Polycrystalline silicon or polysilicon or poly-Si or simply poly (in context) is a material consisting of multiple small silicon crystals, and has long been used as the conducting gate material in MOSFET and CMOS processing technologies. For these technologies it is deposited using LPCVD reactors at high temperatures and is usually heavily N or P-doped. General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance as coarse powder, dark gray with bluish tinge Atomic mass 28. ... Quartz crystal Copper(II) sulfate and iodine crystal Synthetic bismuth crystal Insulin crystals Gallium, a metal that easily forms large single crystals A huge monocrystal of potassium dihydrogen phosphate grown from solution by Saint-Gobain for the megajoule laser of CEA. In chemistry and mineralogy, a crystal is a solid... The metal-oxide-semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), is by far the most common field-effect transistor in both digital and analog circuits. ... Static CMOS Inverter Complementary-symmetry/metal-oxide semiconductor (CMOS) (see-moss, IPA:), is a major class of integrated circuits. ... DC plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus. ... An N-type semiconductor is obtained by carrying out a process of doping, that is adding a certain type of atoms to the semiconductor in order to increase the number of free (in this case negative) charge carriers. ... A P-type semiconductor is obtained by carrying out a process of doping, that is adding a certain type of atoms to the semiconductor in order to increase the number of free (in this case positive) charges. ...

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 low-pressure chemical-vapour deposition (LPCVD), plasma-enhanced chemical vapour deposition (PECVD), or solid-phase crystallization (SPC) 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 drive to deposit Polycrystalline silicon or poly-Si on plastic substrates is powered 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 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 nanometres to 1 micrometre are also common. In order to create devices on polysilicon over large-areas however, 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 150C if annlead while in contact of another metal film such as aluminum, gold, or silver Roll-to-roll processing, also known as web processing, is the process of creating electronic devices on a roll of flexible plastic or metal foil. ... A thin film transistor (TFT) is a special kind of field effect transistor made by depositing thin films for the metallic contacts, semiconductor active layer, and dielectric layer. ... DC plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus. ... DC plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus. ... Amorphous silicon (a-Si) is the non-crystalline allotropic form of silicon. ... Celsius relates to the Celsius or centrigrade temperature scale. ... Glass can be made transparent and flat, or into other shapes and colors as shown in this sphere from the Verrerie of Brehat in Brittany. ... Household items made out of plastic. ... Amorphous silicon (a-Si) is the non-crystalline allotropic form of silicon. ... The solar corona as seen in deep ultraviolet light at 17. ... A LASER (acronym for Light Amplification by Stimulated Emission of Radiation) is an optical source that emits photons in a coherent beam. ... A metre (American spelling: meter; symbol: m) is a unit of length and the current base unit of length in the International System of Units (SI). ... A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the size of a droplet of mist or fog. ... Metal-induced crystallization (MIC) is a method by which amorphous silicon, or a-Si, can be turned into polycrystalline silicon at relatively low temperatures. ... Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ... General Name, Symbol, Number gold, Au, 79 Chemical series transition metals Group, Period, Block 11, 6, d Appearance metallic yellow Atomic mass 196. ... General Name, Symbol, Number silver, Ag, 47 Chemical series transition metals Group, Period, Block 11, 5, d Appearance lustrous white metal Atomic mass 107. ...

The main advantage of polysilicon over a-Si is that the mobility of the charge carriers 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 circuity 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 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. Charge carrier denotes in physics a free (mobile, unbound) particle carrying an electric charge. ... It has been suggested that optical field be merged into this article or section. ... The term leakage has numerous definitions: In normal usage, leakage is the diffusion of energy or matter out of a container. ... Liquid crystal on silicon (LCOS or LCoS) is a micro-projection or micro-display technology typically applied in projection televisions. ...

Polysilicon is a key component for integrated circuit and central processing unit manufacturers such as AMD and Intel, however it is also a key component of solar panel construction. The photovoltaic solar industry is growing rapidly but is likely going to be very limited in 2006-2008 due to severe shortages and allocations of the polysilicon material. Currently in 2006, 30% of the world's supply of polysilicon is being used for production of renewable electricity solar power panels. Silicon, one of the most common elements on the planet, is the basic component of polysilicon. With investment in polysilicon production plants the future expansion of a cost effective solar electricity supply (the ultimate renewable resource) will be possible. Integrated circuit showing memory blocks, logic and input/output pads around the periphery Microchips with a transparent window showing the integrated circuit inside. ... CPU redirects here. ... Advanced Micro Devices, Inc. ... Intel Corporation (NASDAQ: INTC, SEHK: 4335), founded in 1968 as Integrated Electronics Corporation, is an American multinational corporation that is best known for designing and manufacturing microprocessors and specialized integrated circuits. ... A photovoltaic (PV) module that is composed of multiple PV cells. ... A solar cell, a form of photovoltaic cell, is a device that uses the photoelectric effect to generate electricity from light, thus generating solar power (energy). ... Solar power describes a number of methods of harnessing energy from the light of the sun. ... General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance as coarse powder, dark gray with bluish tinge Atomic mass 28. ...

Major polysilicon manufacturers include Hemlock Semiconductor, Wacker Chemie, REC, Tokuyama, MEMC, Mitsubishi (Japan and America) and Sumitomo-Titanium, as well as several small site in China and CIS. The first 7 companies cover over 75 % of the worldwide production capacity of polysilicon (2006).

See also

• nanocrystalline silicon
• amorphous silicon
• photovoltaic cells

Nanocrystalline silicon (nc-Si) is similar to amorphous silicon (a-Si), in that it has an amorphous phase. ... Amorphous silicon (a-Si) is the non-crystalline allotropic form of silicon. ... A photovoltaic cell is a device that turns light into electric energy. ...

External links

• The US Display Consortium, promoting the development of polycrystalline silicon flat-panel display technologies
• The Coming Boom in Photovoltaic Power
• Alan Joch. "Sand Trap: Will the silicon shortage stunt the solar industry’s growth?", Plenty Magazine, Nov 10, 2006.