Electrical conductivity of silicon

Even though silicon is metallic in appearance, it is not generally classified as a metal. The electrical conductivity of silicon is so much less than that of ordinary metals it is called a semiconductor. Silicon is an example of a network solid (see Figure 20-1)—it has the same atomic arrangement that occurs in diamond. Each silicon atom is surrounded by, and covalently bonded to, four other silicon atoms. Thus, the silicon crystal can be regarded as one giant molecule. 

Fortuitously, the good electrical conductivity of silicon prevents these charges from building up to dangerous levels, which explains why the reported pattern placement errors due to such hypothesized deflections have been smaller than measurement capability (20 nm). Another method for minimizing charging... 

The increasing importance of multilevel interconnection systems and surface passivation in integrated circuit fabrication has stimulated interest in polyimide films for application in silicon device processing both as multilevel insulators and overcoat layers. The ability of polyimide films to planarize stepped device geometries, as well as their thermal and chemical inertness have been previously reported, as have various physical and electrical parameters related to circuit stability and reliability in use (1, 3). This paper focuses on three aspects of the electrical conductivity of polyimide (PI) films prepared from Hitachi and DuPont resins, indicating implications of each conductivity component for device reliability. The three forms of polyimide conductivity considered here are bulk electronic ionic, associated with intentional sodium contamination and surface or interface conductance. 

Anthracite is calcined at appreciably higher temperatures (1800—2000°C). The higher calcining temperatures for anthracite are necessary to complete most of the shrinkage and to increase the electrical conductivity of the product for use in either Soderberg or prebaked carbon electrodes for aluminum, silicon, or phosphoms manufacture. 

The electrical conductivity of a semiconductor lies between that of an insulator and a well conducting material. For a further examination of the conduction, our starting points are silicon and germanium. Both elements have the cubic shape of a diamond structure, as shown in figure 11.4.5. 

A new solid state chemical sensor for sulfur dioxide utilizing a sodium sulfate/rare earth sulfates/silicon dioxide electrolyte has been developed. The addition of rare earth sulfates and silicon dioxide to the sodium sulfate electrolyte was found to enhance the durability and electrical conductivity of the electrolyte. The electrolyte exhibits a Nernstian response in the range of SC gas concentrations from 30 ppm to 1 %. 

In Figure 1, the electrical conductivities of several coimnon substances and representative solid electrolytes are shown at the temperature where the materials have potential application. The solid electrolytes have conductivities that fall between those of a typical semiconductor, silicon, and a typical aqueous electrolyte, sodium chloride. 

The small conductivity of silicon can be enhanced at normal temperatures if the silicon crystal is doped with certain other elements. For example, when a small fraction of silicon atoms is replaced by arsenic atoms, each having one more valence electron than silicon, extra electrons become available for conduction, as shown in Fig. 16.32(a). This produces an n-type semiconductor, a substance whose conductivity is increased by doping it with atoms having more valence electrons than the atoms in the host crystal. These extra electrons lie close in energy to the conduction bands and can easily be excited into these levels, where they can conduct an electric current [see Fig. 16.33(a)). 

Arsine is used commercially by the electronics industry for epitaxial growth of gallium arsenide and as a dopant applied to ultrapure crystals to increase electrical conductivity for silicon-based electronic devices. 

Figure 5. Temperature dependence of electrical conductivity of arc-melted silicon borides before and after heat-treatment at 1673K for 0.5hr.

The electrical conductivity of a semiconductor such as silicon can be increased by a process known as doping. Doping is the addition of a small amount of another element to a ... 

How can the electrical conductivity of a semiconductor such as silicon be increased ... 

The relatively good electrical conductivities of metals are due almost entirely to the presence of the free electrons in the electron cloud. They can be caused to move, i.e. an electric current can be made to flow, by the application of much less energy—i.e. a louver electromotive force—than would be needed to bring about actual separation of the electrons from their outer orbits. Electrical insulators have crystal lattices in which there are no free electrons. Thus, for example, in fused silica all the valency electrons are tied up in holding the silicon and oxygen atoms together. Here we have an explanation of the fact that the electrical conductivity of the metal copper is about 1024 times greater than that of the insulator fused silica. 

---