Appendix B Glossary

Actuator: Causes mechanical force or motion in Doping: Adding to a semiconducting material response to an electrical signal. small amounts of other elements (dopants) to change its electronic properties. Analog: Refers to electrical signals that can vary continuously over a range, as compared to Dynamic Random Access Memory (DRAM): The digital signals, which are restricted to a pair most common type of computer memory. of nominally discrete values. DRAM architecture usually uses one transis- Angstrom: One tenth of a nanometer, 10-10 tor and a capacitor to represent a bit, which is meters. a memory cell in a computer. Architecture: The overall logic structure of a Electron Cyclotron Resonance (ECR): A technol- computer or computer-based system. ogy that uses a high-frequency microwave en- ergy source to create a plasma in a confined Capacitor: Passive circuit element that stores region using a magnetic field for the purpose electrical charge, creating a voltage differen- of etching and deposition. tial. Capacitors can be fabricated within inte- grated circuits, as well as in the form of dis- Etching: A process in which chemicals are used crete components. to remove previously defined portions of the silicon oxide layer covering the wafer to ex- Charge-Coupled Devices (CCD): A type of solid- pose the silicon underneath. state electronic device used as a sensor in some types of cameras. Flat Panel Displays: A thin display screen that uses any of a number of technologies, such as Circuit Board: A card or board of insulating liquid crystal display. Flat panel displays are material on which components such as semi- used in laptop computers in order to keep the conductor devices, capacitors, and switches overall size and weight of the machine to a are installed. minimum. Clock An electronic circuit, often an integrated Gallium Arsenide (GaAs): A compound semi- circuit, that produces high-frequency timing conductor with properties necessary for very signals. A common application is synchroni- high-frequency microwave (analog) devices zation of the operations performed by a com- and optoelectronics. puter or microprocessor-based system. Typi- cal clock rates in microprocessor circuits are Gate: A simple electronic circuit that can imple- in the megahertz range, 1 megahertz equaling ment a specified logical operation. In essence, 10 6 cycles per second. gates act like switches. Computer processing units depend on large assemblies of gates, as Compact Disk (CD): An optical storage medium do integrated circuit memory chips. used for music and for computer data, among others. Integrated Circuit (IC): Electronic circuits, in- cluding transistors, resistors, capacitors, and ‘ Deposition: An operation by which a film is their interconnections, fabricated on a single placed on a surface. small piece of semiconductor material (chip). Die Bonder: Assembly equipment that bonds the Categories of ICs such as LSI and VLSI refer back side of an integrated circuit die to vari- to the level of integration, which denotes the ous materials. A die is a small piece of silicon number of transistors on a chip. ICs may be wafer that contains the complete circuit being digital (logic chips, memory chips, or micro- manufactured. processors) or analog.

-43- 44. Miniaturization Technologies

Ion Implantation: A process in which silicon is Microprocessor: A computer central processing bombarded with high-voltage ions in order to unit on a single chip. implant them in specific locations and pro- Nanometer: One-billionth of a meter. vide the appropriate electronic characteris- tics. Optical Disks: Recording media including CDs that store information in patterns of micro- Liquid Crystal Display (LCD): A liquid crystal scopic pits on the surface of the disk, which display is a technique that uses a transistor can then be detected by a solid state laser and for each monochrome or each red, green and detector system and reproduced as sound, blue dot. It provides sharp contrast and images, or data. speeds screen refresh. LCD technology is commonly used in digital watches and laptop Optoelectronic Devices: Devices that convert computers. light signals to electronic signals and vice versa. Lithography A process in which the desired cir- cuit pattern is projected onto a photoresist RAM (Random Access Memory): Most common- coating covering a silicon wafer. When devel- ly, an integrated circuit that stores data in oped, portions of the resist can be selectively such form that it can be read, erased, and removed with a solvent, exposing parts of the rewritten under the control of a computer wafer for etching and diffusion. processor. Any memory location in a RAM can be addressed directly (random access) as Logic Chips: ICs that manipulate digital data. opposed to sequentially or serially. LSI: Large-scale integration. Typically involving between 2,000 and 64,000 transistors. Resist, Photoresist: Chemicals used in litho- graphic processing of integrated circuits Mainframe Computer: A system, normally in- which, much like photographic emulsions, tended for general-purpose data processing, can be exposed by light, X-rays, or other radi- characterized by high performance and ver- ation to form patterns. satility. Mainframes have grown steadily in capability as smaller and less expensive ma- Semiconductors: Materials, e.g., silicon, that chines have progressed. have four electrons in their outer electron shells and have electrical conductivities that Mask: Stencil-like grid used in creating litho- are lower than good conductors such as met- graphic patterns on semiconductor chips. als but higher than insulators such as glass. Mass Storage: Refers to peripheral equipment Other semiconductors include germanium, for computer memory suitable for large gallium arsenide (GaAs), iridium phosphide (InP), mercury telluride(HgTe), cadmium tel- amounts of data or for archival storage. Typi- luride (CdTe), and alloys of these compound cal mass storage devices are disk and tape drives. semiconductors. Memory Chips: Devices for storing information Sensor: Converts a pressure, temperature, or oth- in the form of electronic signals. er physical parameter into an electrical sig- nal, often for use in a control system. A digital Microcomputer: Refers to integrated circuits speedometer for an automobile transforms that contain a microprocessing unit plus the output of a sensor into a miles-per-hour memory, as well as to computers designed reading, as does an airplane’s air speed indi- around microprocessors or single-chip mi- cator. In the case of the automobile speedom- crocomputers. eter, rotary motion is converted into an elec- trical signal, while an air speed indicator Micrometer: One-millionth of a meter. depends on the pressure created by the mo- Micron: One-millionth of a meter. tion of the airplane. Appendix B-Glossary .45

Silicon: One of the most common elements found Wafer: A thin disk, cut from silicon or other semi- in nature and the basic material used to make conductor material. The wafer is the base the majority of semiconductor wafers. material on which integrated circuits are fab- Stepper: A sophisticated piece of equipment ricated. It is typically 4 to 8 inches in diame- used to transfer an integrated circuit pattern ter. from a mask onto a wafer. Yield: In the production of microelectronic de- Substrate: A piece of material, typically a semi- vices, the fraction that survive all tests and conductor, on which layers of materials are inspection, function correctly, and can be deposited and etched to fabricate a device or sold or incorporated into the manufacturer’s a circuit. own end products. Production costs depend Transistor: An electronic device that can be used heavily on yields, which themselves depend to switch or amplify electronic signals. on circuit design, fabrication equipment, and VLSI: Very large-scale integration. Typically in- control of the manufacturing process. volving more than 64,000 transistors.