Pulling, crystal growth

Figure 1. Schematic diagram of the cold metal crucible system used for synthesis, zone melting and crystal pulling crystal growth (from ref. 5).

Crystal Growth of Borides e.7.4.2. Liquid-Phase Methods 6.7.4.2.1. Crystal Pulling. 

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. 

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... 

Another attempt to make feed rods for FZ crystal growth from cheap starting material is to melt solar (or lower) grade raw silicon in a quartz crucible and pull a rod of the desired diameter after the CZ method, not necessarily a single crystal. A lot of impurities can be removed by segregation and in the subsequent FZ step, almost all oxygen and most of the other impurities can be removed, too. However, the actual costs of such an approach must be carefully considered, but it is still an option to overcome the diameter limitations of the Siemens process. 

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