the development bottlenecks in the silicon industry——Silicon tetrachloride hydrogenation technology I. This technology involves the hydrogenation of silicon tetrachloride under high-pressure plasma conditions, particularly the hydrogenation reaction of silicon tetrachloride using boron as a catalyst. 　　Currently, the process used in the semiconductor industry to produce silicon involves reacting trichlorosilane with hydrogen; during this process, trichlorosilane is consumed, and polycrystalline silicon is deposited on a heated substrate. In the reaction, most of the trichlorosilane is not converted into silicon, but rather into silicon tetrachloride. Although silicon is an effective reaction product, silicon tetrachloride is a low-value and practically useless byproduct of the reaction. The low conversion rate of silicon increases the cost of producing it. One way to reduce the overall cost of producing silicon is to recycle silicon tetrachloride and convert it into reactants that can produce silicon. 　　The reaction equation for the conversion of silicon tetrachloride into more valuable silicon-producing compounds under high-pressure plasma conditions is as follows: HPP + H2 + SiCl4 → SiHC3 + SiH2Cl2 + HCl. In this reaction, the efficiency of hydrogenating (converting) silicon tetrachloride depends primarily on the H2/SiCl4 ratio of the input gases and the power of the RF power supply used in HPP. Increasing the H2/SiCl4 ratio of the inlet gas in the reactor can increase the conversion rate of SiCl4. The highest H2/SiCl4 ratio results in the highest conversion rate of SiCl4, and this highest ratio is determined by the proportion of SiH2Cl2 in the polysilane polymer after the reaction. This polymer is an oily, impact-sensitive, and hazardous substance, and its use should be justified from a safety perspective. Even small amounts of polymers should be avoided, as they can deposit on the inner walls of the reactor, and over time this accumulation can reach dangerous levels. 　　For a given feed rate of SiCl4 and a certain H2/SiCl4 ratio, an increase in conversion rate is inherently related to an increase in the power of the radio frequency power supply; when the conversion rate reaches its maximum value, it decreases as the power of the radio frequency power supply increases. For the unique high-pressure plasma reactor system, the H2/SiCl4 ratio is 4.2, the power of the RF power supply is 1.7 KW, and the feeding rate of silicon tetrachloride is 10.7 gm/min (as stated in the original text; could it be mg/min, g/min, Kg/min, or some other unit?) ), the conversion rate can reach 49.9% with no significant polymer form. At the outlet of the HPP reactor, the reaction products were found to contain 50.1% SiCl4, 41.3% SiHCl3, and 8.6% SiH2Cl2. A conversion rate of 49.9% is very high, and it has a highly valuable impact compared to the alternative technologies. Although this technology boasts a very high conversion rate, it is still necessary to further improve this rate, reduce the power requirements of the RF power supply, and increase the reactor’s capacity to hold SiH2Cl2. Of course, this technology provides a way to use a catalyst to increase the conversion rate of SiCl4. 　　The goal of this technology is to increase the amount of SiHCl3 produced upon the hydrogenation of SiCl4. 　　Technical Overview The other objectives and advantages mentioned above can be achieved through a catalytic HPP hydrogenation reactor. Hydrogen and silicon tetrachloride react under HPP conditions in the presence of boron or aluminum to produce SiHCl3 and SiH2Cl2. The catalyst boron can exist in the form of B2H6 (diborane) or BCl3 (boron trichloride), while the catalyst aluminum can exist in the form of AlCl3 (aluminum trichloride). 　　Image description: The only image is an illustrative diagram of the HPP device of this technology. 　　 　　Detailed explanation: The only image is a schematic diagram of the hydrogenation process equipment. The deposition device means generating high-pressure RF plasma. High-pressure plasma (HPP) means that plasma is generated at a pressure greater than 100 atmospheres (approximately 13.3 KP), preferably at 1 atmosphere pressure. The hydrogenation apparatus includes a radio frequency generator 10 and an impedance matching module 12; an example of an impedance matching module is a hollow coil inductor that allows the reaction gas to pass through. When the impedance matching module is adjusted appropriately, a high voltage is generated at its output terminal. This high voltage can generate plasma and is connected to the high-voltage plasma nozzle 14. The reactants react under high voltage after passing through the coil and nozzle. The high-pressure plasma nozzle is located within the reaction chamber 16, and the surroundings of the reaction chamber 16 can be controlled. Both ends of the reaction chamber 16 are sealed by covers 18. The reactants in this technique include tetrachlorosilane 20, hydrogen 22, a catalyst such as boron 24, an inert gas such as helium 26, all of which are connected to a gas control system 28. The gas control system can control and meter each type of reactant gas. The gas control system provides the impedance matching module with a mixture of gases in the appropriate proportion, and then the gas passes through the HPP nozzle 14. In the practice of this technology, an inert gas such as helium is introduced first, followed by hydrogen, while high-pressure plasma is generated. After plasma is generated, the impedance matching module is adjusted appropriately, and silicon tetrachloride along with catalysts of boron or aluminum are added to the plasma vapor. The best catalyst is boron, in the form of B2H6 or BCl3. The flowing substances are collected in 30, and then separated, purified, and the catalyst is removed, etc. 　　The following non-exhaustive examples represent the best manifestations of this technology and can further illustrate it. 　　Example 1: In the silicon tetrachloride hydrogenation reaction shown in the figure, the feed rate of silicon tetrachloride is maintained at 12 gm/min, the power of the radio frequency source is set to 1.3 KW, and the feed rate of hydrogen changes in accordance with the feed rate of silicon tetrachloride. Do not add B2H6 to the flowing gas during the experiment. The flow rate of B2H6 gas is measured in parts per million (ppm). The products flowing out of the reactor were collected and analyzed by gas chromatography (GC). The experimental results are shown in Table 1. 　　Table 1 shows the effect of adding trace amounts of B2H6 as the H2/SiCl4 ratio changes. Each example shows that the conversion rate of SiCl4 increases upon the addition of catalyst B2H6. Furthermore, B2H6 also increased the conversion rate of SiCl4 to SiH2Cl2; with B2H6 concentrations of 10.1 and 6.4 ppm in terms of H2/SiCl4 ratio, the proportion of SiH2Cl2 in the collected product exceeded 25%. No polymeric form was observed in B2H6 with H2/SiCl4 ratios of 10.1 and 6.4 ppm. However, under analogous conditions, no considerable polymers of B2H6 could be observed. In the presence of B2H6, polymers can be observed when the H2/SiCl4 ratio is greater than 6. Mass spectrometric analysis of the gases collected from the HPP reactor showed that B2H6 is converted to BCl3 in the plasma. 　　Example 2: In the silicon tetrachloride hydrogenation reaction shown in the figure, the H2/SiCl4 ratio is 5.19, the power of the radio frequency power supply is 1.5 KW, and the feed rate of silicon tetrachloride is maintained at 12 gm/min. The concentration of B2H6 added to the reactor varies, and Table 2 shows the reaction results for adding B2H6 at different concentrations. 　　Table 2 shows the addition of boron at a series of concentrations (5 ppm to 15 ppm). The concentration of catalytically active boron has no significant effect on the hydrogenation of silicon tetrachloride. In further experiments, with the boron concentration ranging from 0.1 ppm to 35 ppm, the results showed that a lower concentration of boron is more suitable. 　　Although this technology is not intended to be constrained by any theory, boron can serve as a catalyst in the following ways: a) it increases the conversion rate of SiH2Cl2, b) it eliminates the formation of polymers. A trace amount of catalyst can be used to remove polymers at high H2/SiCl4 ratios, which increases the ratio of SiH2Cl2 in the gas collected from the HPP reactor and improves the conversion rate of SiCl4. At the same time, the catalyst reduces the power requirement of the RF power supply during the hydrogenation of SiCl4. 　　Solving the bottlenecks in the development of the silicon materials industry——Silicon tetrachloride hydrogenation technology II. Trichlorosilane is abbreviated as TCS, while silicon tetrachloride is abbreviated as STC. 　　Some details regarding the process: An industrial production process in which silicon tetrachloride (STC) reacts with silicon and hydrogen to produce trichlorosilane (TCS); the silicon used is of metallurgical grade, and the reaction vessels are fluidized bed reactors, solid bed reactors, or stirred bed reactors. The process temperature is between 400 and 600 degrees Celsius. 　　Reaction equation: Si + 3SiCl4 + 2H2 = 4HSiCl3. TCS can also be produced by reacting metallurgical silicon with HCl. The process temperature is between 250 and 1100 degrees Celsius. Different temperatures affect the conversion rate of TCS, and the content of TCS after the reaction ranges from 10 to 85%. Reaction equations:
Si + 3HCI = HSiCI3 + H2
Si + 4HCI = SiCI4 + 2 H2
During the production of polysilicon, TCS decomposes to produce a large amount of STC and a certain amount of silane. 　　4HSiCI3 = Si + 3SiCI4 + 2H2 　　4HSiCl3 = SiH4 + 3SiCl4 　　The main method of processing STC is to react it with hydrogen and oxygen to produce silicon dioxide (white carbon black); some of this product is used in the production of optical fibers, while the rest is sold for use in other applications. Generally speaking, there are too many STCs available on the market, so it is necessary to recycle a portion of them in order to balance the production volume of STCs. 　　The advantage of using STC to react with metallurgical silicon and hydrogen to produce TCS is that it allows for the recycling of STC, a by-product from the polysilicon production process. Polysilicon is produced by converting TCS derived from silicon; therefore, recycling STC can reduce the demand for silicon. Only a portion of the STC in the reactor can be converted into TCS, and the maximum conversion rate of STC is determined by the equilibrium state of the reaction. The complete conversion of STC requires multiple reactors, followed by the distillation of TCS. Under normal conditions, the conversion rate in a reactor is lower than that at equilibrium, which is determined by the kinetic properties influenced primarily by temperature. Adding a catalyst can increase the conversion rate (at **equilibrium**). Common catalysts used in this process are copper (any copper-based material will work) and iron (any iron-based material will work); metallurgical silicon contains iron, which increases the conversion rate in the reaction. 　　Raising the temperature reduces the conversion rate, while increasing the pressure increases it. Figures 1 and 2 show the functional relationship between conversion at equilibrium and temperature and pressure. 　　The impurity elements present in metallurgical silicon include iron, calcium, aluminum, manganese, nickel, zirconium, oxygen, carbon, zinc, titanium, boron, phosphorus, and other elements. Some elements in the reaction form inert compounds; for example, iron and calcium can form stable chlorides. Depending on their particle size, some metal chlorides are blown out of the reactor by silane gas, while others form clumps within the reactor. Other impurity elements such as aluminum, zinc, titanium, boron, and phosphorus typically leave the reactor as volatile metal chlorides along with silanes. 　　O and C do not react or react very slowly in the reactor, and oxygen- and carbon-containing compounds accumulate there to form slag. The smallest slag particles are blown out of the reactor and remain in the filtration system. 　　Many elements in metallurgical silicon affect the properties of silicon during the reaction of silicon, hydrogen, and STC to produce TCS. 　　Contents of the process: It has been previously found that adding a certain amount of manganese to the reactor is used in the production of STC. During the reaction between silicon, STC, and hydrogen, the total amount of manganese present in the reactor has a significant impact on the conversion rate of TCS formation. 　　In this process, the manganese content in the metallurgical silicon added to the reactor does not exceed 50 ppmw; the reaction temperature ranges from 400 to 800 degrees Celsius, and the reaction pressure ranges from 0.1 to 30 atmospheres. 　　Analysis showed that a silicon-manganese content of 50 ppmw or less when added to the reactor can result in a high conversion rate, with a manganese content of 35 ppmw being optimal. 　　As the reaction proceeds, the added silicon is consumed, and the manganese content increases. The total manganese content in the reactor should not exceed 200 ppmw, and it is preferable not to exceed 150 ppmw. The control of manganese content in metallurgical silicon is achieved by using raw materials with low manganese content, as well as electrodes, electrode pastes, and electrode casings that also have low manganese levels. To further reduce the manganese content in silicon, filtration can be performed after the silicon has solidified; suitable solutions include HF, HCl, and/or FeCl3. 　　 　　Brief description of the graphs: Figures 1 and 2 show the theoretical conversion curves of STC (based on equilibrium conditions). 　　Figures 3 to 6 show the conversion curves of STC in a fluidized bed reactor, depicting the first conversion through the first reactor. 　　Detailed description: Examples 1 to 4 all depict continuous experimental fluidized bed reactors made of carbon steel with a heated copper block embedded in them. The temperature and pressure in the experiment were maintained at 550 °C and 4 bar, respectively. For each test, 5 grams of silicon particles with a particle size of 125 to 180 μm were added to the reactor. 5 grams of silicon should always be maintained in the reactor, and more silicon can be added continuously to replace that which has reacted. 0.08 grams of CuCl (equivalent to 1% copper) together with the 5 grams of silicon added in the first instance were added to the reactor. The mixed gas fed into the reactor consists of normal hydrogen at 335 milliliters per minute, silicon tetrachloride at 168 milliliters per minute (69 grams per hour), and argon at 56 milliliters per minute. The gas mixture composed mainly of TCS and STC exiting the reactor is analyzed using a gas chromatograph (GC). Argon is an internal standard used in gas chromatography analysis. The sample measured is the conversion rate of STC from the first reactor. 　　Example 1: The synthetic silicon samples were composed of high-purity silicon mixed with 0.21% iron, 0.12% Al, and 25, 50, and 200 ppmw of manganese (samples A, B, and C); after grinding in an induction furnace, their particle sizes ranged between 125 and 180 μm. Sample D was made from silicon with a very low manganese content of 1 ppmw. Table 1 shows the chemical compositions of samples A, B, C, and D. 　　Samples A, B, C, and D were used in a continuous experimental fluidized-bed reactor at 550 degrees Celsius to produce silicon trichloride. Figure 3 shows the conversion rate of STC in samples A, B, C, and D. 　　As can be seen from Figure 3, the conversion rate of STC increases as the manganese content decreases. Samples A, B, and D have very high conversion rates. 　　Example 2: Silicon produced by Elkem AS, Bremanger Smelteverk, containing 5 ppmw of manganese; silicon particles with sizes ranging from 125 to 180 μm were obtained through grinding and sorting (Sample E). When about 25% of the initially added silicon has been consumed, 50 milligrams (1%, by weight) of manganese powder is added to the reactor. 　　Table 2 shows the chemical composition analysis of samples E, F, G, H, and I. 　　Figure 4 shows the conversion rates of STC without manganese addition and with manganese addition. 　　As can be seen from Figure 4, the STC conversion rate decreased by more than 75% after adding 1% by weight of manganese powder. This clearly shows that if the manganese content in the reactor increases, the conversion rate of STC will drop sharply. 　　Example 3: The synthetic silicon sample was made by mixing high-purity silicon with 0.21% iron and 0.12% aluminum; it was ground in an induction furnace, and silicon particles with a size of 125 to 180 μm were selected (Sample D). 　　The chemical composition of Sample D is shown in Table 1. 　　Sample D was used at 550 degrees Celsius in the aforementioned continuous experimental fluidized-bed reactor to produce trichlorosilane. 　　When about 28% of the initially added silicon has been consumed, 10 mg (200 ppmw) of manganese powder is added to the reactor. 　　Figure 5 shows the conversion rate of STC for sample D obtained after adding 200 ppmw of manganese powder. 　　As can be seen from Figure 5, the conversion rate of STC decreased by about 35% after adding 200 ppmw of manganese powder. Therefore, it is very important to maintain a low manganese content in the reactor to achieve a high conversion rate of STC. 　　Example 4: Silica particle samples with particle sizes ranging from 125 to 180 μm were obtained by grinding and screening at different manganese contents (samples E, F, G, H, I). 　　Table 2 shows the chemical composition analysis of samples E to I. 　　Samples E, F, G, H, and I were used to produce trichlorosilane at 550 degrees Celsius in the aforementioned continuous experimental fluidized-bed reactor. Figure 6 shows the conversion rates of STC for samples E to I. 　　As can be seen from Figure 6, the conversion rate of STC decreases as the manganese content increases. The conversion rates of samples E and F are very high. 　　　　Images and tables Images and tables Analysis: 1. The most important technical parameter for the hydrogenation of silicon tetrachloride is the one-time conversion rate. As can be seen from these two technical documents, the one-time conversion rate of silicon tetrachloride hydrogenation abroad is over 50%, which is far higher than the target expected in the research on silicon tetrachloride hydrogenation technology in China. This shows that foreign technology is indeed very advanced. 　　2. Under normal conditions, hydrogen is difficult to react; activating conditions are required to make hydrogen react. The methods for activating hydrogen are not limited to heating; hydrogen can also be activated by turning it into plasma using high voltage before it participates in the reaction. This seems to be able to increase the conversion rate while reducing energy consumption. 　　3. The catalyst is a factor that affects the conversion rate. Catalysts include not only positive catalysts but also negative catalysts. A positive catalyst increases the conversion rate, while a negative catalyst decreases it. In the hydrogenation reaction of silicon tetrachloride, SiCl4 + H2 + Si → SiHCl3, positive catalysts include Cu, Fe, Al, Ni, etc., with their content in Si generally being around 1% ； The countercatalyst is Mn; when the content of Mn in silicon is one part per million, the conversion rate of silicon tetrachloride is over 50%. When the content of Mn in silicon is two parts per ten thousand, the conversion rate of silicon tetrachloride decreases by 35%, and when its content is higher, the conversion rate falls below 10%. In other words, the level of manganese content in silicon has a significant impact on the conversion rate of silicon tetrachloride. Looking back at the requirements in \"Research on Large-Scale Hydrogenation Technology and Equipment for Silicon Tetrachloride\" regarding a \"continuous and stable operation of the system,\" it is evident that the current systems used for the hydrogenation of silicon tetrachloride cannot operate in this manner. The reason for this is likely the increase in Mn content as silicon is consumed, which leads to a decrease in the conversion rate of silicon tetrachloride; in other words, the conversion rate of silicon tetrachloride is unstable. It is a bold speculation, but the lack of appropriate treatment for catalysts in which elements such as Mn affect the conversion rate of SiCl4 is the main reason why silicon tetrachloride hydrogenation technology has difficulty being successfully implemented at present. 　　4. The polysilicon material industry is a knowledge-intensive and capital-intensive industry. Technological intensity is by no means simply the accumulation of knowledge; for example, it is very difficult to achieve success without addressing the technical challenges involved in the hydrogenation of silicon tetrachloride. 　　At present, the technology for producing polysilicon materials in our country is still backward. Due to this backwardness, China’s market has not been opened up; on the other hand, however, many polysilicon companies have emerged, which will surely lead to a competitive landscape among them. In any case, improving technology is the only way forward for the knowledge-intensive silicon materials industry. However, developing technology is not easy, and referring to advanced foreign technical materials can save a lot of time and effort. I have gathered a large amount of technical information on polysilicon/silicon crystals, which might be of some help. The basic information about the materials is as follows: First, the materials consist of technical data on polysilicon/silicon crystals from the United States, Germany, and Japan. 　　Second, the materials mainly relate to the chemical production of polysilicon/silicon crystals. 　　Third, the text of the materials is primarily in the languages of various countries; that is, English for the United States, German for Germany, and Japanese for Japan. 　　Fourth, the data is mainly based on U.S. data. 434 items from the United States, 66 from Japan, 44 from Germany, for a total of 544 items. 　　Fifth, the information is primarily based on the technical data of well-known companies with large polysilicon production capacities. Of this, there are 278 items related to MEMC technology, 66 items related to TOKUYAMA technology, 44 items related to WACKER technology, 21 items related to Hemlock technology, 15 items related to REC technology, and a total of 120 items related to the technologies of other companies. 　　Sixth, the technical documents range in length from around 2,000 words for the shortest ones to 130,000 words for the longest; those related to semiconductor manufacturing are of the longer length, while the two documents on the hydrogenation of silicon tetrachloride are the shortest. 　　Seven, the total size of the data is 1.47 G, and it becomes 1.28 G after compression. 　　Eight, a special reminder: since the information was obtained from abroad, it may contain viruses from foreign sources. Despite being processed by various antivirus programs, it is likely that there are still viruses. Because there have been messages stating that the website refuses access to protect users’ interests. 　　I do have my own views on the prospects of the silicon industry. I believe that solar energy in the future can be described as a “positive cycle”. The so-called positive cycle means that, once solar energy has developed to a certain stage, part of the electricity generated by it is used for the production of more solar energy, while the rest can be utilized for other purposes. For example, the ratio of energy invested to energy produced by solar energy is 1:3. In an era of positive cycles, 1 unit of energy is invested in solar energy, resulting in 3 units of energy being generated. Then, 1 unit of the energy produced by solar energy is used again for solar energy purposes, while the other 2 units are used for other purposes. The 1 unit invested can generate 3 more units of energy, allowing another 1 unit to be invested and 2 units to be used for other purposes. Contrary to the current situation where less energy is used, in an era of positive cycles, more energy will be used. In the era of positive cycles, solar power generation generally exhibits zero or negative costs; there will be no losers in investing in solar energy. People compare madness to installing solar panels in every corner of the Earth where it’s possible to do so. Silicon, which accounts for 26% of the Earth’s composition, is also sufficient to take on this important role. In the era of positive circulation, thanks to the low and rising costs of energy, social productivity will increase significantly, the socio-economic structure will undergo fundamental changes, and people’s quality of life will improve even further. In the era of positive circulation, people will spare no effort in producing hydrogen through water electrolysis for use as various fuels. The energy used in societal activities will come from solar power and end up as pure water, achieving true environmental sustainability without pollution, and thereby leading to a significant improvement in the social environment. The era of positive circulation, just like the information age, has become a characteristic of its own time. All solar energy companies that manage to survive until that era will be remembered as heroes in history. A tribute is paid to all such companies, as well as to those currently involved in the solar energy sector. 　　But prospects are one thing, and investments are another. I am quite optimistic about the prospects of finding relevant information, and I have indeed come across some material, but I’m not sure yet whether good results will be achieved. Moreover, all investments carry risks, so it’s better to be cautious.