Czochralski growth process

Modeling of Czochralski growth process has a rich history [14-20]. First computations were done assuming the melt flow to be laminar, steady and axisymmetric ... 

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-... 

The substrate for this CVD process is a thin silicon rod, called a slim rod, which serves as a nucleation site for the depositing silicon. After deposition, the EGS, or polysilicon, is processed in the Czochralski (CZ) growth process. 

Process Stability and Control. Operationally, automatic control of the crystal radius by varying either the input power to the heater or the crystal pull rate has been necessary for the reproducible growth of crystals with constant radius. Techniques for automatic diameter control have been used since the establishment of Czochralski growth. Optical imaging of the crystal or direct measurement of the crystal weight has been used to determine the instantaneous radius. Hurle (156) reviewed the techniques currently used for sensing the radius. Bardsley et al. (157,158) described control based on the measurement of the crystal weight. 

A. Liidge, H. Riemann, M. Wiinscher, G. Behr, W. Loser, A. Croll, A. Muiznieks, in T. Duffar (ED) Crystal Growth Processes Based on Capillarity Czochralski, floating zone, shaping and crucible techniques (Chapter 4), John Wiley Sons, Chichester, England (in print)... 

E.M. Nunes et al., A volume radiation heat transfer model for Czochralski crystal growth processes. J. Cryst. Growth 236(4), 596-608 (2002). 

Briefly describe how ruby could be produced by the Czochralski (Cz) process. Under what situations, if any, would it be preferable to use the Cz process rather than the Verneuil process for ruby growth ... 

Silicon is produced by a well-controlled Czochralski crystal growth process in a very clean environment, that is, class of 1 or 10. In this process, a small seed crystal is dipped into a highly purified silicon melt. This seed is slowly pulled while the crucible containing the melt is rotated. The silicon crystal grows along the selected orientation of the seed to the rod. A cylindrical crystal is obtained from which slices are cut. This is followed by the atomic polishing phase. The side of one cubic face is 5.43A. The mechanical, electrical, and thermal properties of silicon have been presented in Table 10.1. 

N. V. Abrosimov, V. N. Kurlov, and S. N. Rossolenko, 2003, Automated control of Czochralski and shaped crystal growth processes using weighing techniques . Prog. Cryst. Growth Charact. 46, 1-57. 

Figure 4.21 A schematic diagram of the Czochralski crystal growth process. A seed crystal mounted on a cooled chuck is lowered into a molten bath, which will solidify to start crystal growth. This seed is then withdrawn slowly and new crystal grows on the existing seed. If the seed is a single crystal then with proper care the boule will also be a single crystal with zero dislocations. The diameter of the boule is adjusted by control of the shape of the meniscus of the liquid and the shape of the solidification boundary.

The liquid-encapsulated Czochralski process and the growth of III-V crystals... 

Meniscus-Defined Crystal Growth Systems. In most conventional meniscus-defined growth systems, a seed crystal is dipped into a pool of melt, and the thermal environment is varied so that a crystal grows from the seed as it is pulled slowly out of the pool. Two examples of meniscus-defined growth are shown in Figure 1. The Czochralski (CZ) method (Figure lb) and the closely related liquid-encapsulated Czochralski (LEC) method are batchwise processes in which the crystal is pulled from a crucible with... 

Figure 3. Streamlines (on right) and isotherms (on left) for growth of Si in a prototype Czochralski system. The volume of the melt, at the bottom in each drawing, changes among the calculations, affecting the qualitative form of the convection cell and the shape of the crystal interface. From Theory of Transport Processes in Single Crystal Growth from the Melt, by R. A. Brown, AIChE Journal, Vol. 34, No. 6, pp. 881 -911, 1988 [29]. Reproduced by permission of the American Institute of Chemical Engineers copyright 1988 AIChE.

The next step is to produce nearly perfect single-crystal boules of silicon from the ultrapure polycrystalline silicon. Many techniques have been developed to accomplish this, and they all rely on a similar set of concepts that describe the transport process, thermodynamically controlled solubility, and kinetics [8]. Three important methods are the vertical Bridgman-Stockbarger, Czochralski, and floating zone processes, fully described in Fundamentals of Crystal Growth by Rosenberger [9]. 

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