Semiconductor devices Integrated Circuit Electronics

Berylha ceramic parts ate frequendy used in electronic and microelectronic apphcations requiting thermal dissipation (see Ceramics as ELECTRICAL materials). Berylha substrates are commonly metallized using refractory metallizations such as molybdenum—manganese or using evaporated films of chromium, titanium, and nickel—chromium alloys. Semiconductor devices and integrated circuits (qv) can be bonded by such metallization for removal of heat. 

Solid-state electronic devices such as diodes, transistors, and integrated circuits contain p-n junctions in which a p-type semiconductor is in contact with an n-type semiconductor (Fig. 3.47). The structure of a p-n junction allows an electric current to flow in only one direction. When the electrode attached to the p-type semiconductor has a negative charge, the holes in the p-type semiconductor are attracted to it, the electrons in the n-type semiconductor are attracted to the other (positive) electrode, and current does not flow. When the polarity is reversed, with the negative electrode attached to the n-type semiconductor, electrons flow from the n-type semiconductor through the p-type semiconductor toward the positive electrode. 

SACHEM Inc., located in Cleburne, Texas, is a producer of high-purity bulk chemicals for companies that have high-purity requirements in their chemical processing. As stated in Workplace Scene 1.2, one of their products is tetramethylammonium hydroxide (TMAH), which is sold to semiconductor industries. The analysis of TMAH for trace anions such as chloride, nitrate, nitrite, and carbonate is critical for SACHEM s quality control laboratory. If these ions are present on the integrated circuit boards manufactured by one of their semiconductor customers, they may cause corrosion severe enough to affect the functionality and performance of the electronic devices in which the circuit boards are used. In SACHEM s quality control laboratory, ion chromatography procedures have been developed to measure the anion concentrations in TMAH. Because the concentration levels are trace levels, a clean room environment, like that described in Workplace Scene 1.2, is used. A special procedure for carbonate analysis is required so that the absorption of carbon dioxide from the atmosphere can be minimized. 

Thin films (qv) of vitreous silica have been used extensively in semiconductor technology. These serve as insulating layers between conductor stripes and a semiconductor surface in integrated circuits, and as a surface passivation material in planar diodes, transistors, and injection lasers. They are also used for diffusion masking, as etchant surfaces, and for encapsulation and protection of completed electronic devices. Thin films serve an important function in multilayer conductor insulation technology where a variety of conducting paths are deposited in overlay patterns and insulating layers are required for separation. 

Solid-state electronic devices such as diodes, transistors, and integrated circuits contain p-n junctions in which a p-type semiconductor is in contact with an n-type semiconductor (Fig. 3.48). Because solar radiation can excite electrons into a conduction band, semiconductors can be used to generate an electrical current by the action of sunlight. 

Doped semiconductors are essential components in the modern solid-state electronic devices found in radios, television sets, pocket calculators, and computers. Devices such as transistors, which control electrical signals in these products, are made from M-type and p-type semiconductors. In modern integrated circuits, an amazing number of extremely small devices can be packed into a small space, thus decreasing the size and increasing the speed of electrical equipment. For example, computer microprocessors now contain up to 42 million transistors on a silicon chip with a surface area of about 2 cm2 and are able to execute as many as 1.5 billion instructions per second. 

A triode is made from two closely situated pn junctions. These devices are also known as transistors, which is a circuit element that is useful for amplifying or switching currents. Solid-state transistors have revolutionized the electronics industry. Today, very complicated integrated circuits can be made of thousands of semiconductor elements, all contained in a very small package. Such integrated circuitry is vital to the computer, as well as scientific, telecommunication, and many other businesses. Our age is truly the age of the semiconductor ... 

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