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60-613: When it opened, Cestas was Europe's largest solar park. The power station comprises a million polycristalline silicon modules. The 300 MWp power station has an annual production of 350 GWh, equivalent to the household consumption (excluding heating) of the 240,000 inhabitants of Bordeaux yet represents less than 0.1% of annual electricity production in France. Alone, the power station has increased net solar power production in metropolitan France by 6% compared to 2014 (5,500 GWh). Twenty-five 12 MWp power stations are linked together and hooked up to

120-859: A bar or block using a mold chill method. A special case are polycrystalline or single crystal ingots made by pulling from a molten melt. Single crystal ingots (called boules ) of materials are grown (crystal growth) using methods such as the Czochralski process or Bridgeman technique . The boules may be either semiconductor (e.g. electronic chip wafers , photovoltaic cells ) or non-conducting inorganic compounds for industrial and jewelry use (e.g., synthetic ruby, sapphire). Single crystal ingots of metal are produced in similar fashion to that used to produce high purity semiconductor ingots, i.e. by vacuum induction refining. Single crystal ingots of engineering metals are of interest due to their very high strength due to lack of grain boundaries . The method of production

180-462: A consequence, in 2013 it imposed import tariffs of as much as 57 percent on polysilicon shipped from these two countries in order to stop the product from being sold below cost. Due to the rapid growth in manufacturing in China and the lack of regulatory controls, there have been reports of the dumping of waste silicon tetrachloride . Normally the waste silicon tetrachloride is recycled but this adds to

240-525: A cost-effective and faster alternative for producing solar-grade poly-Si thin films. Modules produced by such method are shown to have a photovoltaic efficiency of ~6%. Polysilicon doping, if needed, is also done during the deposition process, usually by adding phosphine, arsine, or diborane. Adding phosphine or arsine results in slower deposition, while adding diborane increases the deposition rate. The deposition thickness uniformity usually degrades when dopants are added during deposition. The Siemens process

300-502: A crystal grain size smaller than the device feature size is needed for homogeneity of the devices. Another method to produce poly-Si at low temperatures is metal-induced crystallization where an amorphous-Si thin film can be crystallized at temperatures as low as 150 °C if annealed while in contact of another metal film such as aluminium , gold , or silver . Polysilicon has many applications in VLSI manufacturing. One of its primary uses

360-426: A larger contact area. Molds may be either solid "massive" design, sand cast (e.g. for pig iron), or water-cooled shells, depending upon heat transfer requirements. Ingot molds are tapered to prevent the formation of cracks due to uneven cooling. A crack or void formation occurs as the liquid to solid transition has an associated volume change for a constant mass of material. The formation of these ingot defects may render

420-500: A low-pressure reactor either by changing the pumping speed or changing the inlet gas flow into the reactor. If the inlet gas is composed of both silane and nitrogen, the inlet gas flow, and hence the reactor pressure, may be varied either by changing the nitrogen flow at constant silane flow, or changing both the nitrogen and silane flow to change the total gas flow while keeping the gas ratio constant. Recent investigations have shown that e-beam evaporation, followed by SPC (if needed) can be

480-453: A minimum temperature, however, wherein the rate of deposition becomes faster than the rate at which unreacted silane arrives at the surface. Beyond this temperature, the deposition rate can no longer increase with temperature, since it is now being hampered by lack of silane from which the polysilicon will be generated. Such a reaction is then said to be "mass-transport-limited". When a polysilicon deposition process becomes mass-transport-limited,

540-512: A more efficient semiconductor than polycrystalline as it has undergone additional recrystallization via the Czochralski method. Polysilicon deposition, or the process of depositing a layer of polycrystalline silicon on a semiconductor wafer, is achieved by the chemical decomposition of silane (SiH 4 ) at high temperatures of 580 to 650 °C. This pyrolysis process releases hydrogen. Polysilicon layers can be deposited using 100% silane at

600-629: A power station. The issue of efficiency versus cost is a value decision of whether one requires an "energy dense" solar cell or sufficient area is available for the installation of less expensive alternatives. For instance, a solar cell used for power generation in a remote location might require a more highly efficient solar cell than one used for low-power applications, such as solar accent lighting or pocket calculators, or near established power grids. Polysilicon production by country in 2013 (company head-quarter, not location of facility). World total of 227,000 tonnes. The polysilicon manufacturing market

660-474: A pressure of 25–130 Pa (0.19–0.98 Torr) or with 20–30% silane (diluted in nitrogen) at the same total pressure. Both of these processes can deposit polysilicon on 10–200 wafers per run, at a rate of 10–20 nm/min and with thickness uniformities of ±5%. Critical process variables for polysilicon deposition include temperature, pressure, silane concentration, and dopant concentration. Wafer spacing and load size have been shown to have only minor effects on

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720-422: A useful final product. Non-metallic and semiconductor materials prepared in bulk form may also be referred to as ingots, particularly when cast by mold based methods. Precious metal ingots can be used as currency (with or without being processed into other shapes), or as a currency reserve, as with gold bars . Ingots are generally made of metal, either pure or alloy, heated past its melting point and cast into

780-434: A visible grain, a "metal flake effect". Semiconductor grade (also solar grade) polycrystalline silicon is converted to single-crystal silicon – meaning that the randomly associated crystallites of silicon in polycrystalline silicon are converted to a large single crystal. Single-crystal silicon is used to manufacture most Si-based microelectronic devices. Polycrystalline silicon can be as much as 99.9999% pure. Ultra-pure poly

840-671: Is a type of chemical vapor deposition process. Upgraded metallurgical-grade (UMG) silicon (also known as UMG-Si) for solar cells is being produced as a low cost alternative to polysilicon created by the Siemens process . UMG-Si greatly reduces impurities in a variety of ways that require less equipment and energy than the Siemens process. It is about 99% pure which is three or more orders of magnitude less pure and about 10 times less expensive than polysilicon ($ 1.70 to $ 3.20 per kg from 2005 to 2008 compared to $ 40 to $ 400 per kg for polysilicon). It has

900-457: Is as gate electrode material for MOS devices. A polysilicon gate's electrical conductivity may be increased by depositing a metal (such as tungsten) or a metal silicide (such as tungsten silicide) over the gate. Polysilicon may also be employed as a resistor, a conductor, or as an ohmic contact for shallow junctions, with the desired electrical conductivity attained by doping the polysilicon material. One major difference between polysilicon and a-Si

960-404: Is commonly used for the conducting gate materials in semiconductor devices such as MOSFETs ; however, it has potential for large-scale photovoltaic devices. The abundance, stability, and low toxicity of silicon, combined with the low cost of polysilicon relative to single crystals makes this variety of material attractive for photovoltaic production. Grain size has been shown to have an effect on

1020-742: Is deposited using low-pressure chemical-vapour deposition ( LPCVD ) reactors at high temperatures and is usually heavily doped n-type or p-type . More recently, intrinsic and doped polysilicon is being used in large-area electronics as the active and/or doped layers in thin-film transistors . Although it can be deposited by LPCVD , plasma-enhanced chemical vapour deposition (PECVD), or solid-phase crystallization of amorphous silicon in certain processing regimes, these processes still require relatively high temperatures of at least 300 °C. These temperatures make deposition of polysilicon possible for glass substrates but not for plastic substrates. The deposition of polycrystalline silicon on plastic substrates

1080-434: Is distinct from monocrystalline silicon and amorphous silicon . In single-crystal silicon, also known as monocrystalline silicon , the crystalline framework is homogeneous, which can be recognized by an even external colouring. The entire sample is one single, continuous and unbroken crystal as its structure contains no grain boundaries . Large single crystals are rare in nature and can also be difficult to produce in

1140-534: Is growing rapidly. According to Digitimes , in July 2011, the total polysilicon production in 2010 was 209,000 tons. First-tier suppliers account for 64% of the market while China-based polysilicon firms have 30% of market share. The total production is likely to increase 37.4% to 281,000 tons by end of 2011. For 2012, EETimes Asia predicts 328,000 tons production with only 196,000 tons of demand, with spot prices expected to fall 56%. While good for renewable energy prospects,

1200-404: Is motivated by the desire to be able to manufacture digital displays on flexible screens. Therefore, a relatively new technique called laser crystallization has been devised to crystallize a precursor amorphous silicon (a-Si) material on a plastic substrate without melting or damaging the plastic. Short, high-intensity ultraviolet laser pulses are used to heat the deposited a-Si material to above

1260-491: Is produced from metallurgical grade silicon by a chemical purification process, called the Siemens process . This process involves distillation of volatile silicon compounds, and their decomposition into silicon at high temperatures. An emerging, alternative process of refinement uses a fluidized bed reactor . The photovoltaic industry also produces upgraded metallurgical-grade silicon (UMG-Si), using metallurgical instead of chemical purification processes. When produced for

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1320-416: Is that the mobility of the charge carriers of the polysilicon can be orders of magnitude larger and the material also shows greater stability under electric field and light-induced stress. This allows more complex, high-speed circuitry to be created on the glass substrate along with the a-Si devices, which are still needed for their low- leakage characteristics. When polysilicon and a-Si devices are used in

1380-401: Is the most commonly used method of polysilicon production, especially for electronics, with close to 75% of the world's production using this process as of 2005. The process converts metallurgical-grade Si , of approximately 98% purity, to SiHCl 3 and then to silicon in a reactor, thus removing transition metal and dopant impurities. The process is relatively expensive and slow. It

1440-525: Is used in the semiconductor industry, starting from poly rods that are two to three meters in length. In the microelectronics industry (semiconductor industry), poly is used at both the macro and micro scales. Single crystals are grown using the Czochralski , zone melting and Bridgman–Stockbarger methods. At the component level, polysilicon has long been used as the conducting gate material in MOSFET and CMOS processing technologies. For these technologies it

1500-644: Is via single crystal dendrite and not via simple casting. Possible uses include turbine blades . In the United States, the brass and bronze ingot making industry started in the early 19th century. The US brass industry grew to be the number one producer by the 1850s. During colonial times the brass and bronze industries were almost non-existent because the British demanded all copper ore be sent to Britain for processing. Copper based alloy ingots weighed approximately 20 pounds (9.1 kg). Ingots are manufactured by

1560-693: Is yet unclear which companies will be able to produce at costs low enough to be profitable after the steep drop in spot-prices of the last months. Wacker's projected its total hyperpure-polysilicon production capacity to increase to 67,000 metric tons by 2014, due to its new polysilicon-production facility in Cleveland, Tennessee (US) with an annual capacity of 15,000 metric tons. Prices of polysilicon are often divided into two categories, contract and spot prices, and higher purity commands higher prices. While in booming installation times, price rally occurs in polysilicon. Not only spot prices surpass contract prices in

1620-494: The FIT policies of Italy. The solar PV price survey and market research firm, PVinsights, reported that the prices of polysilicon might be dragged down by lack of installation in the second half of 2011. As recently as 2008 prices were over $ 400/kg spiking from levels around $ 200/kg, while seen falling to $ 15/kg in 2013. The Chinese government accused United States and South Korean manufacturers of predatory pricing or "dumping" . As

1680-535: The RTE high voltage electricity transmission network. Thanks to the east–west panel orientation, production per hectare (of land, not modules) is two to three times greater than a comparable power station with south-facing modules, due to less space required between rows . The park's average surface power density is approximately 15 W per square metre, compared to 3–8 W recorded elsewhere in metropolitan France ( Losse , la Colle des Mées, Toul-Rosières , etc.). Neoen owns

1740-473: The Siemens process. GT Solar claims a new Siemens process can produce at $ 27/kg and may reach $ 20/kg in 5 years. GCL-Poly expects production costs to be $ 20/kg by end of 2011. Elkem Solar estimates their UMG costs to be $ 25/kg, with a capacity of 6,000 tonnes by the end of 2010. Calisolar expects UMG technology to produce at $ 12/kg in 5 years with boron at 0.3 ppm and phosphorus at 0.6 ppm. At $ 50/kg and 7.5 g/W, module manufacturers spend $ 0.37/W for

1800-426: The cast ingot useless and may need to be re-melted, recycled, or discarded. The physical structure of a crystalline material is largely determined by the method of cooling and precipitation of the molten metal. During the pouring process, metal in contact with the ingot walls rapidly cools and forms either a columnar structure or possibly a "chill zone" of equiaxed dendrites , depending upon the liquid being cooled and

1860-461: The cooling of a molten liquid (known as the melt) in a mold. The manufacture of ingots has several aims. Firstly, the mold is designed to completely solidify and form an appropriate grain structure required for later processing, as the structure formed by the cooling of the melt controls the physical properties of the material. Secondly, the shape and size of the mold is designed to allow for ease of ingot handling and downstream processing. Finally,

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1920-429: The cooling rate of the mold. For a top-poured ingot, as the liquid cools within the mold, differential volume effects cause the top of the liquid to recede leaving a curved surface at the mold top which may eventually be required to be machined from the ingot. The mold cooling effect creates an advancing solidification front, which has several associated zones, closer to the wall there is a solid zone that draws heat from

1980-418: The cost of manufacture as it needs to be heated to 1,800 °F (980 °C). Ingots An ingot is a piece of relatively pure material, usually metal , that is cast into a shape suitable for further processing. In steelmaking , it is the first step among semi-finished casting products . Ingots usually require a second procedure of shaping, such as cold/hot working, cutting, or milling to produce

2040-410: The cost. Not requiring a silicon wafer alleviates the silicon shortages occasionally faced by the microelectronics industry. An example of not using a silicon wafer is crystalline silicon on glass (CSG) materials A primary concern in the photovoltaics industry is cell efficiency. However, sufficient cost savings from cell manufacturing can be suitable to offset reduced efficiency in the field, such as

2100-495: The deposition process. The rate of polysilicon deposition increases rapidly with temperature, since it follows Arrhenius behavior, that is deposition rate = A·exp(–qE a /kT) where q is electron charge and k is the Boltzmann constant . The activation energy (E a ) for polysilicon deposition is about 1.7 eV. Based on this equation, the rate of polysilicon deposition increases as the deposition temperature increases. There will be

2160-410: The efficiency of polycrystalline solar cells. Solar cell efficiency increases with grain size. This effect is due to reduced recombination in the solar cell. Recombination, which is a limiting factor for current in a solar cell, occurs more prevalently at grain boundaries, see figure 1. The resistivity, mobility, and free-carrier concentration in monocrystalline silicon vary with doping concentration of

2220-436: The electronics industry, polysilicon contains impurity levels of less than one part per billion (ppb), while polycrystalline solar grade silicon (SoG-Si) is generally less pure. In the 2010's, production shifted toward China, with China-based companies accounting for seven of the top ten producers and around 90% of total worldwide production capacity of approximately 1,400,000 MT. German, US and South Korea companies account for

2280-402: The high voltage unit, the transformers and inverters. A just-in-time method was devised for construction, with tractor-towed platforms to transport panels. The project delivered significant numbers of construction jobs -up to 250 workers at peak activity. A total of 360 million euros was invested in the project. The variable supply of electricity is sold to EDF at €104.5 per MWh. In comparison,

2340-453: The laboratory (see also recrystallisation ). In contrast, in an amorphous structure the order in atomic positions is limited to short range. Polycrystalline and paracrystalline phases are composed of a number of smaller crystals or crystallites . Polycrystalline silicon (or semi-crystalline silicon, polysilicon, poly-Si, or simply "poly") is a material consisting of multiple small silicon crystals. Polycrystalline cells can be recognized by

2400-480: The land and is the project manager. The company has a 40% share in the power station, with the remaining 60% owned by other shareholders. Neoen entrusted a consortium led by Clemessy (branch of French group Eiffage ) with the design, construction and maintenance of the power station in partnership with Schneider Electric and the French branch of Krinner. Neoen has entrusted Clemessy with the operation and maintenance of

2460-621: The liquid melt alloy compositions. Continuous casting methods for ingot processing also exist, whereby a stationary front of solidification is formed by the continual take-off of cooled solid material, and the addition of a molten liquid to the casting process. Approximately 70 percent of aluminium ingots in the U.S. are cast using the direct chill casting process, which reduces cracking. A total of 5 percent of ingots must be scrapped because of stress induced cracks and butt deformation. Plano-convex ingots are widely distributed archaeological artifacts which are studied to provide information on

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2520-495: The logarithm of the deposition rate against the reciprocal of the absolute temperature in the surface-reaction-limited region results in a straight line whose slope is equal to –qE a /k. At reduced pressure levels for VLSI manufacturing, polysilicon deposition rate below 575 °C is too slow to be practical. Above 650 °C, poor deposition uniformity and excessive roughness will be encountered due to unwanted gas-phase reactions and silane depletion. Pressure can be varied inside

2580-426: The market; but it is also hard to acquire enough polysilicon. Buyers will accept down payment and long-term agreements to acquire a large enough volume of polysilicon. On the contrary, spot prices will be below contract prices once the solar PV installation is in a down trend. In late 2010, booming installation brought up the spot prices of polysilicon. In the first half of 2011, prices of polysilicon kept strong owing to

2640-460: The material its typical metal flake effect . While polysilicon and multisilicon are often used as synonyms, multicrystalline usually refers to crystals larger than one millimetre. Multicrystalline solar cells are the most common type of solar cells in the fast-growing PV market and consume most of the worldwide produced polysilicon. About 5 tons of polysilicon is required to manufacture one 1 megawatt (MW) of conventional solar modules. Polysilicon

2700-435: The melting point of silicon, without melting the entire substrate. The molten silicon will then crystallize as it cools. By precisely controlling the temperature gradients, researchers have been able to grow very large grains, of up to hundreds of micrometers in size in the extreme case, although grain sizes of 10 nanometers to 1 micrometer are also common. In order to create devices on polysilicon over large-areas, however,

2760-452: The mold is designed to minimize melt wastage and aid ejection of the ingot, as losing either melt or ingot increases manufacturing costs of finished products. A variety of designs exist for the mold, which may be selected to suit the physical properties of the liquid melt and the solidification process. Molds may exist in the top, horizontal or bottom-up pouring and may be fluted or flat walled. The fluted design increases heat transfer owing to

2820-402: The overall cost of the project, were supplied by the world's top three manufacturers ( Yingli Solar , Trina Solar and Canadian Solar ), at the time the only companies able to supply the required volume and homogeneity. Neoen turned to French companies for the electrical installation: Clemessy, a branch of Eiffage, oversaw the project, Nexans supplied the 4000 km of cable and Schneider Electric

2880-418: The polycrystalline grains which will vary the physical properties of the material. The use of polycrystalline silicon in the production of solar cells requires less material and therefore provides higher profits and increased manufacturing throughput. Polycrystalline silicon does not need to be deposited on a silicon wafer to form a solar cell, rather it can be deposited on other-cheaper materials, thus reducing

2940-626: The polysilicon. For comparison, if a CdTe manufacturer pays spot price for tellurium ($ 420/kg in April 2010) and has a 3  μm thickness, their cost would be 10 times less, $ 0.037/Watt. At 0.1 g/W and $ 31/ozt for silver, polysilicon solar producers spend $ 0.10/W on silver. Q-Cells, Canadian Solar, and Calisolar have used Timminco UMG. Timminco is able to produce UMG-Si with 0.5 ppm boron for $ 21/kg but were sued by shareholders because they had expected $ 10/kg. RSI and Dow Corning have also been in litigation over UMG-Si technology. Currently, polysilicon

3000-451: The potential to provide nearly-as-good solar cell efficiency at 1/5 the capital expenditure, half the energy requirements, and less than $ 15/kg. In 2008 several companies were touting the potential of UMG-Si, but in 2010 the credit crisis greatly lowered the cost of polysilicon and several UMG-Si producers put plans on hold. The Siemens process will remain the dominant form of production for years to come due to more efficiently implementing

3060-437: The price announced for the non-variable supply from the planned Hinkley Point C nuclear power station is €109 (£92.50) per MWh at 2012 prices. Polycrystalline silicon Polycrystalline silicon , or multicrystalline silicon , also called polysilicon , poly-Si , or mc-Si , is a high purity, polycrystalline form of silicon , used as a raw material by the solar photovoltaic and electronics industry . Polysilicon

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3120-532: The reaction rate becomes dependent primarily on reactant concentration, reactor geometry, and gas flow. When the rate at which polysilicon deposition occurs is slower than the rate at which unreacted silane arrives, then it is said to be surface-reaction-limited. A deposition process that is surface-reaction-limited is primarily dependent on reactant concentration and reaction temperature. Deposition processes must be surface-reaction-limited because they result in excellent thickness uniformity and step coverage. A plot of

3180-512: The remainder. The polysilicon feedstock – large rods, usually broken into chunks of specific sizes and packaged in clean rooms before shipment – is directly cast into multicrystalline ingots or submitted to a recrystallization process to grow single crystal boules . The boules are then sliced into thin silicon wafers and used for the production of solar cells , integrated circuits and other semiconductor devices . Polysilicon consists of small crystals , also known as crystallites , giving

3240-431: The same process, this is called hybrid processing. A complete polysilicon active layer process is also used in some cases where a small pixel size is required, such as in projection displays . Polycrystalline silicon is the key feedstock in the crystalline silicon based photovoltaic industry and used for the production of conventional solar cells . For the first time, in 2006, over half of the world's supply of polysilicon

3300-406: The single crystal silicon. Whereas the doping of polycrystalline silicon does have an effect on the resistivity, mobility, and free-carrier concentration, these properties strongly depend on the polycrystalline grain size, which is a physical parameter that the material scientist can manipulate. Through the methods of crystallization to form polycrystalline silicon, an engineer can control the size of

3360-580: The solar plant. Construction began in November 2014 and the power station was commissioned in October 2015. The park was officially opened on 1 December 2015 . The power station is directly linked to the electricity transmission network. Supply to French electricity provider EDF was set at €105 per MWh for a period of 20 years – cheaper than the production of the planned European Pressurized nuclear Reactors (EPR) . The solar panels at Cestas, which represent 45% of

3420-411: The solidifying melt, for alloys there may exist a "mushy" zone, which is the result of solid-liquid equilibrium regions in the alloy's phase diagram , and a liquid region. The rate of front advancement controls the time that dendrites or nuclei have to form in the solidification region. The width of the mushy zone in an alloy may be controlled by tuning the heat transfer properties of the mold or adjusting

3480-407: The subsequent drop in price could be brutal for manufacturers. As of late 2012, SolarIndustryMag reports a capacity of 385,000 tons will be reached by yearend 2012. But as established producers (mentioned below) expand their capacities, additional newcomers – many from Asia – are moving into the market. Even long-time players in the field have recently had difficulties expanding plant production. It

3540-417: The use of larger solar cell arrays compared with more compact/higher efficiency designs. Designs such as CSG are attractive because of a low cost of production even with reduced efficiency. Higher efficiency devices yield modules that occupy less space and are more compact; however, the 5–10% efficiency of typical CSG devices still makes them attractive for installation in large central-service stations, such as

3600-411: Was being used by PV manufacturers. The solar industry was severely hindered by a shortage in supply of polysilicon feedstock and was forced to idle about a quarter of its cell and module manufacturing capacity in 2007. Only twelve factories were known to produce solar-grade polysilicon in 2008; however, by 2013 the number increased to over 100 manufacturers. Monocrystalline silicon is higher priced and

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