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| [[Image:Czochralski Process.svg|thumb|right|350px|The Czochralski process]]
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| {{Crystallization}}
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| The '''Czochralski process''' is a method of [[crystal growth]] used to obtain [[single crystal]]s of [[semiconductors]] (e.g. [[silicon]], [[germanium]] and [[gallium arsenide]]), metals (e.g. [[palladium]], [[platinum]], [[silver]], [[gold]]), salts and synthetic [[gemstone]]s. The process is named after Polish scientist [[Jan Czochralski]],<ref>(Polish), (English), Paweł Tomaszewski, ""Jan Czochralski i jego metoda" (ang.Jan Czochralski and his method), Oficyna Wydawnicza ATUT, Wrocław–Kcynia 2003, ISBN 83-89247-27-5</ref> who invented the method in 1916 while investigating the crystallization rates of metals.<ref>J. Czochralski (1918) "Ein neues Verfahren zur Messung der Kristallisationsgeschwindigkeit der Metalle" [A new method for the measurement of the crystallization rate of metals], ''Zeitschrift für Physikalische Chemie'', '''92''' : 219–221.</ref>
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| The most important application may be the growth of large cylindrical [[ingot]]s, or [[boule (crystal)|boules]], of [[Monocrystalline silicon|single crystal silicon]]. Other semiconductors, such as [[gallium arsenide]], can also be grown by this method, although lower defect densities in this case can be obtained using variants of the [[Bridgman-Stockbarger technique]].
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| ==Production of Czochralski silicon==
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| [[Image:Silicon seed crystal puller rod.jpg|thumb|left|A puller rod with [[seed crystal]] for growing [[Single crystal|single-crystal]] [[silicon]] by the Czochralski process]]
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| High-purity, [[semiconductor]]-grade silicon (only a few parts per million of impurities) is melted in a [[crucible]], usually made of [[quartz]]. Dopant impurity atoms such as [[boron]] or [[phosphorus]] can be added to the molten silicon in precise amounts to [[Doping (semiconductor)|dope]] the silicon, thus changing it into [[P-type semiconductor|p-type]] or [[N-type semiconductor|n-type]] silicon, with different electronic properties. A precisely oriented rod-mounted [[seed crystal]] is dipped into the molten silicon. The seed crystal's rod is slowly pulled upwards and rotated simultaneously. By precisely controlling the temperature gradients, rate of pulling and speed of rotation, it is possible to extract a large, single-crystal, cylindrical ingot from the melt. Occurrence of unwanted instabilities in the melt can be avoided by investigating and visualizing the temperature and velocity fields during the crystal growth process.<ref>{{cite journal |first=J. |last=Aleksic |last2=et al. |title=Temperature and Flow Visualization in a Simulation of the Czochralski Process Using Temperature-Sensitive Liquid Crystals |journal=[[Annals of the New York Academy of Sciences|Ann. of NY Academy of Sci.]] |volume=972 |issue= |year=2002 |pages=158 |doi=10.1111/j.1749-6632.2002.tb04567.x |bibcode = 2002NYASA.972..158A |first2=Paul |last3=Szymczyk |first3=Janusz A. }}</ref> This process is normally performed in an [[inert]] atmosphere, such as [[argon]], in an inert chamber, such as [[quartz]].
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| ==Size of crystals==
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| Due to the efficiencies of common [[wafer (electronics)|wafer]] specifications, the semiconductor industry has used wafers with standardized dimensions. In the early days, the boules were smaller, only a few inches wide. With advanced technology, high-end device manufacturers use 200 mm and 300 mm diameter wafers. The width is controlled by precise control of the temperature, the speeds of rotation and the speed the seed holder is withdrawn. The crystal ingots from which these wafers are sliced can be up to 2 metres in length, weighing several hundred kilogrammes. Larger wafers allow improvements in manufacturing efficiency, as more chips can be fabricated on each wafer, so there has been a steady drive to increase silicon wafer sizes. The next step up, 450 mm, is currently scheduled for introduction in 2018.<ref>[http://www.electronicsweekly.com/news/business/doubts-over-450mm-and-euv-2013-12/ Doubts over 450mm and EUV]. Electronicsweekly.com. December 30, 2013. Retrieved on 2014-01-09.</ref> Silicon wafers are typically about 0.2–0.75 mm thick, and can be polished to great flatness for making [[integrated circuit]]s or textured for making [[solar cell]]s.
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| The process begins when the chamber is heated to approximately 1500 degrees Celsius, melting the silicon. When the silicon is fully melted, a small seed crystal mounted on the end of a rotating shaft is slowly lowered until it just dips below the surface of the molten silicon. The shaft rotates counterclockwise and the crucible rotates clockwise. The rotating rod is then drawn upwards very slowly, allowing a roughly cylindrical boule to be formed. The boule can be from one to two metres, depending on the amount of silicon in the crucible.
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| The electrical characteristics of the silicon are controlled by adding material like phosphorus or boron to the silicon before it is melted. The added material is called dopant and the process is called doping. This method is also used with semiconductor materials other than silicon, such as gallium arsenide.
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| Monocrystalline silicon grown by the Czochralski process is the basic material in the production of the large-scale integrated circuit chips used in computers, TVs, mobile phones and all types of electronic equipment.<ref>[http://www.bbc.co.uk/dna/h2g2/A912151 Czochralski Crystal Growth Method]. Bbc.co.uk. 30 January 2003. Retrieved on 2011-12-06.</ref> Monocrystalline silicon is also used in large quantity for producing photovoltaic solar cells. The almost perfect crystal structure yields the highest light-to-electricity conversion efficiency for silicon.
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| ==Impurity incorporation==
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| When silicon is grown by the Czochralski method, the melt is contained in a [[silica]] ([[quartz]]) crucible. During growth, the walls of the crucible dissolve into the melt and Czochralski silicon therefore contains [[oxygen]] at a typical concentration of 10{{su|p=18}} cm{{su|p=−3}}. Oxygen impurities can have beneficial effects. Carefully chosen annealing conditions can allow the formation of oxygen [[precipitates]]. These have the effect of trapping unwanted [[transition metal]] impurities in a process known as [[gettering]]. Additionally, oxygen impurities can improve the mechanical strength of silicon wafers by immobilising any [[dislocations]] which may be introduced during device processing. It was experimentally shown in the 1990s that the high oxygen concentration is also beneficial for [[radiation hardness]] of silicon [[particle detector]]s used in harsh radiation environment (such as [[CERN]]'s [[Large Hadron Collider|LHC]]/[[S-LHC]] projects).<ref>{{cite journal|doi=10.1109/23.211360 |title=Investigation of the oxygen-vacancy (A-center) defect complex profile in neutron irradiated high resistivity silicon junction particle detectors|year=1992|last1=Li|first1=Z.|last2=Kraner|first2=H.W.|last3=Verbitskaya|first3=E.|last4=Eremin|first4=V.|last5=Ivanov|first5=A.|last6=Rattaggi|first6=M.|last7=Rancoita|first7=P.G.|last8=Rubinelli|first8=F.A.|last9=Fonash|first9=S.J.|journal=IEEE Transactions on Nuclear Science|volume=39|issue=6|pages=1730|bibcode = 1992ITNS...39.1730L |display-authors=9 |last10=Dale |first10=C. |last11=Marshall |first11=P. }}</ref><ref>{{cite journal|doi=10.1016/S0168-9002(01)00560-5|title=Radiation hard silicon detectors—developments by the RD48 (ROSE) collaboration|year=2001|last1=Lindström|first1=G|journal=Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|volume=466|issue=2|pages=308|bibcode = 2001NIMPA.466..308L |last2=Ahmed|first2=M|last3=Albergo|first3=S|last4=Allport|first4=P|last5=Anderson|first5=D|last6=Andricek|first6=L|last7=Angarano|first7=M.M|last8=Augelli|first8=V|last9=Bacchetta|first9=N|last10=Bartalini|first10=P|last11=Bates|first11=R|last12=Biggeri|first12=U|last13=Bilei|first13=G.M|last14=Bisello|first14=D|last15=Boemi|first15=D|last16=Borchi|first16=E|last17=Botila|first17=T|last18=Brodbeck|first18=T.J|last19=Bruzzi|first19=M|last20=Budzynski|first20=T|last21=Burger|first21=P|last22=Campabadal|first22=F|last23=Casse|first23=G|last24=Catacchini|first24=E|last25=Chilingarov|first25=A|last26=Ciampolini|first26=P|last27=Cindro|first27=V|last28=Costa|first28=M.J|last29=Creanza|first29=D|last30=Clauws|first30=P}}</ref> Therefore, radiation detectors made of Czochralski- and Magnetic Czochralski-silicon are considered to be promising candidates for many future [[high-energy physics]] experiments.<ref>CERN RD50 Status Report 2004, CERN-LHCC-2004-031 and LHCC-RD-005 and cited literature therein</ref><ref>{{cite journal|doi=10.1016/j.nima.2005.01.057|title=Particle detectors made of high-resistivity Czochralski silicon|year=2005|last1=Harkonen|first1=J|last2=Tuovinen|first2=E|last3=Luukka|first3=P|last4=Tuominen|first4=E|last5=Li|first5=Z|last6=Ivanov|first6=A|last7=Verbitskaya|first7=E|last8=Eremin|first8=V|last9=Pirojenko|first9=A|journal=Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|volume=541|pages=202|bibcode = 2005NIMPA.541..202H |last10=Riihimaki|first10=I.|last11=Virtanen|first11=A.}}</ref> It has also been shown that presence of oxygen in silicon increases impurity trapping during post-implantation annealing processes.<ref>{{cite journal|doi=10.1063/1.356173|title=Erbium in crystal silicon: Segregation and trapping during solid phase epitaxy of amorphous silicon|year=1994|last1=Custer|first1=J. S.|last2=Polman|first2=A.|last3=Van Pinxteren|first3=H. M.|journal=Journal of Applied Physics|volume=75|issue=6|pages=2809|bibcode = 1994JAP....75.2809C }}</ref>
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| However, oxygen impurities can react with boron in an illuminated environment, such as experienced by solar cells. This results in the formation of an electrically active boron–oxygen complex that detracts from cell performance. Module output drops by approximately 3% during the first few hours of light exposure.<ref>Eikelboom, J.A., Jansen, M.J., 2000. [http://www.ecn.nl/docs/library/report/2000/c00067.pdf Characteristion of PV modules of new generations; results of tests and simulations]. Report ECN-C-00-067, 18.</ref>
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| ===Mathematical expression of impurity incorporation from melt===
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| The impurity concentration in the solid crystal that results from freezing an incremental amount of volume can be obtained from consideration of the segregation coefficient.<ref>James D. Plummer, Michael D. Deal, and Peter B. Griffin, ''Silicon VLSI Technology,'' Prentice Hall, 2000, ISBN 0-13-085037-3 pp. 126–27</ref>
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| :<math>k_O</math>: Segregation coefficient
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| :<math>V_0</math>: Initial volume
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| :<math>I_0</math>: Number of impurities
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| :<math>C_0</math>: Impurity concentration in the melt
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| :<math>V_L</math>: Volume of the melt
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| :<math>I_L</math>: Number of impurities in the melt
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| :<math>C_L</math>: Concentration of impurities in the melt
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| :<math>V_S</math>: Volume of solid
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| :<math>C_S</math>: Concentration of impurities in the solid
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| During the growth process, volume of melt <math>dV</math> freezes, and there are impurities from the melt that are removed.
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| :<math>dI = -k_O C_L dV\;</math>
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| :<math>dI = - k_O \frac{I_L}{V_O - V_S} dV</math>
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| :<math>\int_{I_O}^{I_L} \frac{dI}{I_L} = -k_O \int_{0}^{V_S} \frac{dV}{V_O - V_S}</math>
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| :<math>\ln \left ( \frac{I_L}{I_O} \right ) = \ln \left ( 1 - \frac{V_S}{V_O} \right )^{k_O}</math>
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| :<math>I_L = I_O \left ( 1 - \frac{V_S}{V_O} \right )^{k_O}</math>
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| :<math>C_S = - \frac{dI_L}{dV_S}</math>
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| :<math>C_S = C_O k_O (1-f)^{k_o - 1}</math>
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| :<math>f = V_S / V_O\;</math>
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| ==Gallery==
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| {{Commons category|Czochralski method}}
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| <gallery>
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| Image:Czochralski method crucibles.jpg|Crucibles used in Czochralski method
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| Image: Czochralski method used crucible 1.jpg|Crucible after being used
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| Image:Monokristalines Silizium für die Waferherstellung.jpg|Silicon ingot
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| </gallery>
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| ==See also==
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| * [[Monocrystalline silicon]]
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| * [[Bridgman–Stockbarger technique]]
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| * [[Float-zone silicon]]
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| * [[Laser-heated pedestal growth]]
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| * [[Micro-Pulling-Down]]
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| ==References==
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| <!-- this 'empty' section displays references defined elsewhere -->
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| {{reflist}}
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| ==External links==
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| * [http://www.articleworld.org/index.php/Czochralski_process Czochralski doping process]
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| * {{youtube|LWfCqpJzJYM|Silicon Wafer Processing Animation}}
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| {{DEFAULTSORT:Czochralski Process}}
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| [[Category:Industrial processes]]
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| [[Category:Semiconductor growth]]
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| [[Category:Crystals]]
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| [[Category:Science and technology in Poland]]
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| [[Category:Polish inventions]]
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I'm Lawerence and I live in a seaside city in northern Germany, Barnstorf. I'm 32 and I'm will soon finish my study at Educational Studies.
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