GLOSSARY

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ABSORPTION The process which involves the penetration of a gas or vapor into the bulk of a solid or liquid, usually by some type of diffusion and its subsequent binding or capture; “taking in”.

ADHESION The atomic or molecular attraction acting at the surfaces of two materials in contact. It commonly occurs between a film and a substrate or between films in multilayer coatings.

ADSORPTION The process by which gas or vapor is bonded on a solid or liquid surface; “sticking”.

AES Auger Electron Spectrometry

AMORPHOUS Usually refers to a particle or grain size smaller than 30 Å that does not show crystal structure when using X-ray diffraction techniques. A film structure which is without long-range crystallographic order.

ANGLE OF INCIDENCE The angle between the predominant direction at which electro-magnetic radiation and/or particles are incident on a substrate and the normal to the substrate surface.

ANNEAL A vacuum heat treatment of a material which relaxes or homogenizes uneven or heterogeneous regions in a substrate which are present as a result of internal stress; variations of composition or phase, or other structural or thermodynamic differences.

ANODE The positive electrode in an electron device. The most positive electrode in an ion pump. This electrode may collect electrons and negative ions.

ATOMIC MASS UNIT A unit of mass equal to one-twelfth of a neutral carbon atom having six protons and six neutrons (12 carbon); equivalent to 1.660566(E-27) kg. Abbreviated - amu.

AUGER MASS UNIT A surface analysis technique which observes the energy of secondary electrons ejected by an Auger emission mechanism from a sample bombarded with electrons (in the energy range of 100 eV to a few keV).

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BACKSTREAMING The movement of the vapor of a pump’s working fluid in the direction of the region being evacuated.

BAFFLE A system of cold surfaces placed between the inlet of a pump and the region on which it is pumping to condense backstreaming vapor and return it to the pump.

BAKE-OUT The heating of vacuum system components during the pumping process for the purpose of degassing; accelerates the evolution of adsorbed and absorbed gases.

BASEPLATE A plate which supports a bell jar and enclosed materials or components subjected to vacuum, providing mechanical, electrical and other connections to apparatus within the vacuum system.

BEAM DENSITY Describes what is scientifically the power density of an electron beam striking a target to be melted or evaporated.

BELL JAR A cylindrical vacuum chamber with a removable seal supported by a baseplate.

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CATHODE The negative electrode in an electron device. The most negative electrode in an ion pump. This electrode may emit electrons and collect positive ions.

CHEMICAL VAPOR A deposition process in which the vaporization of DEPOSITION (CVD) volatile compound of the substance to be deposited is followed by a reaction of this compound with other gases, vapors, or liquids at the substrate surface or by thermal decomposition of the compound. The result is the deposition of nonvolatile reaction product on the substrate surface. This is versatile deposition technique which can utilize a variety of chemical reactions for the deposition of metals, semiconductors and insulators.

COLD-CATHODE An ionization gauge in which electrons are released IONIZATION GAUGE from the cathode by photon and ion bombardment at ambient temperature, and for which thermionic emission can be neglected.

COMPOUND Two or more elements combined chemically in specific proportions.

CONDENSATION The physical process by which a vapor becomes a liquid or solid.

CONDUCTANCE The ration of throughput, under steady-state conservative conditions, to the pressure differential between two specified cross sections inside a pumping system.

CROSS-OVER PRESSURE The pressure at which pumping is transferred from one pump to another that can produce a higher speed and/or a lower pressure.

CRYOGENIC PUMP A vacuum pump which operates by the CRYOPUMP condensation and/or sorption of gas at surfaces maintained at temperatures sufficiently low for the vapor pressures of the condensed gases to be insignificant.

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DARK SPACE Loosely applied to the Faraday Dark Space which occurs between a cathode and plasma in a glow discharge.

DEGASSING The deliberate removal of gas from a material, often achieved by heating the material under vacuum.

DIELECTRIC Non-conducting; insulator; charge storage as a capacitor.

DIFFUSION A mixing together of the molecules of gases or liquids by spreading into one another; migration.

DIFFUSION PUMP A vapor pump in which the pumped gas flows into a vapor stream under conditions in which molecular flow predominates. Momentum is transferred from the vapor to the gas carrying it along in the direction of the stream. Pump fluid is heated in vacuum to generate the vapor which is directed through a nozzle. It expands freely in the stream before reaching a cool wall where it condenses and is returned to the boiler to begin a new cycle.

DISSOCIATE The process whereby a chemical compound is broken down into its constituents on a temporary and reversible basis.

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EJECTOR PUMP A vapor pump in which the pumped gas enters the pump and the vapor stream under predominantly viscous flow conditions.

ELECTRODE An electrically conducting element of an electron device, usually connected to an external electric circuit, which emits, collects, or influences the flow of the current in the device.

ELECTRON Elementary particle bearing a negative charge and a mass approximately 1/1840 of a hydrogen atom.

ELECTRON BEAM A stream of electrons moving with about the same velocity and in the same direction, forming a beam.

ELEMENT A Substance entirely consisting of atoms having the same atomic number.

EPITAXY A growth of one substance upon another. The crystal structure of the substrate is copied by the growing substance and substituted for its natural structure.

ESCA Electron Spectroscopy for Chemical Analysis.

ETCHING The removal of material from a surface.

EVAPORATION The conversion of a substance from the liquid state into the gaseous state by heating.

EVAPORATION, 1: An evaporation technique utilizing a resistively FILAMENT heated filament, usually composed of refractory metal wire or foil, for evaporating a source material which has been previously applied to the filament.

2: A deposition technique utilizing a resistively heated filament composed of the source material itself to produce sublimation of the source. This technique is primarily applicable to vapor sources having high vapor pressures at temperatures below the melting temperature and which are consequently able to vaporize from the solid phase.

EVAPORATION, FLASH An evaporation technique which involves the continuous feeding of very small quantities of a premixed powder/pellets/wire of the constituents onto the surface of a filament or of a crucible having sufficient heat capacity and being sufficiently high temperature to cause instantaneous evaporation of all components independent of their vapor pressure.

EXOTHERMIC Usually applied to a chemical reaction in which energy in the form of heat is evolved.

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FEEDTHROUGH; A device for transmitting electrical current, fluids or FEEDTHRU mechanical motion through the walls of a vacuum system; pass-through.

FEM Field Electron Microscopy.

FILM A planar structure of a solid built up on a substrate by an atomic or molecular process involving the use of controllable deposition methods. The terms thin and thick films are arbitrarily used at times to indicate the geometrical thickness of <1µm or 1µm, respectively.

FIM Field Ion Microscopy.

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GAS A state of matter in which the molecules move freely to occupy the total volume of an enclosure.

GETTER A material which reacts readily with active gases to form stable low vapor pressure chemical compounds, so as to remove these gases from the gas phase.

GRAIN BOUNDARY Metallurgy term that describes the region between two crystals of different orientation in a solid body.

GRAIN SIZE The size of a grain in a solid. Sophisticated methods and statistics are used for asymmetric grain measurement.

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HOT CATHODE An ionization gauge in which pressure is measured IONIZATION GAUGE in terms of the current of positive ions produced by electrons emitted form a heated cathode.

HOT FILAMENT An envelope which contains a hot cathode ionization IONIZATION GAUGE TUBE gauge and tubulation which can be connected to a vacuum system.

HYSTERESIS In electromagnetic and elastic technology, descries a property such as magnetism or strain remaining after removal of the force causing that effect.

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IMPEDANCE The apparent resistance in an alternating current circuit, made up of two components, reactance and true or ohmic resistance; the reciprocal of conductance.

INDUCTANCE The effect on induced magnetic filed produced by current flowing has on the magnitude of that current.

ION An atom or molecule having attained one or more units of electrical charge due to loss or gain of electrons.

ION IMPLANTATION A process by which atomic species are ionized and accelerated towards a surface of a solid with sufficient kinetic energy so that they became entrapped in that solid after impingement.

ION PUMP An electron device in which ionization produces a significant rate of gas removal. The ion pump is a “capture and hold” type of pump.

IONIZATION A process which results in the formation of ions. Such a process can occur by adding (or removing) one or more electrons to (or from) an atom (or molecule).

IONIZATION GAUGE A vacuum gauge comprising a means of ionizing the gas and a means of correlating the ion current to the collector with the pressure of the gas.

ISS Ion Scattering Spectrometry. KINETIC ENERGY Energy due to motion.

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LAMINAR FLOW Gas flow of sufficient velocity to allow the gas to flow smoothly over surface irregularities and obstructions.

LEAK A hole or permeable element through which leakage may occur under the action of a pressure difference.

LEAK DETECTOR A device for locating leaks and/or measuring the magnitude of the leakage.

LEED Low Energy Electron Diffraction

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MANOMETER An instrument for measuring the pressure of gases and vapors.

MASS SPECTROMETER An instrument which produces a beam of ions from a sample, separates the resulting mixture of ions according to their mass-to-charge ratios, and provides output signals which are measurements of the relative abundance of the ionic species present. A mass spectrometer usually consists of an ion source, a detector and a mass analyzer.

MEAN FREE PATH The average distance a gas molecule travels without colliding with another molecule or surface.

MECHANICAL PUMP A device with moving parts such as rotating vanes, a piston, or eccentric rotary members used for pumping gas or vapor.

MICRON A unit of pressure defined as 10-3 millimeters of mercury (E-3 torr).

MOLECULAR FLOW The movement of a gas through a channel under conditions such that the man free path is much greater than the dimension of a transverse section of the channel. The molecules collide mainly with the surfaces rather than with each other.

MONOLAYER A single layer of atoms (molecules) completely covering a surface.

MULTILAYER FILM A film which is a composite of two or more films which differ in some intrinsic property.

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NUDE GAUGE A vacuum gauge which does not have its own envelope; designed to be inserted into a vacuum system.

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OUTGASSING The evolution (setting-free, releasing) of gas from a liquid or solid under vacuum.

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PARTIAL PRESSURE The pressure of a designated component of a gaseous mixture. The sum of the partial pressures of all the component species in a mixture is equal to the total pressure.

PASCAL A basic unit of pressure equal to one newton per square meter or 7.5(E-3) torr.

PERMEATION The passage of gas through a solid. The process always involves diffusion through the solid and may involve surface phenomena such as sorption, dissociation, migration and desorption.

PHASE A state of matter; solid, liquid or gas.

PHYSICAL VAPOR A process whereby material is transferred in a DEPOSITION vaporized state from a source to a surface on which the material will condense.

PIRANI GAUGE A thermal conductivity gauge containing a heated filament having a large temperature coefficient of resistance. Because heat dissipation form the filament is a function of the gas pressure in a certain pressure range, filament resistance or power required to maintain o constant filament resistance can be correlated with gas pressure.

PLASMA An ionized gas containing approximately equal numbers of positive and negative charge carriers. A state of gaseous matter in which electrons, ions, atoms and molecules may coexist in an equilibrium distribution with overall, long-range electrical neutrality.

POLYCRYSTALLINE A film structure which consists of many crystallites.

PRESSURE The average normal force per unit area exerted by gas molecules impacting on a surface.

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RBS Rutherford Backscattering Spectrometry

REFRACTIVE INDEX Ration of the sine of the angle of incidence to the sine of the angle of refraction of light as it enters a body. It is also the ratio of the velocity of light in the body compared with the velocity of light in vacuum.

RESIDUAL GAS Gas remaining in the vacuum chamber after pump-down.

RESIDUAL GAS A device for measuring the amounts and species of ANALYZER various gases present in a vacuum chamber. Also referred to as a partial pressure analyzer or partial pressure gauge.

RESISTANCE HEATING Heating a material by passing an electric current through it.

RESISTIVITY Electrical property of a conductor that opposes the passage of a current and changes electric energy into heat. It is the reciprocal of conductivity.

RHEED Reflection High-Energy Electron Diffraction.

RIPPLE The alternating current component of the output of a direct current power supply.

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SECONDARY An electron produced by the bombardment of a material by a primary electron.

SIGHT PORTS Holes covered with the glass through which the inside of a vacuum system may be observed.

SIMS Secondary Ion Mass Spectrometry.

SINGLE CRYSTAL A film structure which is crystalline.

SOLENOID A valve in which the moveable members is actuated by an electromagnet.

SORPTION A generic term used to describe the uptake of a gas or vapor by a solid without distinction as to whether the process occurs by adsorption and/or absorption.

SPECTROPHOTOMETER A device which continually measure light intensity at specific frequencies over a broad band of frequencies.

SPUTTERING When an electrical discharge is passed between electrodes at a low gas pressure, the cathode electrode is slowly disintegrated under the bombardment of the ionized gas molecules. The disintegrated material leaves the electrode surface either as free atoms or in chemical combination with the residual gas molecules. Some of the liberated atoms are condensed on surfaces surrounding the cathode, the reminder are returned to the cathode by collision with gas molecules.

STOICHIOMETRY The part of chemistry dealing with the composition of substances in integral proportions.

SUBLIMATION The process of transition directly from the solid to vapor phase without passing through the intermediate liquid phase.

SUBSTRATE A support or carrier for a partial layer, layers, films or thin film component. Commonly a glass slide or polycrystalline alumina are used for thick film circuits and single crystals for single crystal film deposition.

SURFACE DAMAGE The physical changes of a surface structure to states of less regularity or symmetry, or the chemical changes in its composition.

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THERMISTOR GAUGE A form of Pirani gauge in which the temperature sensitive elements are made of a semiconducting material instead of metal.

THERMOCOUPLE GAUGE A thermal conductivity gauge which contains a heated filament and a bi-metallic thermocouple junction for the measurement of filament temperature a as function of gas pressure.

TORR A unit of pressure; 1/760th of a standard atmosphere.

TRACE ELEMENT An element which occurs as an impurity in small amounts; usually less than 1%

TRANSITION FLOW The flow of gas through a channel under conditions such that the mean free path is of the same order as the transverse dimensions of the channel. In this pressure range, the flow characteristics are determined by collision of the gas molecules with the surfaces as well as with other gas molecules.

TRAP A device used to capture and retain vapors and gasses on cold and/or adsorbent surfaces.

TURBOMOLECULAR PUMP An axial flow turbine for operation in the molecular flow range consisting of a series of alternate circular rotor and stator disks both of which have inclined blades designed to impart momentum change to gas molecules in a preferential direction from the pump inlet to the outlet.

TURBULENT FLOW Gas flow at high pressures and velocities, where the flow is not laminar.

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VACUUM The condition of gaseous environment in which the gas pressure is below atmospheric pressure. Generally classified in six pressure ranges: Low vacuum 25 to 760 torr Medium vacuum 10-3 to 25 torr High vacuum 10-6 to 10-3 torr Very high vacuum 10-9 to 10-6 torr Ultrahigh vacuum 10-12 to 10-9 torr Extreme ultrahigh vacuum below 10-12 torr

VACUUM CHAMBER The container or enclosure in a vacuum system that is evacuated and in which the process or experiment is performed.

VACUUM GAUGE An instrument for measuring gas pressure below atmospheric pressure.

VACUUM PUMP A device for reducing and maintaining the gas pressure in a vessel below atmospheric pressure, either by transferring the gas molecules out into the atmosphere or by capturing and holding them on surfaces within the pump.

VACUUM SYSTEM A complete assembly consisting of the vacuum chamber, pumps, lines, valves and monitoring instruments used to conduct a vacuum process or experiment.

VALVE A mechanical device by which the flow of gas of vapor may be started, stopped, or regulated by a moving part which opens or obstructs a passage.

VAPOR The gaseous phase of a substance that is normally a solid or a liquid at room temperature and atmospheric pressure.

VAPOR PRESSURE Usually means saturated vapor pressure; a fixed value at a particular temperature for all substances.

VISCOUS FLOW The flow of gas through a channel under conditions such that the mean free path is very small in comparison with the smallest dimension of a transverse section of the channel. At these pressures the flow characteristics are determined mainly by collisions between the gas molecules. The flow may be laminar or turbulent.

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