Crystal growth optical floating zone growth of single. Fzt 7 crystalgrowth equilibrium in crystal growth the crystal grown must be thermodynamically stable at t and p of crystallization. Optical floating zone growth of single crystal rfe 2o 3 from a cafe 4o 7based solvent ann n. A monocrystalline silicon seed crystal is brought into contact with one end of a polycrystalline silicon ingot.
Float zone growth of silicon crystals is known as the method for providing excellent material properties. The basic feature of this growth technique is that the molten part of. Floatzone growth of silicon crystals using largearea. 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. The vg s voronkov number, where g s is the axial temperature gradient at the monocrystalmelt interface, is thus. 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. Numerical model for calculation of thermal stress in the crystal during growth using the developed setup. With a neat diagram explain float zone technique of. Basic principle of this technique is the radiofrequency induction heating, main aspects of. Casey national renewable energy laboratory, golden, co 80401 usa abstract czochralski cz and float zone fz crystals were grown from experimental solargrade silicon sogsi. Including practical examples and software applications, this book provides both theoretical and experimental sections. Float zone wafer supplier what is the float zone method. Float zone silicon is a highpurity alternative to crystals grown by the czochralski process.
Float zone processing of particulate silicon hemlock. Crystal growth processes based on capillarity closely examines crystal growth technologies, like czochralski, floating zone, and bridgman. Floatzone and czochralski crystal growth and diagnostic. Single crystal growth of silicon by float zone fz and. Casey national renewable energy laboratory, golden, co 80401 usa abstract czochralski cz and floatzone fz crystals were grown from experimental solargrade silicon sogsi.
Pdf by use of the float zone crystal growth method, silicon crystal of higher purity and longer minority carrier lifetime can be manufactured. As the molten zone is moved along the polysilicon rod, the molten silicon solidifies into a single crystal and, simultaneously, the material is purified. The table below compares the characteristics of the fz and cz methods. Thermal stress in fzlike growth setup reduced down to levels that allowed partially monocrystalline. This image is a derivative work of the following images. In the vertical configuration molten silicon has sufficient surface tension to keep the charge from separating. Pdf by use of the floatzone crystal growth method, silicon crystal of higher purity and longer minority carrier lifetime can be manufactured. Abstract because of its ability to produce silicon crystals of exceptionally high purity and crystallographic perfection, the floatzone method lends itself to. 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. Typically, the growth rate for float zone growth is 23 times higher than czochralski growth rates. 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.
The uptodate reference contains detailed technical and applied information, especially on the difficulty of crystal shape control. Marks institute for environmental catalysis, department of materials science and engineering. Brice, the growth of crystals from the melt, north holand. When the melt is initially contacted with a monocrystal silicon seed, the resulting ingot is composed of monocrystalline silicon. This file is licensed under the creative commons attributionshare alike 4. 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. The production takes place under vacuum or in an inert gaseous atmosphere. Superheating is not possible very slight supercooling required for growth s h at equilibrium g. The basic idea in float zone fz crystal growth is to move a liquid zone through the material. 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. Floatzone silicon is very pure silicon obtained by vertical zone melting. Impurities with a segregation coefficient k 0 national renewable energy laboratory golden, colorado 80401 u. The float zone fz technique for crystal growth has been widely used since its first application to silicon in order to avoid container contamination. Francesca ferrazza, in practical handbook of photovoltaics second edition, 2012.
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 process was developed at bell labs by henry theuerer in 1955 as a modification of a method developed by william gardner pfann for germanium. Avoidance of the necessity of a containment vessel prevents. Float zone growth of silicon crystals using largearea seeding. The float zone method is the goto technique whenever a wafer requires highpurity silicon with little impurities.
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