Acoustic Boundary Layer
The layer that shields a surface from being cleaned.  This layer thickness is a function of the frequency and the viscosity of the fluid.

Acoustic Pressure
The force applied through the cleaning solution from the transducer array.

Acoustic Streaming
The movement of molecules in a solution propelled by the acoustic pressure. Steady flow in the sound field.  Streaming enhances the transport of detached particles.  Acoustic streaming is a function of the frequency and the delivered intensity.

Adhesion
The molecular attraction exerted between the surfaces of unlike bodies in contact.

Adhesive
A substance capable of holding materials together by surface attachment.

Adsorption
Adsorption is a surface phenomenon that some products exhibit, whereby they form a physiochemical bond with substances. Not to be confused with absorption.

Al₂O₃ Particle
Particles of oxidized aluminum from common sources as ceramic or aluminum fixtures and tooling.

Alcohols
A series of hydrocarbon derivatives with at least one hydrogen atom replaced by an -OH group. The simplest alcohols (methanol, ethanol, n-propanol, and isopropanol) are good solvents for some organic soils, notably rosin, but are flammable and can form explosive mixtures with air. Their use requires caution and well-designed equipment.

Anion
A negatively charged ion.

APM
Commonly called SC-1 chemistry.  A mixture of DI Water, Hydrogen Peroxide, and Ammonium  Hydroxide in a 5:1:1 mixture.  Dilute APM has been proven to work for particle removal.  SC-1/APM is used for light organic removal.

Aqueous
Water-like, a liquid.

Aqueous cleaning
Cleaning parts with water to which may be added suitable detergents, saponifiers, or other additives.

Azeotrope
A mixture of chemicals is azeotropic if the vapor composition is identical to that of the liquid phase. This means that the distillate of an azeotrope is theoretically identical to the solvents from which it is  distilled. In practice, the presence of contaminants in the solvent slightly upsets the azeotropy.

Bond
To attach by means of adhesive.

Buffer
A solution that minimizes changes in hydrogen ion concentration that would otherwise occur as a result of a chemical reaction.

Buffering agent
Drives an acidic or alkaline solution to neutral.

Cation
A positively charged ion.

Cavitation
The low pressure portion of a low frequency wave creates a small bubble or cavity in the solution.  These bubbles are filled with vapor and are oscillated by the sonic energy.  These bubbles collapse resulting in cavitation.  Cavitation has sufficient power to overcome the particle to substrate adhesion forces.  The threshold pressure required to initiate cavitation is a strong function of the pulse width and the power input.

CFC
Chlorofluorocarbon.

Chlorofluorocarbon
An organic chemical composed of chlorine, fluorine, and carbon atoms, usually characterized by high stability.

Cleaning
The removal of soil or unwanted matter from a surface to which it clings.

Cleaning Efficiency
The ratio of particles on a material before the cleaning process to the particles remaining after cleaning.

CMP - Chemical Mechanical Polish
A term describing the process for a type of planarization allowing multiple levels of metallization to provide denser circuitry on a silicon chip.

Collapse
To shrink together suddenly.

Colloid
A substance that remains suspended in a solution or fails to settle out of solution.

Continuous Wave
Sometimes abbreviated as "CW" typically describes an acoustic wave that remains on for the full process cycle time.

Copolymer
The product of simultaneous polymerization of two or more polymerizeable chemicals known as monomers.

Contamination Free Manufacturing
The search to produce higher yields on wafers has brought this concept to the forefront of semiconductor manufacturing.  Throughout the manufacturing process all tooling has a goal of adding zero foreign material to the silicon being produced.

Crystal
The type of manmade piezoelectric material used as the energy transducer in megasonic cleaners.

DI Water
"Dee - Eye Water".  Deionized Water of ultra-high purity and high electrical resistance used for cleaning various semiconductor substrates.

Diffusion
The migration or wandering of the particles or molecules of a body of fluid matter away from the main body through a medium or into another medium.

Dilute
To make weaker by adding water or some other liquid.

Dispersion
To distribute throughout.

Drag
The cleaning process frequently uses successive tanks for liquid based cleaning.  The liquid that is carried from the first tank to the second along with the substrates being cleaned.

Dump Rinse
A method of rinsing semiconductor substrates following a cleaning bath.  DI water is sprayed over wafers in a rinse tank until the water covers them and the water is then rapidly drained from the tank.  This cycle is repeated several times.

Effective Power
The measure of the forward minus reflected watts of RF power.

Electrostatic
An electrical characteristic typically used here with reference to attractive forces or electrical discharge through a spark.

Forming
A process in which the shape of plastic pieces such as sheets, rods, or tubes are changed to a desired configuration.

FPMS
Is the cleaning solution consisting of DI Water, Hydrofluoric Acid, Hydrogen Peroxide, and a surfactant in the ratio of 0.5% HF and 10% H202 in DI Water with a non-ionic surfactant. Proponents of FPMS believe that FPMS in a megasonic cleaner will provide better particle removal than SC-1.

Frequency
The rate of occurrence.

Frequency Matching
Matching the driving frequency of the generator to the natural frequency of the crystal used as a transducer.

Glass
A hard substance that can be seen through and breaks easily.

H₂0₂
Hydrogen peroxide.  A strong oxidizing chemical used in particle removal chemistries.

H₂S0₄
Sulfuric Acid is a corrosive acid used in cleaning; commonly used in SPM for heavy organic removal.

Halar
Trade name for ECTFE, the best chemically resistant material available and it continuously handles high temperatures.

HCL
Hydrochloric Acid is a corrosive acid used in particle removal chemistries. Commonly found in SC-2 or HPM solutions used for metallic removal.

HF
Hydrofluoric Acid.  A corrosive acid used in etching and cleaning.  Commonly used for the removal of metals or thin oxides of glass.

HPM
Commonly called "SC-2 chemistry".  It is a mixture of DI Water, Hydrogen Peroxide, and HCL at a 5:1:1 ratio.  Used for metallic removal.

Hydrocarbon
An organic chemical composed only of hydrogen and carbon. Gaseous or volatile hydrocarbons are flammable.

Hydrophone
An instrument used to sense the sound pressure in a liquid.

Hydrophylic
The surface of the material may be wetted  by the solution in a sheeting action.

Hydrophobic
Water hating or having a strong aversion to water. The surface of the material may not become wetted by the solution.

Ion
An atom or group of atoms that is not electrically neutral but instead carries a positive or negative electric charge.

Isopropanol
Also known as isopropyl alcohol.

KOH
Potassium Hydroxide.  A corrosive base chemical, commonly called Lye, used for etching and cleaning in the semiconductor and cleaning processes.

Leaded surface mount
A surface mount component (SMC) whose external component connection consists of formed leads.

Megasonic Cleaner
An acoustic bath agitated by frequencies typically between 700 KHz and 1.2 MHz.

Micro Streaming
The streaming near bubbles in the sound field caused by the vibration of the bubble in the fluid due to pressure changes.  This vibration due to pressure changes causes currents and contributes to particle cleaning.

Micro Roughening
A roughening or pitting of the substrate surface from cleaning.

Miscible
Capable of being mixed in any ratio without separation of two phases.

Modular
A unit type of construction allowing easily replaced subassemblies during maintenance.

Monomer
The simplest repeating structural unit of a polymer.  For additional polymers this represents the original unpolymerized compound.

Natural Frequency
The frequency at which a crystal will oscillate at its natural resonance.

NH₄OH
Ammonium Hydroxide.  A corrosive base chemical used in particle removal chemistries.  Commonly found in SC-1 and APM solutions used for light organic removal.

Nitride
Silicon Nitride SiN₃

Oxide
Silicon dioxide SiO₂

Ozone
A gas formed when oxygen is ionized by, for example, the action of ultraviolet light or a strong electric field. It has the property of blocking the passage of dangerous wavelengths of ultraviolet light. Although it is a desirable gas in the stratosphere, it is toxic to living organisms at ground level (see volatile organic compound).

Particles
Any solid pieces of foreign material on the surface of the substrate or in equipment environments.

Photochemical reaction
A chemical reaction caused by light or ultraviolet radiation.

Photoresist
A photomechanical product, in the form of a liquid or a laminated dry film, used in the manufacture of printed circuits. Certain types require the use of large quantities of ozone-depleting hydrochlorocarbon solvents, mostly 1,1,1-trichloroethane and methylene chloride, for their processing.

Piezoelectric Crystal
Typically a manmade crystal with the correct properties to produce vibrations when excited by an electrical current.

PMT - Photo Multiplier Tube
Used as an amplifier for investigating sources of light.

Polyethylene
Commonly called HD or PE.  A plastic that is resistant to water solutions of acids, alkalis and salts as well as large numbers of organic solvents. Unsuitable for concentrated oxidizing acids.

Polymers
Compounds of very high molecular weights that are made up of a large number of simple molecules which have reacted with one another.

Polypropylene
Commonly called PP.  Chemical resistance similar to that of PE but suitable for higher temperatures.

Polyvinylidene Fluoride
Commonly called PVDF, trade named "KYNAR" and SYGEF.  A highly dense high strength chemically inert thermoplastic.  Resistant to acids, solutions of salts, aliphatic, aromatic, and chlorinated hydrocarbons, alcohols and halogens.  PVDF, KYNAR, and SYGEF may have different compatibility specifications depending on the supplier and compound used.

Polytetrafluoroethylene
Commonly called TFE, PTFE, ECTFE.  Trade named "TEFLON" and "Halar", is a highly corrosion resistant fluoropolymer with temperature resilience to 300 degrees ECTFE can also be thermo-formed.

Precision cleaning
Cleaning of high-precision mechanical parts and electronic sensory devices, as opposed to general metal cleaning. This is usually done under controlled atmospheres, notably in clean-rooms with low particle contamination.

PSL - Poly Styrene Latex
Material used to manufacture submicron spheres used in the study of particulate contamination removal and measuring equipment

Pulsed
To be switched on and off at variable rates or frequencies.

Pulsed Wave
Sometimes abbreviated as "PW" typically defines a wave that is turned on and off at some given frequency.

Quartz
A clear vitreous solid, or glass, produced by diffusion of a very pure form of quartz or rock crystal, fused quartz or silica glass.  Quartz glass is able to withstand large and rapid temperature changes.

RF Power
Radio Frequency AC voltage used to drive the PZT megasonic transducer crystal.

Scrubbed Exhaust
Vented exhaust that is treated typically by a water wash before it is discharged to atmosphere.

SC1
A cleaning solution developed by RCA Corp. made up of H₂0:H₂0₂:NH₄0H in a typical ratio of 5:1:1.

SC2
A cleaning solution developed by RCA Corp., comprised of DI Water, Hydrogen Peroxide, and Hydrochloric Acid in a ratio of 5:1:1.  Commonly used as a chemistry for removal of metallic, also called HPM.

Shear
The action of sliding one fixed object from another.

Slurry
A semi-fluid substance, usually a mixture of abrasive compounds in an aqueous solution.

Solvent
Although not a strictly correct definition, in this context a product (aqueous or organic) designed to clean a component or assembly by dissolving the contaminants present on its surface.

Sonoluminescence
Megasonic energies form tiny bubbles in the cleaning solutions that give off a minute amount of light when they collapse.
The weak emission of light which can occur when a liquid is exposed to sonic energies.  Thought to be caused by the collapsing localized cavity in the liquid causing chemical reactions which emit photons.

Sound Intensity
The measure of the power level of the acoustic energy.

SPM
Chemistry used for heavy organic removal consisting of DI Water, Hydrogen peroxide, and Sulfuric Acid.

Streaming Velocity
The velocity of the cleaning wave in the fluid, a function of energy, geometry, fluid density, fluid viscosity, and speed of sound in the fluid.

Surfactant
A surface active solution, usually reduces the ability for particles to adhere. A material that is used to lower the surface tension of a liquid. A product designed to reduce the surface tension of water. Also referred to as tension-active agents/tensides. Detergents are made up principally from surfactants.

Switched
The transfer of RF power between multiple crystals in an array.

Thermoplastic
A plastic capable of being repeatedly softened by increases in temperature and hardened by decreases in temperature.

Transducer
The device that is used to transfer energy into the cleaning solution bath.

Tungsten
A metal element with the symbol W (Wolfram)

Ultra Pure Water
A very high grade of DI water.

Vapor phase cleaning
A cleaning process, usually with CFC-113 solvent or hydrochlorocarbon solvents, in which the final rinse of the parts being cleaned is achieved by condensing solvent vapors on the parts.

Velocity
The rate of motion in a certain direction.

VLSI
Very Large Scale Integration, is a description of a type of semiconductor processing method.

Volatile organic compound (VOC)
The environmental or legislated definition: Constituents that will evaporate at their temperature of use and which, by a photochemical reaction, will cause atmospheric oxygen to be converted into potential smog-promoting tropospheric ozone under favorable climatic conditions. Some areas classify a substance to be a VOC based on its vapor pressure. Scientific definition: Any hydrocarbon, except methane and ethane, with a vapor pressure equal to or greater than 0.1 mm Hg.

Weir Overflow
The method of rinsing substrates in a tank by which the solution is made to flow over a weir or dam carrying away the foreign material.

Wetting agents
Another name for surfactants.

Wetting
The action by which a cleaner penetrates and loosens the substrate-soil bond by lowering surface and interfacial tension.

Zeta Potential
The ionic forces between a particle and another material.  These forces are measured in mV and may be positive or negative.  The Zeta potential decreases in higher pH solutions.