Ab Initio - from first principles. An ab initio calculation is a calculation derived from first principles.
Aberrations - failure of a mirror or lens to produce an exact point-to-point correspondence between an object and an image of the object.
Acceptor - group three elements in the periodic table such as boron, B, aluminum, Al, gallium, Ga, or indium, In, have one less electron in the outer most energy level than silicon, Si. When these atoms are introduced into silicon, an impurity level is created near the valence band. At zero degrees kelvin the impurity level is empty, at room temperature sufficient energy is available to excite electrons from the valence band into the impurity level. Because these Elements introduce impurity levels that accept electrons, they are referred to as acceptors. See also donor.
Acetic Acid - chemical formula CH3COOH, a carboxylic acid, acetic acid is a relatively weak acid mainly used as a pH buffer. Acetic acid is commonly sold as a 100% solution and has a density of 1.05Kg/L.
Acetone - chemical formula CH3COCH3, acetone is a flammable solvent used primarily to clean-up positive photoresist. Acetone is commonly sold as a 100% solution and has a density of 0.79Kg/L. Skin contact and breathing acetone vapor should be avoided.
Acid - substance that ionizes in water to produce H+ Ions. Acid solutions have H+ concentrations >1x10-7 (pH < 7). See also alkali or base.
Acoustic Streaming - localized high velocity streams of fluid created by high frequency sound in a liquid.
Actinism - property of radiant energy that produces chemical changes, particularly in the visible and ultraviolet spectrum.
Active Component - circuit element that switches the flow of current or has gain. Example are: transistors, diodes, vacuum tubes, etc.
Air Change - volume of air recirculating through a cleanroom per minute divided by the volume of the room. Generally the lower the cleanroom class the higher the air changes. A class 1000, class 100, class 10 and class 1, Cleanroom should have 5-6, 7, 7-10, and 10 air changes per minute respectively.
Algorithm - technique or method of performing a mathematical calculation. An algorithm will typically have a finite number of steps that are repeated to perform a calculation.
Alignment - act of moving a mask or reticle to match up alignment marks. Alignment insures that a new pattern being added to a wafer is aligned to the previous pattern or patterns on the wafer.
Alignment Mark - mark or target on a reticle or mask that is used to achieve alignment. For example, a wafer might have a cross printed on it from a previous layer, and a reticle might have a cross designed to fit inside the cross already on the wafer. When the smaller cross fits within the larger cross, the reticle is aligned to the wafer.
Alkali - acid neutralizing substance. A soluble salt with base properties..
Alkali Metal - family of group IA metals in the periodic table made up of, lithium, Li, sodium, Na, potassium, K, rubidium, Rb, cesium, Cs, and francium, Fr, all group IA elements except hydrogen, H. The oxides and hydroxides of these metals are strong bases. See also, alkali.
Alkaline - having the properties of an alkali, specifically acting as a base.
Alkaline Earth - family of group IIA elements, beryllium, Be, magnesium, Mg, calcium, Ca, strontium, Sr, barium, Ba, and radium, Ra. The oxides and hydroxides of these elements are strong bases. See also, alkaline.
Alloy - process of "alloying" two or more substances together. An alloy is a combination of two or more elements where at least one element is a metal.
ALSTTL - Advanced LSTTL. A fast bipolar IC process with power dissipation approximately one half of LSTTL.
Alternating Current - electrical current that reverses direction at regular intervals, for example 60 Hertz in the U.S.
Aluminum - atomic symbol, Al, aluminum is the 13th element in the periodic table (atomic number 13) with an atomic weight of 26.98, aluminum is a metal, an excellent conductor with a resistivity of approximately 2.8µohm-cm, and is commonly used as an interconnect in integrated circuits and sometimes as a P-type dopant due to it's high diffusivity in silicon. Aluminum is commonly deposited by evaporation or sputtering.
Aluminum Etch - etching solution used to etch aluminum. Typically aluminum etches are based on phosphoric acid. A common aluminum etch formula would be phosphoric acid, H3PO4, 80ml, nitric acid, HNO3, 5ml, and water, H2O, 15ml acetic acid, CH3COOH, will sometimes be added as a buffer. Aluminum etches evolve hydrogen bubbles that may cling to the aluminum layer being etched locally preventing etching, and leaving behind aluminum residue, "snow". Some mechanism such as agitation or low pressure must be supplied to remove hydrogen bubbles. Surfactants may also be used to enhance wetting.
Ammonia - chemical formula NH3, ammonia is a toxic gas with a TLV of 25ppm, and is combustible in the range of 12-28%. Ammonia has a strong pungent odor and is irritating to lungs, skin and eyes. Ammonia is commonly used as a deposition gas for silicon nitride, Si3N4 and may also be used to anneal titanium, Ti, to form titanium nitride, TiN or to anneal gate oxides to form oxynitride, SixOyNz.
Ammonium Fluoride - chemical Formula NH3F, ammonium fluoride is a toxic, corrosive chemical used to buffer hydrofluoric acid, HF, in buffered oxide etch, BOE. Fluorine is not only toxic but may be absorbed through the skin without immediate evidence of irritation and later react with the calcium in bones and or poison the person exposed to the chemical. Ammonium fluoride is commonly sold as a 40% solution with a density of 1.11Kg/L.
Ammonium Hydroxide - chemical formula NH4OH, ammonium hydroxide is a corrosive chemical with a strong ammonia odor. Ammonium hydroxide fumes are irritating to lungs, skin and eyes. Ammonium hydroxide is used in SC1 cleaning solutions and is commonly sold as a 30% solution with a density of 0.90Kg/L.
Amorphous - a material state where the atoms making up the material are randomly oriented relative to each other. See also crystalline, polycrystalline.
Ampere - a measure of electric current flow. The ampere is defined as the transfer of one coulomb per second
Amplifier - a device that increases the amplitude of a signal. Ideally an amplifier will increase amplitude without changing any other aspects of the signal being amplified.
Amplify - to increase the amplitude.
Amplitude - the maximum departure of a time varying signal or oscillation from the average value.
Analog - a signal in an electrical circuit that can have a continuous range of values. See also, digital.
AND - a flash memory architecture that uses Fowler Nordheim tunneling to achieve low power programming.
AND Gate - a basic logic gate that outputs a 1 only if both inputs are a 1 , otherwise outputs a 0. See also, NAND, NOR and OR.
Angle of Incidence - the angle between a ray of light incident on a surface and a line drawn normal to the surface.
Angle of Reflection - the angle between a ray of light reflected from a surface and a line drawn normal to the surface. From Snell's law the angle of incidence is equal to the angle of reflection.
Angstrom - 1 x10-10 meters, 1/10 nanometer.
Anion - a negatively charged ion, i.e., an ion that migrates to the anode in an electrolyzed solution.
Anisotropic - different in one direction than in another direction or directions. An anisotropic etch process is an etch process that has a higher etch rate in one direction than other directions, or an anisotropic medium is a medium where some property or properties depend on the direction in which the medium is measured. See also, isotropic.
Anneal - a heating and cooling process designed to reduce stress.
Application Specific Integrated Circuit(ASIC) - a proprietary integrated circuit designed to meet a particular customers specific application requirements.
Application Specific Standard Product(ASSP) - typically an ASIC that has been converted into a standard product. See also, application specific integrated circuit.
Argon - atomic symbol, Ar, argon is the 18th element in the periodic table (atomic number 18) with an atomic weight of 39.95. Argon is a group 0 element and is inert. Argon is used as inert gas for annealing and as a background gas in sputtering due to it's relatively high ionization cross section. Argon is an asphyxiant.
Argon Fluoride Laser - in the semiconductor industry, generally used to refer to an excimer laser that uses argon and fluorine gases to produce an output of 193 nanometers. Expected to be the light source of choice for critical levels at 90nm and 65nm minimum linewidths.
Array - a group of items that are arranged in rows and columns. For example a memory array would be a group of memory cells arranged in rows and columns.
Arsenic - atomic symbol, As, arsenic is the 33rd element in the periodic table (atomic number 33) with an atomic weight of 74.9. Arsenic is a group V element making it a donor in silicon, i.e., makes silicon N-type. Arsenic has the same atomic diameter as silicon and so introduces very little strain into a silicon crystal lattice. Arsenic has a relatively low diffusivity and is widely used to create shallow doped junctions such as source/drains. Arsenic is toxic and carcinogenic.
Arsine - chemical formula AsH3, arsine is a highly toxic gas with a garlic like odor and a TLV of 0.05ppm. Arsine is flammable in the range of 4.5 - 78%. Arsine is so toxic that is has been used as a chemical warfare agent. Arsine is used as a dopant gas during various CVD reactions and to create As+ ions for ion implantation.
Ashing - the process of removing photoresist using an oxygen plasma or ultraviolet light generated ozone. Ashing produces no chemical waste, photoresist is volatilized into N2, O2, CO and CO2 gases.
Aspect Ratio - the depth or height of a feature divided by the width of the feature. A high aspect ratio indicates a feature is narrow relative to it's height or depth. Example high aspect ratio features would be, contacts that are narrow relative to their depth, trenches that are narrow relative to their depth or metal lines that are tall relative to their width.
Aspheric Surface - a lens or mirror surface that has been altered from spherical in order to reduce optical aberrations.
Asphyxiant - a gas that causes unconsciousness or death through lack of oxygen (suffocation).
Assembly - the process of packaging semiconductor die.
Atom - the smallest particle that can exist and still exhibit the properties of an element.
Atomic Layer Deposition - a deposition technique whereby pulses of gaseous reactants are used to deposit a film one layer at a time. See tech brief on Atomic Layer Deposition.
Atomic Number - the number of protons and electrons in an atom of a specific element in the ground state.
Atomic Percent - the number of atoms of an element per unit volume divided by the number of atoms per unit volume of the substance containing the element.
Atomic Symbol - a standard chemical abbreviation used to indicate a specific element.
Atomic Weight - the weight of an atom of a specific element where one atomic weight unit is defined as the weight of 1/12 of a carbon 12 Atom.
Atmospheric Pressure - the pressure exerted by the weight of air. The standard atmospheric pressure on earth is 14.7 pounds per square inch (PSI) or 1 kilogram (Kg) per square centimeter (cm2). Actual pressure at any point and time on the face of the earth depends on altitude and atmospheric conditions.
Atmospheric Pressure Chemical Vapor Deposition - Chemical Vapor Deposition performed at atmospheric pressure.
Autodoping - dopant atoms out-gas from a wafer and are absorbed either at another location on the same wafer or on an adjacent wafer. The key concept is that autodoping is a form of contamination, doping results in undesired locations.
Automation - making a process automatic eliminating the need for human intervention.
