Single Czochralski

TJItrahigh (99.999 + %) purity tellurium is prepared by zone refining in a hydrogen or inert-gas atmosphere. Single crystals of tellurium, tellurium alloys, and metal teUurides are grown by the Bridgman and Czochralski methods (see Semiconductors). 

An example of an analysis done on polysilicon and single-crystal Czochralski silicon (CZ) is shown in Table 1. As can be seen, polysilicon, which was used to grow the crystal, is dirtier than the CZ silicon. This is expected, since segregation coefficients limit the incorporation of each element into the crystal boule during the crystal growth process. All values shown in the table are from bulk analysis. Table 2 shows NAA data obtained in an experiment where surface analysis was accom-... 

N. Miyazaki, S. Okuyama. Development of finite element computer program for dislocation density analysis of bulk semiconductor single crystals during Czochralski growth. J Cryst Growth 183 S, 1998. 

The next step is the hydrogen reduction of the trichlorosilane (Reaction 2 above). The end product is a poly crystalline silicon rod up to 200 mm in diameter and several meters in length. The resulting EGS material is extremely pure with less than 2 ppm of carbon and only a few ppb of boron and residual donors. The Czochralski pulling technique is used to prepare large single crystals of silicon, which are subsequently sliced into wafers for use in electronic devices.1 1... 

The Czochralski Method has remained the most frequently employed method for obtaining single crystals. The seemingly formidable complexities involved have been conquered by the use of computer-control of the crystal-growing Parameters. One such system, available commercially, is shown in 6.4.12. (on the next page). 

Czochralski seeded single-crystal growth from semiconductors stable as melts, which yields the meters-large single crystals of ultra-high purity silicon used in nearly all technological applications. 

Czrochralski A process for growing large single crystals. The bulk of the material is melted in a crucible. A single crystal of the same material is lowered onto the surface of the melt and then slowly pulled upward, producing a cylindrical single crystal known as a boule. Invented by J. Czochralski as a method for determining the velocity of crystallization of molten metals. 

Fig. 10. Pulling of a single crystal of UNi from the levitated melt by the Czochralski method...

FIGURE 3.14 (a) The Czochralski process for producing a very pure single crystal of silicon (b) silicon boule. (Photo courtesy of Tonie van Ringelestijn.)... 

Figure 2.1. Various forms exhibited by crystals, (a) Polyhedral crystals (b) hopper crystal (c) dendritic crystal (snow crystal, photographed by the late T. Kobayashi) (d) step pattern observed on a hematite crystal (0001) face (e) internal texture of a single crystal (diamond-cut stone, X-ray topograph taken by T.Yasuda) (f) synthetic single crystal boule. Si grown by the Czochralski method (g) synthetic corundum grown by the Verneuil method.

The Bridgman and Czochralski (LEG) methods as mentioned above, are useful for growing GaAs single crystals, from the viewpoint of practical applications. The following methods tried or proposed by many workers are... 

Purified polycrystalline CVD silicon from this reaction is then melted and a single-crystal boule weighing as much or more than 50 kg, and having a diameter up to 20 cm, is pulled from the melt by Czochralski growth (8). Metallurgical-grade silicon is not sufficiendy pure for applications in electronics... 

Overview of Unit Operations. To maximize the electron or hole (carrier) mobility and thus device speed, ICs are built in single-crystal substrates. Methods of bulk crystal growth are therefore needed. The most common of these methods are the Czochralski and float-zone techniques. The Czochralski technique is a crystal-pulling or melt-growth method, whereas the float-zone technique involves localized melting of a sintered bar of the material, followed by cooling and, thus, crystallization. 

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