Crystal-growing processes

The polycrystaUine EGS is converted to siagle-crystal silicon via the C2okralski (CZ) crystal growing process, based on the solidification of silicon atoms from the Hquid phase at a moving iaterface. Volume production of 200-mm diameter crystals is standard. Development of crystals having diameters of up to 400 mm has been predicted (3). 

Producing Junction Transistors. Junction transistors can be produced during the original crystal growing process for the silicon (or germanium) crystal by adding known n-type and petype impurities to the molten semiconductor as the solid crystal is slowly pulled from the melt. 

Since the advent of solid-state circuitry and miniaturized electronics, interest in ultramicroanalysis has grown tremendously, primarily with regard to contamination control and contaminant analysis. Exotic new materials which are being developed are often manufactured under clean-room envirorunents which must be tightly controlled and constantly monitored to ensure the integrity and consistency of the end product. For example, a mere trace of contaminant in a silicon crystal-growing process could jeopardize thousands of circuits. 

At equilibrium, crystal growth and dissolving rates become equal, and the process of Ostwald ripening may now appear, in which the larger crystals grow at the expense of the smaller ones. The kinetics of the process has been studied (see Ref. 103). 

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 crystal compositions vary, depending on the transport agent used, from TiB,4,y (Ij) and TiBj <,4 (TeCl4). At process temperatures > 1000°C and with I2, the transport direction is reversed. Crystals grow in the cold zone of the tube, but only microscopic needle-like crystals are obtained. ... 

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