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NAK
Incorrect Reception handshake code. NOTE-NAK (derived from Not AcKnowledged) is one of the four standard handshake codes used in block transfer protocol. The code NAK (00010101) corresponds to the ASCII code that has the same pattern.
Nameplate gas
in mass flow devices, the gas, as labeled on the product, intended to be controlled or measured.
Nanogram (ng)
one billionth of a gram.
Nanometer (nm)
one billionth of a meter; used in the measurement of the wavelength of light.
Nanosecond (ns)
one billionth of a second.
National Electric Code (NEC) hazardous voltage
as defined by the NEC, voltage greater then 50 V. (Article 720)
National Electric Code (NEC) high voltage
as defined by the NEC, voltage greater than 600 V. (Article 710)
National Electric Code (NEC) low voltage
as defined by the NEC, voltage between 50 and 600 V.
National Electric Code (NEC) safe voltage
as defined by the NEC, voltage between 50 and 600 V.
National Fire Protection Association (NFPA)
a voluntary membership organization that promotes and improves fire protection and prevention and establishes safeguards against loss of life and property by fire.
National laboratories
a subset of federal laboratories concerned with research and innovation; the nine national laboratories are under the direction of the U.S. Department of Energy. Examples are Oak Ridge, Sandia, and Los Alamos. Contrast federal laboratories.
Nebula
see haze.
Nebulosity
see haze.
NEC
see National Electric Code.
Negative mask
see photomask, negative.
Neoplastic effects
production of tumors.
Netlist
An ASCII file containing a description of schematic design elements and their interconnections. Netlist transfer is the most common way of moving designs from one design system or tool to another.
Neutral beam
a stream of uncharged particles.
Nick
see chip.
Nitric acid (HNO3)
a strong, colorless or yellowish liquid oxidant that is highly corrosive and a potential fire hazard. This acid is prepared by the action of sulfuric acid on nitrates and by the oxidation of ammonia. Nitric acid is used to clean silicon wafers and etch metals.
Nitride etch
an etch process whereby unprotected portions of a silicon nitride layer are eroded to expose the initial oxide layer beneath the nitride.
Nitrogen (N2)
normally a diatomic gas, but also a cryogenic liquid (a liquid at low temperature). Its vapors are odorless, tasteless, and nonflammable. Nitrogen is used in purging, blanketing, pressurizing systems, and cooling systems. It also is used as a carrier gas in chemical vapor deposition and at ambient temperature for sintering and annealing.
Nitrogen trifluoride (NF3)
a toxic, odorless, and nonflammable gas that is a strong oxidizer and supports combustion. This gas is used as a source of fluoride ions in plasma processes.
Nitrous oxide (N2O)
an oxidizing, colorless, liquefied gas with a sweetish odor. It is toxic to humans when breathed. Nitrous oxide is used in the chemical vapor deposition of silicon dioxide and in plasma processes.
NMOS
Also called "N-Channel MOS" (metal oxide semiconductor). A type of MOSFET in which electrons are the dominant charge carrier in the semiconductor channel. The channel is N-type. NMOS devices run at least twice as fast as PMOS (P-Channel MOS) devices--the oldest type of MOS circuit-- because the mobility of electrons is higher than that of holes. Compare PMOS.
Nodules
in metal lid/preform assembly, lumps of plating extending above the surface of the lid.
Noise
Unwanted acoustic or electromagnetic disturbances, as opposed to desired signals. See signal.
Noise-limited height resolution
in surface characterization by noncontact optical profilometry, the root-mean-square height fluctuation around the mean of the measurement of the height for any given point on the surface.
Nominal feature dimension
the linear dimension of interest, such as the linewidth or contact hole width.
Noncritical seal area
on a semiconductor package that uses a lid or cover to effect the seal, the area of the sealing surface outside the critical sealing area. Contrast critical seal area.
Nonflammable
incapable of being easily ignited or of burning with extreme rapidity when lighted.
Nonisotropic
see anisotropic.
Nonliquefied compressed gas
a gas, other than a gas in solution, that under the charging pressure is entirely gaseous at a temperature of 21.1 degrees C (70 degrees F).
Non-Return to Zero (NRZ)
a digital waveform that undergoes only one transition per clock cycle.
Nonscheduled state
one of the six equipment states or conditions; a period of nonscheduled time during which equipment is not scheduled to be utilized in production. Such periods include offline training, unworked shifts, weekends, and holidays.
Nonscheduled time
any period that is not scheduled to be utilized, such as offline training, unworked shifts, weekends, and holidays. Also see nonscheduled state.
Nonsymmetrical valve
a valve not identical with respect to center line and not having similar flow and pressure characteristics in either direction.
Nonuniformity
of transmission lines and waveguides, the degree with which a characteristic quantity (for example, impedance) deviates from a constant value along a given path. (Copyright 1993 IEEE. All rights reserved.)
Non-volatile memory
Semiconductor memory which will not forget its data once the power is switched off. This is in contrast to volatile memory (e.g. DRAMs), which lose their information when there is no power supplied to the chip.
Normal astigmatism
in the measurement of photolithographic instruments, the difference in Z-axis position at each image site between the sagittal focal surface and the tangential focal surface. Astigmatism is a map of scalar values over the (X,Y) coordinates of the image field.
Normal operating differential pressure
in a mass flow controller, the range of differential pressure required by the device to meet its stated performance specifications.
Normal operating pressure, inlet and outlet
in a mass flow controller, the pressure range within which the device meets its stated performance specifications.
Normal operating temperature
in a mass flow controller, the temperature range within which the influence of ambient temperature on the performance is stated.
Normal surface
of a component test sample, an area of the sample that does not exhibit any visible defect when viewed under a scanning electron microscope, used to provide a baseline for comparison with any area exhibiting a defect.
Notch
1: an unexpected intrusion or reduction of linewidth in patterned geometries. May also be a V-shaped intrusion into the perimeter of a wafer. The intrusion is used to align the wafer during process. 2: on a semiconductor wafer, an intentionally fabricated indent of specified shape and dimensions oriented such that the diameter passing through the center of the notch is parallel with a specified low index crystal direction.
NPLY
Non Photo-Non Process Limited Yield.
NPN transistor
A two-junction transistor with an N-type collector and emitter and a P-type base. See bipolar transistor and complementary. Compare PNP transistor.
NRE
Non-Recurring Engineering. A one-time charge for photomask development, test and prototype tooling, and associated engineering costs.
NRZ
see non-return to zero.
Ns, nsec
Abbreviations for nanosecond (x10-9 second). One thousandth of a microsecond. Electronic signals travel approximately one foot per nsec.
N-type
1: describes a semiconductor material that has negatively charged conductivity (a surplus of electrons); material with free-carriers of electricity dominated by negatively charged ions. Also see conductivity type. 2: a variety of semiconductive material in which the majority current carriers are electrons, formed when donor impurities are incorporated into the crystal structure in small concentrations.
N-type silicon
Silicon which has been doped with phosphorus or arsenic. This makes the electrical carriers which make up the electric current negatively charged electrons.
Nucleation
the replating step in which a catalytic material, often a palladium or gold compound, is absorbed on a surface to act as sites for initial stages of deposition.
Number of anomalies
in microscopic analysis of metallic surface condition, the total number of defects per photomicrograph. Also called number of defects.
Number of defects
see number of anomalies.
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