Silicon single-crystal ingots

The silicon wafers used in conventional microelectronics arc fragile, relatively expensive, and their size is limited to that of the single-crystal ingot from which they are cut. In applications where large areas arc required, other materials seem... 

CVD is used in silicon production in two major areas 1) in the production of ultra-pure silicon from which single-crystal ingots are made, and 2) in the preparation of epitaxial and poly cry stalline films. 

Single-Crystal Silicon. Silicon is still the dominant material in photovoltaic. It has good efficiency, which is 25% in theory and 15% in actual practice. Silicon photovoltaic devices are made from wafers sliced from single crystal silicon ingots, produced in part by CVD (see Ch. 8, Sec. 5.1). However, silicon wafers are still costly, their size is limited, and they cannot be sliced to thicknesses less than 150 im. One crystalline silicon wafer yields only one solar cell, which has an output of only one watt. This means that such cells will always be expensive and can only be used where their high efficiency is essential and cost is not a major factor such as in a spacecraft applications. 

Elemental forms of gallium and arsenic, plus small quantities of dopant material — silicon, tellurium or chromium — are reacted at elevated temperatures to form ingots of doped single-crystal GaAs. 

Silicon is used in its monocrystalline form. The single crystal is developed by a variety of processes as a cylindrical ingot or boule. This cylindrical shape is ground to... 

To prepare single-crystal silicon ingots suitable for use as materials in semiconductors, the Czochralski method is used [8]. Polycrystalline silicon is melted in a crucible at 1400-1500°C under an argon atmosphere. Tiny... 

Silicon is used in its monocrystaUine form. The single crystal is developed by a variety of processes, as a cylindrical ingot, or boule. This cylindrical shape is ground to a nominal diameter and then shced. The resultant wafers are polished. Silicon crystallizes with a diamond structure. The wafers may have the (100), (110), or (111) orientation the (100) orientation is most commonly used. Figure 3.3 shows the layers in a cubic crystal system, described by their Miller indices, (6). The most important properties are given in Table 3.2. 

---