Ionization Glossary
Air Conductivity
The ability of air to conduct (pass) an electric current under the influence of an electric field. Back to top.
Air Ion
Air ions are molecules of one or more of the gases that make up air (nitrogen, oxygen, carbon dioxide, etc.) that have gained or lost electrons. If they lose electrons the molecules have a net positive charge, and are "positive ions". If they gain electrons, the molecules have a net negative charge, and are negative ions. Back to top.
Balance
The production of an equal ratio of positive and negative ions by ionizers. Back to top.
Charge
An excess or absence of electrons on the surface of an object. An excess of electrons causes the object to be negatively charged relative to ground. An absence of electrons causes an object to be positively charged. Back to top.
Conductor
A material that has low resistivity and conducts current easily. Materials that are conductors distribute charge over the entire conductive surface, even if charge is generated at a localized area. Back to top.
Discharge Time
The time required to reduce the static charge on a surface, also referred to as decay rate; the time in seconds necessary to reduce a 1000 volt charge to the CPM test plate to 100 volts was measured for each polarity at a representative 20% sample of the emitter locations. Back to top.
Electromagnetic Compatibility (EMC)
The electromagnetic radiation generated from a tool can propagate from place to place, possibly causing other tools in its vicinity to malfunction. The electromagnetic disturbance generated by any equipment must not exceed a level that allows radio, telecommunications, and other apparatus to operate as intended. Back to top.
Electrostatic Attraction (ESA)
The accelerated deposition of particles onto a surface due to the presence of electric field created by excess electrical charge on a surface. Once bonded to a charged surface, it is very difficult to remove the contamination. Back to top.
Electrostatic Compatibility (ESC)
Static charge generated in equipment is kept below a level at which it affects product or any part of the production process adversely. Inter-equipment transfer of products, reticles, and carriers should take place without affecting product or other nearby equipment. Back to top.
Electrostatic Discharge (ESD)
ESD is the uncontrolled transfer of static charge from one object to another. Back to top.
Electrostatic Field
An attractive or repulsive force in space that originates from the presence of electric charge. Back to top.
Electromagnetic Interference (EMI)
EMI is any energy that interferes with the normal operation of equipment. EMI can be radiated or conducted. Equipment lock-up is often misdiagnosed as a software or hardware problem, when ESD-induced EMI may be the true culprit. Back to top.
Electrostatics Management
The control of charge in manufacturing processes and cleanroom environments through grounding, static-dissipative materials, and ionization. Back to top.
Grounding
When charge can be conducted through a material, the solution to static charge problems is to provide a path for the charge to flow to ground. This solution works only on conductors and static-dissipative materials. While charge is mobile on a conductor or static-dissipative material, charge is not mobile on insulators. The only effective means of neutralizing static charge on insulators is through air ionization. Back to top.
Inductive Charging
This type of charging occurs when a charged object creates a stationary electrostatic field. The electrostatic field from the original object attracts opposite polarity charge to the surface of the new object placed within the field. If that object is grounded, then isolated from ground and removed from the field, it will hold an electrostatic charge. Back to top.
Insulators
Materials such as plastic, quartz, ceramics, glass and silicon that do not conduct current. Charge on an insulator will not distribute itself over the material's entire surface, but will stay fixed at the generating site. Back to top.
Ionization
Ions are molecules of the gases in air (nitrogen, oxygen, water vapor, and carbon dioxide) that have lost or gained electrons. Ionization systems work by increasing the conductivity of the air with the charged gas molecules. When ionized air comes in contact with a charged surface, the surface attracts ions of the opposite polarity. As a result, the static electricity is neutralized.Back to top.
Measurement Locations
The charge plate monitor (CPM) is tripod mounted directly beneath each emitter at the standard height. Where environmental factors prevent normal placement of the CPM, the exceptions are noted in the date comments. Back to top.
Service Recommendation
Quarterly emitter point cleaning and semiannual calibration is typical for most cleanroom applications. Environmental conditions should determine actual cleaning schedules. Emitter points should be replaced at two to three year intervals. Back to top.
Static Charge
Charge is a fundamental property of matter, dependent on the movement of electrons. When electrons flow through a conductor we can have an electric current. Charge can also be transferred between objects. Whenever two materials are brought into contact, and then separated, a charge exchange occurs between the two materials. One material gains electrons and becomes negatively charged, the other material loses electrons and becomes positively charged. This is known as triboelectric charging or friction charging. If one or both materials are isolated from ground or an insulator, the charge will remain on the material. This is what is known as static charge. Charge on a material may be transferred to ground or another object. This transfer is an electrostatic discharge. Back to top.
Timing and Voltage Swing
Each system controller and each emitter is adjusted to achieve industry standard swing peaks for rapid reduction of ambient static charges and for minimum net charge. Back to top.
Triboelectric Charging
Also known as friction charging, this event takes place whenever two surfaces in close contact are separated. One surface loses electrons and becomes positively charged while the other surface gains the same electrons and becomes negatively charged. After separation, each surface retains its positive or negative charge, unless the surface is conductive and a path to ground is provided. Back to top.
Voltage
The force applied between two points causing charged particles (and hence current) to flow. Back to top.
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