SEMATECH Dictionary of Semiconductor Terms

A-Am | An-Az | B | C-Ch | Ci-Com | Con-Cz | D-De | Df-Dz | E-En | Eo-Ez | F-Fl
Fm-Fz | G | H | I | J-K | L | M-Mes | Met-Mz | N | O | P-Ph | Pi-Pq | Pr-Pz | Q | R
S-Se | Sh-So | Sp-Sta | Ste-Sz | T-Th | Ti-Tz | U-V | W-Z

"U & V "

U-chart n		an attributes chart used to track the number of nonconformities with varying sample size, for example, to track the particle density per wafer. [SEMATECH]
ultrapure water (UPW) n		deionized and filtered water. [SEMATECH]
ultrashallow junction n		dopant junction in silicon in which the junction is less than 100 nm deep. [SEMATECH]
ultrasonic bonding n		a packaging process that involves high-frequency waves and pressure techniques to join two materials. [SEMATECH]
uncontrolled work area n		any area outside of a secondary containment system where people are likely to be present. [SEMI F6-92]
undercut n		in the leadframe of a dual inline semiconductor package produced by etching, a beveled edge caused by the etchant attacking the metal laterally as well as vertically. [SEMI G19-84] Also see etch factor.
undercutting n		the lateral etching into a substrate under a resistant coating, as at the edge of a resist image. [ASTM F127-84]
unencapsulated thermal test chip n		an unpackaged, specially designed silicon die with standard test junctions that, after mounting into a package, may be used to thermally characterize that package. This technique is useful in determining the difference between various vendors' packages and package designs. [SEMATECH]
unit n		any wafer, die, packaged device, or piece part thereof; includes product and nonproduct units. [SEMI E10-92]
unload v		to remove a cassette from the cassette stage of the equipment. [SEMI E23-91] Contrast load.
unscheduled downtime n		the total time during which equipment is not in a condition to perform its intended function because of unplanned downtime events. [SEMI E10-92] Also see unscheduled downtime state.
unscheduled downtime state n		one of the six equipment states or conditions; a period during which equipment is not in a condition to perform its intended function because of unplanned downtime events. [SEMI E10-92]
unstable		t 1 adj: ending toward decomposition or other unwanted chemical change during normal handling or storage. [SEMATECH] 2 n : a chemical that, in the pure state, or as produced or transported, will vigorously polymerize, decompose, condense, or will become self-reactive under conditions of shock, pressure, or temperature. [SEMI S4-92]
upper range input value n		in mass flow devices, the highest value of input at which the instrument is specified to operate. In mass flow controllers, this is full scale or the highest set point at which the instrument is specified. In mass flow meters, this is full scale or the highest actual flow value at which the instrument is specified. [SEMI E27-92]
uptime, equipment n		the amount of time during which the equipment is in a condition to perform its intended function; includes productive, standby, and engineering time; does not include any portion of nonscheduled time. [SEMI E10-92]
UPW		see ultrapure water.
usable resolution n		the smallest image that can be produced and subsequently processed in a given thickness of resist coating. [ASTM F127-84]
user n		in communications and control of semiconductor manufacturing equipment, a human or humans who represent the factory and enforce the factory operation model. A user is considered to be responsible for many setup and configuration activities that cause the equipment to best conform to factory operations practices. [SEMI E30-94]
vacuum n		an absence of air or other gas. [SEMATECH]
vacuum decay method n		leakage detection determined by the loss of vacuum (increase in pressure), over a period of time within a vessel or piping system. [SEMI F6-92]
vacuum source n		a vacuum generator or Venturi device designed to reduce pressure within a piping manifold to a level below atmospheric pressure. [SEMI Chemicals/Gases, Vol. 1, 1990 (no longer in print)]
vacuum valve n		a shutoff valve that, when open, connects the system to a pressure less than atmospheric pressure. [SEMI Chemicals/Gases, Vol. 1, 1990 (no longer in print)]
vacuum wand n		a tool that uses suction on the back of an individual wafer to pick up the wafer. [SEMATECH]
value-added operation n		any operation required to meet the final performance criteria for the product, assuming every step is run optimally and without delays between operations. [SEMATECH]
valve n		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. [SEMATECH]
valve seat n		the internal sealing area of a valve, either seat or interference fit valve design. [SEMATECH]
vapor n		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. [ASTM E41-86]
vapor density n		the weight of a vapor or gas compared to the weight of an equal volume of air. [SEMATECH]
vapor phase reflow n		a technique used for solder reflow that forms package interconnections. [SEMATECH]
vapor pressure n		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. [SEMI Chemicals/Gases, Vol. 1, 1990 (no longer in print)]
vapor prime n		surface preparation of wafers for the resist coat operation that occurs in an environment of hexamethyldisilazane (HMDS) vapor. [SEMATECH]
variables n		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. [SEMATECH]
variation n		the differences among individual outputs of a process. The sources of variation may be grouped into two major classes: common causes and special causes. [EIA 557]
vena contracta n		in equipment exhaust systems, a point in a duct where the diameter of the air stream is smaller than the diameter of the duct. [SEMI S6-93]
Venturi device n		a flow device for generating a vacuum by means of air flow or purge-gas flow through a restricted orifice. [SEMI Chemicals/Gases, Vol. 1, 1990 (no longer in print)]
vent valve n		a valve between the purge manifold piping system and a vent. [SEMI Chemicals/Gases, Vol. 1, 1990 (no longer in print)]
verification n		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. [1994 National Technology Roadmap for Semiconductors]
verification run n		any unit or units (product or nonproduct) processed by the equipment to establish that it is performing its intended function within specifications. [SEMI E10-92]
vertical orientation		see wafers, vertical.
very large scale integration (VLSI) n		the placement of between 1,000 and 1,000,000 components on a die. [SEMATECH]
via n		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. [SEMATECH]
Vickers hardness number (VHN) n		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. [SEMATECH]
virgin test wafer n		see wafer, virgin test.
virtual design n		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. [1994 National Technology Roadmap for Semiconductors]
virtual device		see virtual semiconductor device.
virtual factory n		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. [1994 National Technology Roadmap for Semiconductors]
virtual semiconductor device n		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. [SEMATECH] Also called virtual device. Also see cluster controller.
virtual tracking unit n		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. [SEMATECH]
viscosity n		measurement of the flow properties of a material expressed as its resistance to flow. [SEMATECH]
visual hazard alert		see sign.
void		1 : see dielectric void. 2 : see glass void. 3 : see metallization void.
voltage (V) n		a measure of electrical potential. One volt causes one ampere of current to flow through one ohm of resistance. [SEMATECH]

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