Monocrystalline silicon production process (1)
Monocrystalline silicon is usually produced by first producing polycrystalline silicon or amorphous silicon, and then growing rod-shaped single crystal silicon from the melt by a Czochralski method or a suspension zone melting method. When the molten elemental silicon solidifies, the silicon atoms are arranged in a diamond lattice to form a plurality of crystal nuclei. If the crystal nuclei grow into crystal grains having the same crystal plane orientation, the crystal grains are combined in parallel to crystallize into single crystal silicon.
Single crystal silicon rods are the raw materials for the production of single crystal silicon wafers. With the rapid increase in the demand for monocrystalline silicon wafers in domestic and international markets, the market demand for monocrystalline silicon rods is also growing rapidly.
The single crystal silicon wafer is divided into 6 inches, 8 inches, 12 inches (300 mm), and 18 inches (450 mm) according to its diameter. The larger the diameter of the wafer, the more integrated circuits that can be engraved, and the lower the cost of the chip. But the requirements for materials and technology for larger wafers are higher. Single crystal silicon is divided into a Czochralski method (CZ), a zone melting method (FZ) and an epitaxial method according to different crystal growth methods. A single crystal silicon rod is grown by a straight pull method or a zone melting method, and a single crystal silicon film is grown by epitaxial method. The single crystal silicon grown by the Czochralski method is mainly used for a semiconductor integrated circuit, a diode, an epitaxial wafer substrate, and a solar cell. At present, the crystal diameter can be controlled at Φ3~8 inches. The zone melting single crystal is mainly used in the field of high voltage and high power controllable rectifier devices, and is widely used in series of products such as high power transmission and transformation, electric locomotive, rectification, frequency conversion, electromechanical integration, energy saving lamps and televisions. At present, the crystal diameter can be controlled at Φ3~6 inches. Epitaxial wafers are mainly used in the field of integrated circuits.
Czochralski (CZ) single crystal silicon materials are the most widely used due to cost and performance reasons. The materials used in the IC industry are mainly CZ polishing sheets and epitaxial wafers. Memory circuits typically use CZ pads because of the lower cost. Logic circuits generally use higher-priced epitaxial wafers, because they have the ability to be more squinting in the IC manufacturing industry.
Monocrystalline silicon, also known as silicon single crystal, is the most basic material in electronic information materials and belongs to the category of semiconductor materials. Monocrystalline silicon has penetrated into all areas of the national economy and national defense technology. Today, more than 95% of semiconductor devices and more than 99% of silicon for integrated circuits in the global $200 billion electronic communication semiconductor market.
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The larger the diameter of the silicon wafer, the higher the technical requirements, the more market prospects, the higher the value.
Japan, the United States and Germany are major producers of silicon materials. China's silicon materials industry started at the same time as Japan, but overall, the level of production technology is still relatively low, and most of them are 2.5, 3, 4, 5 inch silicon ingots and small diameter silicon wafers. Most of the integrated circuits and silicon wafers consumed by China still rely on imports. However, China's scientific and technological personnel are catching up and successfully produced 12-inch single crystal silicon in 1998, marking the beginning of a new development period of China's monocrystalline silicon production.
At present, the production capacity of monocrystalline silicon in the world is 10,000 tons/year, and the annual consumption is about 6,000 tons to 7,000 tons. In the next few years, the development of monocrystalline silicon materials in the world will show the following development trends.
The single crystal silicon product has a transition to 300mm, and the trend of large diameter is obvious:
With the development of semiconductor material technology, higher requirements are placed on the specifications and quality of silicon wafers, and the proportion of large-diameter silicon wafers suitable for microfabrication in the market will increase. At present, the mainstream product of silicon wafer is 200mm, and it gradually transitions to 300mm, and the development level reaches 400mm~450mm. According to statistics, the global use of 200mm silicon wafers accounts for about 60%, 150mm accounts for about 20%, and the rest accounts for about 20%. According to the latest International Semiconductor Technology Guide (ITRS), the next generation of 300mm silicon wafers has a diameter of 450mm; 450mm silicon wafers are the substrate material for the next 22nm linewidth 64G integrated circuits, which will directly affect the speed and cost of computers. And determine the integration of the central processing unit of the computer.
Gartner's five-year forecast for silicon demand shows that global 300mm wafers will increase from 1.3% in 2000 to 21.1% in 2006. Japan, the United States, South Korea and other countries have begun to gradually expand the production of 300mm wafers in 1999. According to incomplete statistics, there are about 40 300mm silicon device production lines currently under construction, under construction and planned to be built around the world, mainly in the United States and Taiwan, etc. There are more than 20 production lines in Taiwan alone, followed by Japan and Korea. , new and Europe.
According to a survey by the World Semiconductor Equipment and Materials Association (SEMI), in 2004 and 2005, the proportion of investment in 300mm production lines in all wafer production equipment will be 55% and 62%, respectively, and the investment amount will reach 130.3 respectively. Billions of dollars and 18.41 billion dollars have developed very rapidly. In 1996, this proportion was only zero.
2. The development of silicon material industry is becoming more and more international, group, and production is highly concentrated :
The increasing cost of R&D and construction, coupled with the advantages of existing marketing and branding, has led to the formation of “big and big†in the silicon material industry, and a small number of intensive large group companies monopolize the material market. In the late 1990s, the sales of the eight largest silicon companies controlled by capital in Japan, Germany and South Korea (mainly Japan and Germany) accounted for more than 90% of the world's wafer sales. According to the market share of the world's silicon material producers provided by SEMI in 2002, Shinetsu, SUMCO, Wacker, MEMC, Komatsu and other five companies accounted for 89% of the total market, and a monopoly position has been formed.
3. Silicon-based materials have become an important direction for the development of silicon materials industry:
With the development of optoelectronics and communication industry, silicon-based materials have become an important direction for the development of silicon materials industry. Silicon-based materials are fabricated on conventional silicon materials and are the development and continuation of conventional silicon materials. The device process is compatible with silicon processes. The main silicon-based materials include SOI (silicon on insulator), GeSi, and stress silicon. At present, SOI technology has begun to be widely used in the world. SOI materials account for about 30% of the entire semiconductor material market, and it is expected to account for about 50% of the market by 2010. Soitec's (the world's largest SOI producer)'s SOSI market forecast for 2000-2010 and the proportion of SOI wafers of various sizes in 2005 predicted the industry's development prospects.
4. Further upgrade of silicon wafer manufacturing technology:
At present, advanced cutting, grinding, polishing and clean packaging processes are widely used in the world, which has made significant progress in the production technology. In Japan, 50% of Φ200mm silicon wafers have been sliced ​​with a wire cutter, which not only improves the quality of the wafer, but also reduces the cutting loss by 10%. Large semiconductor manufacturers in Japan have already transitioned to 300mm silicon wafers and are developing to a micronization of 0.13μm or less. In addition, the introduction of the latest cutting-edge technology, trial production development of high-performance wafers such as SOI has also entered the mass production stage. In this regard, silicon wafer manufacturers have also increased their investment in equipment for 300mm silicon wafers. In order to further miniaturize the design rules, high-flatness silicon wafers and defect-free silicon wafers have also been developed, and the equipment has been improved.
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Silicon is the highest solid element in the earth's crust, and its content is one quarter of the earth's crust, but there is no single silicon in nature, mostly in oxide or silicate state. The atomic valence of silicon is mainly tetravalent, followed by divalent; its chemical properties are stable at room temperature, insoluble in a single strong acid, and easily soluble in alkali; it is chemically active at high temperatures and can be combined with many elements.
Due to the moderate band gap and electron mobility of silicon, the maximum operating temperature of silicon devices can reach 250 ° C, and the operating frequency of microwave power devices can reach C band (5 GHz). A dense and dense SiO2 film can be formed on the surface of silicon. This film can act as a dielectric of a capacitor, a diffusion isolation layer, and a protective layer on the surface of the device. With the advent of planar process and lithography, the ultra-large scale integrated circuit of silicon is promoted. development of. The silicon material is rich in resources and is a non-toxic elemental semiconductor material, which is easy to produce large-diameter dislocation-free low-micro defect single crystal. The crystal mechanical properties are superior and easy to realize industrialization, which leads to the semiconductor silicon material becoming the first major functional material in electronic materials, and will become the main material of semiconductor in the future.
Polysilicon material is an electronic material that has been purified by a series of physical and chemical reactions to obtain a certain purity. It is an extremely important intermediate product in the industrial chain of silicon products. It is a silicon polishing sheet, solar cell and high-purity silicon. The main raw materials for products are the most basic raw materials for the information industry and the new energy industry.
Polysilicon product classification:
Polysilicon can be classified into metallurgical grade (industrial silicon), solar grade, and electronic grade according to purity classification.
1. Metallurgical grade silicon (MG): It is a silicon oxide that is reduced by carbon in an electric arc furnace. Generally, Si is contained in an amount of 90 - 95% or more and 99.8% or more.
2. Solar grade silicon (SG): The purity is between metallurgical grade silicon and electronic grade silicon, which has not been clearly defined so far. It is generally considered that the content of Si is 99.99% - 99.9999% (4 to 6 9).
3, electronic grade silicon (EG): generally requires Si > 99.9999% or more, ultra high purity reached 99.9999999% ~ 99.999999999% (9 ~ 11 9). Its conductivity is between 10-4 – 1010 ohm cm.
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