An introduction to Semiconductors
2008-08-20

                                                                                                 An introduction to Semiconductors       While polymers are highly visible engineering materials with a major impact on contemporary society, semiconductors are relatively invisible but have a monumental social impact.       A semiconductor is a substance, usually a solid chemical element or compound that can conduct electricity under some conditions but not others, making it a good medium for the control of electrical current.       The specific properties of a semiconductor depend on the impurities, or dopants, added to it. An N-type semiconductor carries current mainly in the form of negatively-charged electrons, in a manner similar to the conduction of current in a wire. A P-type semiconductor carries current predominantly as electron deficiencies called holes. A hole has a positive electric charge, equal and opposite to the charge on an electron. In a semiconductor material, the flow of holes occurs in a direction opposite to the flow of electrons.       Elemental semiconductors include antimony, arsenic, boron, carbon, germanium, selenium, silicon, sulfur, and tellurium. Silicon is the best-known of these, forming the basis of most integrated circuits (ICs). Common semiconductor compounds include gallium arsenide, indium antimonite, and the oxides of most metals. Of these, gallium arsenide is widely used in low-noise, high-gain, and weak-signal amplifying devices.       Semiconductors have a wide range uses in many different areas. Semiconductor devices are all around us. They can be found in just about every commercial product we touch, from the family car to the pocket calculator. Semiconductor devices are contained in television sets, portable radios, stereo equipment, and much more.       Science and industry also rely heavily on semiconductor devices. Research laboratories use these devices in all sorts of electronic instruments to perform tests, measurements, and numerous other experimental tasks. Industrial control systems (such as those used to manufacture automobiles) and automatic telephone exchanges also use semiconductors. Even today heavy-duty versions of the solid-state rectifier diode are being use to convert large amounts of power for electric railroads. Of the many different applications for solid-state devices, space systems, computers, and data processing equipment are some of the largest consumers.       The various types of modem military equipment are literally loaded with semiconductor devices. Many radars, communication, and airborne equipment are transistorized. Data display systems, data processing units, computers, and aircraft guidance-control assemblies are also good examples of electronic equipments that use semiconductor devices. All of the specific applications of semiconductor devices would make a long impressive list.       The fact is semiconductors are being used extensively in commercial products, industry, and the military.       The semiconductor industry has experienced exceptional double-digit growth over the past 25 years, fueled by strong demand in end-use markets such as computing, communications, consumer appliances, and industrial applications. Its future, however, depends on the ability of semiconductor manufacturers and equipment suppliers alike to lower cost while pushing the technological limits of lithography, materials science, and further the development of new manufacturing techniques like dual damascene. As well as highlight areas where equipment productivity has added, and can continue to add, tremendous value to the growth of the industry. a new paradigm called Process Module Systems should be put forth to address the increasingly complex manufacturing requirements as well as economic challenges that the industry, as a whole, faces.