Abstract because of its ability to produce silicon crystals of exceptionally high purity and crystallographic perfection, the floatzone method lends itself to. In the vertical configuration molten silicon has sufficient surface tension to keep the charge from separating. Numerical model for calculation of thermal stress in the crystal during growth using the developed setup. Superheating is not possible very slight supercooling required for growth s h at equilibrium g. The importance of zone melting for bulk crystal growth is mainly limited to its use for purification of the feed material but not to the growth process itself. Crystal growth processes based on capillarity closely examines crystal growth technologies, like czochralski, floating zone, and bridgman. The floatzone process, as typically practiced, involves creating a melt zone through a limited cross section of a silicon rod and passing this melt zone along the length of the silicon rod. Casey national renewable energy laboratory, golden, co 80401 usa abstract czochralski cz and floatzone fz crystals were grown from experimental solargrade silicon sogsi. The table below compares the characteristics of the fz and cz methods. The singlecrystal growth methods, floatzoning fz and czochralski growth cz, are relatively wellknown, so only some aspects pertinent to pv applications will be addressed here. The float zone fz technique for crystal growth has been widely used since its first application to silicon in order to avoid container contamination. Float zone growth of silicon crystals is known as the method for providing excellent material properties.
Floatzone silicon is very pure silicon obtained by vertical zone melting. A necking process is carried out to establish a dislocation free crystal before the neck is allowed to increase in diameter to form a taper and reach the desired diameter for steadystate growth. Thermal stress in fzlike growth setup reduced down to levels that allowed partially monocrystalline. For fz growth, a molten zone is held in place between two vertical solid rods by its own surface tension, as shown schematically in fig. Avoidance of the necessity of a containment vessel prevents. The basic feature of this growth technique is that the molten part of. Single crystal growth of silicon by float zone fz and.
As float zone silicon typically is used for power electronic components and detectors, the advantage of using largediameter substrates has been limited, and even today the majority of all float zone crystals are only 100125 mm in diameter, which is advantageous for the pv industry needs. Including practical examples and software applications, this book provides both theoretical and experimental sections. Pdf by use of the floatzone crystal growth method, silicon crystal of higher purity and longer minority carrier lifetime can be manufactured. With a neat diagram explain float zone technique of. Brice, the growth of crystals from the melt, north holand. Impurities with a segregation coefficient k 0 national renewable energy laboratory golden, colorado 80401 u. Casey national renewable energy laboratory, golden, co 80401 usa abstract czochralski cz and float zone fz crystals were grown from experimental solargrade silicon sogsi. The vg s voronkov number, where g s is the axial temperature gradient at the monocrystalmelt interface, is thus.
Keep reading for an answer straight from a reputable float zone wafer supplier. Crystal growth with the float zone method principle of the float zone method a monocrystalline silicon seed crystal is brought into contact with one end of a polycrystalline silicon ingot in the. When the melt is initially contacted with a monocrystal silicon seed, the resulting ingot is composed of monocrystalline silicon. Optical floating zone growth of single crystal rfe 2o 3 from a cafe 4o 7based solvent ann n. Francesca ferrazza, in practical handbook of photovoltaics second edition, 2012. Fzt 7 crystalgrowth equilibrium in crystal growth the crystal grown must be thermodynamically stable at t and p of crystallization.
Starting from here, an rf coil melts a small region of the polysilicon which, after cooling down, forms monocrystalline silicon with the crystallographic orientation of the seed crystal e. The uptodate reference contains detailed technical and applied information, especially on the difficulty of crystal shape control. Typically, the growth rate for float zone growth is 23 times higher than czochralski growth rates. Float zone silicon is a highpurity alternative to crystals grown by the czochralski process. The float zone process is run at significantly higher growth rates v than is the czochralski process. The production takes place under vacuum or in an inert gaseous atmosphere. The float zone method is the goto technique whenever a wafer requires highpurity silicon with little impurities. This image is a derivative work of the following images.
The process was developed at bell labs by henry theuerer in 1955 as a modification of a method developed by william gardner pfann for germanium. Pdf by use of the float zone crystal growth method, silicon crystal of higher purity and longer minority carrier lifetime can be manufactured. Singlecrystal ingot growth the singlecrystal growth methods, floatzoning fz and czochralski growth cz, are relatively wellknown, so only some aspects pertinent to pv applications will be addressed here. The basic idea in float zone fz crystal growth is to move a liquid zone through the material. Floatzone and czochralski crystal growth and diagnostic. This file is licensed under the creative commons attributionshare alike 4. A monocrystalline silicon seed crystal is brought into contact with one end of a polycrystalline silicon ingot. Float zone wafer supplier what is the float zone method. Floatzone growth of silicon crystals using largearea. Marks institute for environmental catalysis, department of materials science and engineering. As the molten zone is moved along the polysilicon rod, the molten silicon solidifies into a single crystal and, simultaneously, the material is purified.
Crystal growth optical floating zone growth of single. Float zone processing of particulate silicon hemlock. Dopants with ks crystal growth by floating zone technique mylene sage m. Basic principle of this technique is the radiofrequency induction heating, main aspects of. Float zone growth of silicon crystals using largearea seeding.
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