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Vacuum
an absence of air or other gas.
Vacuum decay method
leakage detection determined by the loss of vacuum (increase in pressure), over a period of time within a vessel or piping system.
Vacuum source a vacuum generator or Venturi device designed to reduce pressure
within a piping manifold to a level below atmospheric pressure.
Vacuum valve
a shutoff valve that, when open, connects the system to a pressure less than atmospheric pressure.
Vacuum wand
a tool that uses suction on the back of an individual wafer to pick up the wafer.
Value-added operation
any operation required to meet the final performance criteria for the product, assuming every step is run optimally and without delays between operations.
Valve
1: a device that controls the flow or pressure of a gas. Valve functions can include shutoff, metering, backflow prevention, and pressure relief. [SEMI Chemicals/Gases, Vol. 1, 1990 (no longer in print)] 2: any component designed to provide positive shutoff of fluid media with the capability of being externally operated.
Valve seat
the internal sealing area of a valve, either seat or interference fit valve design.
Vapor
the gaseous form of substances that are normally in the solid or liquid state, and that can be changed to these states either by increasing the pressure or decreasing the temperature.
Vapor density
the weight of a vapor or gas compared to the weight of an equal volume of air.
Vapor phase reflow
a technique used for solder reflow that forms package interconnections.
Vapor pressure
the pressure exerted when a solid or liquid is in equilibrium with its own vapor. Vapor pressure is a function of the substance and of the temperature.
Vapor prime
surface preparation of wafers for the resist coat operation that occurs in an environment of hexamethyldisilazane (HMDS) vapor.
Variables
those characteristics of a part or process that can be measured. Examples are thickness in angstroms, step height in micrometers, and haze in parts per million. Variables are measured on a continuous scale.
Variation
the differences among individual outputs of a process. The sources of variation may be grouped into two major classes: common causes and special causes.
Varistor
From "variable-resistor". A non-linear, voltage-dependent device whose electrical behavior provides transient suppression performance. The device absorbs the potentially destructive energy of incoming transient pulses, thereby protecting vulnerable circuit components. Harris varistors are made from zinc oxide in the Dundalk, Ireland manufacturing facility. See MOV.
Vena contracta
in equipment exhaust systems, a point in a duct where the diameter of the air stream is smaller than the diameter of the duct.
Vent valve
a valve between the purge manifold piping system and a vent. [SEMI Chemicals/Gases, Vol. 1, 1990 (no longer in print)]
Venturi device
a flow device for generating a vacuum by means of air flow or purge-gas flow through a restricted orifice.
Verification
a process by which the correctness of a design result is confirmed through one or more of the following approaches: (1) formal or symbolic analysis of design, (2) simulation of the design in software form on a host computer, or (3) emulation of the design through implementation in a hardware or combined software/hardware form.
Verification run
any unit or units (product or nonproduct) processed by the equipment to establish that it is performing its intended function within specifications.
Verilog
A Cadence Design Systems logic simulator used in the FASTRACK design system. See FASTRACK.
Vertical orientation
see wafers, vertical.
Very Large Scale Integration (VLSI)
the placement of between 1,000 and 1,000,000 components on a die.
VHDL
VHSIC Hardware Description Language. Originally developed as a language for describing the design of an IC under the VHSIC (Very High Speed Integrated Circuit) program, this language, sponsored by the U.S. Department of Defense, is the military-mandated language for describing hardware functionality as well as a commercially viable standard for high-level descriptions of ICs. VHDL is important because it is required by military contracts, and because it is increasingly desired by commercial customers who use it to model systems composed of one or more parts from several vendors. VHDL will probably be the lasting standard among hardware description languages (HDLs). See VHSIC program.
VHF
Very High Frequency. (1) A high-performance, 20V linear bipolar process in production in Melbourne, Florida. It is dielectrically isolated and used for general analog applications. Several enhancements of this process are currently under development. (2) The portion of the radio spectrum between 30 and 300 megahertz (MHz). This includes television channels 2 through 13, the FM band, and other commercial communication bands.
VHSIC program
Very High Speed Integrated Circuit program. An initiative by the U.S. Department of Defense to extend integration levels and performance capabilities for military integrated circuits to meet or exceed those available in commercial ICs.
Via
an opening in the dielectric layer(s) through which a riser passes, or in which the walls are made conductive; an area that provides an electrical pathway from one metal layer to the metal layer above or below.
Vickers Hardness Number (VHN)
a measure based on a hardness test for metals in which a 136 degree diamond pyramid is pressed on the surface of the metal being tested by a load of 5 to 120 kg.
Virgin test wafer
see wafer, virgin test.
Virtual design
an approach to designing a product whereby the entire process is completed on a computer without the actual implementation in silicon. Design trade-off and implementation decisions, as well as verification exercises, occur entirely with the help of software tools. Only after all specifications are met and the designer is satisfied with the result does the actual implementation take place.
Virtual device
see virtual semiconductor device.
Virtual factory
a rapid prototyping software environment for factory design and manufacturing engineering based on computer simulations at various levels, such as process, device, circuit, equipment, and line.
Virtual integration
An industrial relationship between otherwise independent companies that allows them to emulate the business activities of vertically integrated firms and compete more effectively.
Virtual semiconductor device
a virtual control computer in a SECS message service/open systems interconnection network environment for the control of semiconductor equipment. Any number of virtual semiconductor devices may reside in a single physical computer system. Also called virtual device. Also see cluster controller.
Virtual tracking unit
an object or group of objects, such as a number of substrates or an individual die or mask group, that the factory floor control system treats as a single entity for purposes of tracking.
Viscosity
measurement of the flow properties of a material expressed as its resistance to flow.
Visual hazard alert
see sign.
Void
1: see dielectric void. 2: see glass void. 3: see metallization void.
Volatile memory
A memory device that does not retain stored information when power is interrupted. See non-volatile memory.
Voltage (V)
a measure of electrical potential. One volt causes one ampere of current to flow through one ohm of resistance.
Voltage regulator
A circuit (either an IC or a portion of an IC) whose purpose is to make the output voltage less variable than the input voltage. As an example, a voltage regulator might provide an output of 5 volts ±2% to a logic board from an input of 5 volts ±50%.
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