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Terms used in the Fabrication of Wafers

 

Back End

    Referencing semiconductor manufacturing, the package assembly and    

    test stages of production, includes burn-in and environmental test

    functions.

 

Bonded Wafer

    Composite dielectrically isolated substrate formed by fusing together (at

    high temperature) the oxidized surfaces of two individual silicon

    substrates.

 

Bonding

    The process of connecting wires from the package leads to the chip (or die)

    bonding pads. Part of the assembly process. A small-diameter gold or

    aluminum wire is bonded to the pad area by a combination of heat and

    ultrasonic energy.

 

Bipolar

    A class of semiconductor device in which both holes and electrons act as

    charge carriers. Any device that carries current across a pn-junction is a

    bipolar device.

 

Bipolar Transistor

    An active semiconductor device formed by two p-n junctions whose function

    is amplification or switching of an electric current. Bipolar transistors have

    three sections: emitter, base, and collector.

 

Chemical Etching

    An acid bath to remove surface damage and to make the silicon crystal

    slices thinner.

 

Chemical Mechanical Polishing (CMP)

    A process of flattening and polishing a wafer by combining chemical    

    removal with mechanical buffing.

 

Chemical Vapor Deposition (CVD)

    A gaseous process that deposits insulating films or metal onto a wafer at

    an elevated temperature.

 

Chip

    A semiconductor material, single crystalline in nature, which one or

    multiple active or passive solid-state devices are formed.

 

Circuit

    Combination of electrical or electronic components, interconnected to

    perform one or more specific functions.

 

CMOS (Complementary Metal-Oxide Semiconductor)

    A MOS technology in which both p-channel and n-channel components are

    fabricated on the same die to provide integrated circuits that use less

    power than those made with other MOS or bipolar processes.

 

CMP (Chemical-Mechanical Polish)

    Or Planarization; the process of improving the semiconductor's surface.

 

Coating

    The process of applying photoresist to a wafer, generally by dispensing a

    small amount of photoresist in the center of a wafer and then spinning the

    wafer at a high rate to spread and dry the photoresist (aka spin coating).

 

Complementary

    A term describing ICs that employ components of both polarity types

    connected in such a way that operation of either is complemented. A

    complementary bipolar circuit employs both NPN and PNP transistors. A

    complementary CMOS circuit (CMOS) employs both n-channel and p-channel

    devices.

 

Deposition

    The process in which materials are deposited onto a substrate. Usually

    refers to thin conducting or insulating films used to form MOS gates,

    capacitors, thin-films resistors, and the interconnect system for an IC.

 

Die

    A single square or rectangular piece of semiconductor material into which a

    specific electrical circuit has been fabricated.

 

Die Area

    The length of a die multiplied by the width of the die.

 

Die Bonding

    The method of securing the die to a package with conductive adhesives or

    metal alloys.

 

Die Cost

    The cost to produce a good die through the wafer fabrication and wafer

    test steps.

 

Die Size

    The size of a die. May be expressed as the length time the width or in

    area.

 

Die Sort

    The process of sorting out good and bad die on a wafer .

 

Die Yield

    The number of good die divided by the number of die tested .

 

Diode

    A two electrode semiconductor device that utilizes the rectifying properties

    of a p-n junction or a point contact .

 

DIP (Dual In-line Package)

    The most common IC package, which can be either plastic or ceramic.

    Circuit leads or pins extend symmetrically outward and downward from

    opposite sides of the rectangular package body.

 

Discrete Device

    A class of electronic components that includes power transistors and    

    rectifiers, each of which contain one active element. In contrast, ICs

    typically contain hundreds, thousands, or millions of active elements in a

    single die.

 

Dopant

    An impurity element that is deliberately added to a semiconductor.

 

Electrical Conductivity

    The ability of a material to carry an electric current; it is the reciprocal of

    resistivity with units of ohm [-1] cm [-1]

 

Electrical Resistance

    The measure of the difficulty of electric current to pass through a given

    material; its unit is the ohm.

 

Elementary Semiconductor

    A semiconductor made of a single element, Silicon is the primary example,

    though both Carbon (Diamond) and Germanium are also elementary

    semiconductors. This type of semiconductor usually exhibits a diamond

    crystal lattice.

 

Encapsulation

    Term used to describe the packaging of the chip.

 

Epitaxy

    The controlled growth of one material on another. In IC manufacturing, this

    often means that an n-type epitaxial layer is grown by deposition on a p-

    type substrate.

 

Extrinsic semiconductor

    A semiconductor material that has been doped with an n-type or p-type

    element .

 

Fab (Fabrication)

    Referencing semiconductor manufacturing, fabrication usually refers to the

    front-end process of making devices and integrated circuits in

    semiconductor wafers, but does not include the package assembly (back-

    end) stages.

 

FEOL (Front End Of Line)

    The first steps of the IC fabrication process where the individual active

    devices (transistors, resistors, etc.) are patterned in the semiconductor.

 

Forward Bias

    Bias applied to a p-n junction in the conducting direction, majority carrier

    electrons and holes flow toward the junction so that a large current flows.

 

Front End

    The fabrication process in which the integrated circuit is formed in and on  

    the wafer.

 

Gate

    The control electrode or control region that exerts an effect on a

    semiconductive region that it is directly associated with, so that the

    conductivity characteristics of the semiconductive region are altered in a

    temporary manner - often resulting in an on-off type switching action.

 

Ground Loop Noise

    An undesirable voltage generated in the common reference of a relatively

    low-level signal circuit by magnetic fields or by the return or reference

    currents produced by relatively high-power circuits connected to the same

    circuit reference (ground). This is a potentially detrimental condition,    

    generally caused by poor circuit layout of a PC board.

 

Gullwing

    A common lead form used to connect surface mounted packages to the

    printed-circuit board. Package sits on top of the PCB.

 

Integrated Circuit (IC)

    A single semiconductor chip or wafer which now contains thousands or

    millions of circuit elements per square centimeter.

 

Isolation

    An electrical separation between areas of an integrated circuit.

 

Isotropic

    A material with properties that are the same in all directions.

 

Junction

    The line or plane where the level of P Doping and N doping are equal.

 

Laser

    Acronym for Light Amplification by Stimulated Emission of Radiation, a

    light amplification process or device that is used to produce monochromatic

    coherent radiation in the infrared, visible, and ultraviolet regions of the

    electromagnetic spectrum.

 

Light Emitting Diode (LED)

    A semiconductor p-n junction device that is optimized to release light of

    approximately the band gap energy when electrons fall from the conduction

    band to the valence band. A diode that emits monochromatic (single color)

    light when forward biased. The emitted light can be red, yellow, orange,

    green, blue, or non-visible infrared.

 

Liquid Crystal Display (LCD)

    A display having conductive segments or dots deposited on the inside

    surfaces of two transparent glass plates separated by a crystal in liquid

    form. When energized with AC voltage in the presence of light, the

    selected segments will provide a black-tone or gray readout.

 

Monolithic IC Technology

    A technique of circuit fabrication where all of the devices in a circuit are

    placed on the same chip.

 

MOSFET

    Metal Oxide Semiconductor Field Effect Transistor.

 

N-Type

    Silicon doped with phosphorous becomes a substance with loosely held

    electrons. This is called n-type silicon.

 

NPN Transistor

    Bipolar transistor with n-type emitter and collector regions separated by a

    p-type base

 

Optoelectronic Device

    Device that is responsive to or that emits or modifies light waves.

    Examples: LEDs, optical couplers, laser diodes, and photo detectors opto-

    electronic are materials that can either produce an electric current from

    light or produce light from a current.

 

Outdiffusion

    Solid-state diffusion of impurities from the substrate underneath into the

    grown layer during its deposition.

 

P-Type

    Silicon doped with acceptor impurity (III) such as boron (p-type silicon).

 

P-Type Semiconductor

    The density of electrons in the conduction band is exceeded by the density

    of holes in the valence band. P-type behavior is induced by the addition of

    acceptor impurities, such as boron, to the crystal structure of silicon.

 

Package

    The sealed, protective container that houses an electronic component or

    die. External terminals provide electrical access to the components inside.

    Packages provide for power and signal distribution, power dissipation, and

    protection of the circuits.

 

PCB

    A thin board which electronic components are fixed by solder. Component

    leads and integrated circuit pins may pass through holes ("vias") in the

    board or they may be surface mounted, in which case no holes are    

    required.

 

Phosphorus (P)

    N-type dopant commonly used for the emitter diffusions in standard bipolar

    IC technology.

 

Photodetector

    A device capable of sensing light and converting it to electricity.

 

PN-Junction

    The interface and / or region of transition between p-type and n-type

    semiconductors.

 

PN-Junction Diode

    A (switching) device having two terminals connected to opposite type

    semiconductors with a junction, and exhibiting a non-linear current-voltage

    characteristic

 

PNP Transistor

    A semiconductor junction transistor with a p-type collector and emitter,

    and an n-type base. Current amplification arises from the injection of holes

    from the emitter into the base, and their subsequent collection in the

    collector.

 

QFP (Quad Flat Pack)

    A common package for ICs with higher pin counts.

 

Rectifier

    A circuit component, usually a diode that allows current to flow in one

    direction unimpeded but allows no current flow in the other direction.

 

Resistor

    A device used in electric circuits to limit the current flow or to provide a

    voltage drop.

 

Reverse bias

    Bias applied to a p-n junction in a direction for which the flow of current is

    inhibited; majority carrier electrons and holes flow away from the junction.

 

Reverse Gullwing

    Acommon lead form used to connect surface mounted packages to the

    printed-circuit board. Package sits under of the PCB.

 

RTO (Rapid Thermal Oxidation)

    An oxidation process performed in a rapid thermal processing (RTP) tool.

 

RTP (Rapid Thermal Processing)

    A single-wafer processing tool that uses high intensity lights or other

    sources to heat and cool the wafer in milliseconds.

 

Semiconductor

    A material whose electrical conductivity is midway between that of an good

    conductor and a good insulator; a type of material having a lower energy

    Valence band that is nearly completely filled with electrons and a higher

    energy Conduction band that is nearly completely empty of electrons, with

    a modest energy gap between the two bands; pure materials usually

    exhibit electrical conductivity that increases with temperature because of

    an increase in the number of charge carriers being promoted to the

    Conduction band.

 

Semiconductor Device

    An electronic device whose essential characteristics are governed by the

    flow of charge carriers within a Semiconductor.

 

Semicustom IC

    An integrated circuit in which a portion of the circuit function is predefined

    and unalterable, while other portions can be configured to meet the

    designer's specific needs. Semicustom ICs can be analog, digital, or mixed-

    signal.

 

SIT (Static Induction Transistor)

    A short-channel field effect transistor, usually used in High Power RF

    systems.

 

SOP (Small Outline Package)

    Similar to a miniature plastic flat pack, but with gullwing leadforms

    primarily or wholly constructed for surface mounting. Also called an SO

    package.

 

 SOS (Silicon-On-Sapphire)

    A type of SOI technology in which a layer of silicon is epitaxially grown on

    a sapphire wafer, with specific regions subsequently etched away between

    individual transistors. Each device is thus totally isolated from other

    devices.

 

Substrate

    The underlying material on which a microelectronic device is built. Such

    material may be electrically active, such as silicon, or passive, such as

    aluminum ceramic

 

Surface States

    These are states (within the bandgap, similar to dopants) at the edge of

    the semiconductor crystal that arise from incomplete covalent bonds, very

    thin oxides or other impurities, and other effects from crystal termination.

 

Test Wafers

    Wafers that are processed through part or all of a fabrication sequence and

    then used to measure the results of the processing.

 

TFT (Thin Film Transistor)

    Transistors formed in polycrystalline or amorphous silicon layers. used in

    AM display for pixel driving control. Active matrix displays provide sharper

    images than passive matrix displays.

 

Thermistor

    A resistive circuit component having a high negative temperature

    coefficient of resistance so that its resistance decreases as temperature

    increases.

 

Thyristor

    A family of semiconductor devices that exhibit bi-stable current-voltage

    characteristics and can be switched between a high-impedance, low-current

    "off" state and a low-impedance, high-current "on" state. Primarily used for

    power switching applications.

 

Vapor Deposition

    A processing step in the manufacture of optical glass fiber to reduce the

    inherent metallic impurities in the material, thereby minimizing light

    distortion.

 

VCSEL

    Abbreviation for Vertical Cavity Surface Emitting Laser. VCSEL is a laser

    diode that emits light in a cylindrical beam vertically from the surface of a

    wafer, in contrast to edge emitting lasers. VCSELs have applications in

    fiber optic communications devices, bar code scanning operations, optical

    storage, laser printing, and encoders.

 

Wafer

    A round thin slice disc (10-30 mils thick) of a semiconductor material

    (silicon), typically four to eight inches in diameter that is used as the

    substrate for active solid-state devices in discrete or monolithic integrated

    circuit form.

 

Wafer Fabrication

    The series of steps used to build an IC or device in and on a wafer.

 

Wafer Fabrication Facility (Wafer Fab or Fab)

    A facility where the wafer fabrication process is performed. Fabs include a

    high quality cleanroom as well as support systems such as ultrapure water,

    gas and chemical generation and delivery systems, waste water treatment,

    extension HVAC equipment, as well as other support functions.

 

Wafer Probe

    The test step where each individual die on a wafer surface is tested and

    bad die are marked as bad. Also called wafer test or wafer sort.

 

Wafer Size

    The diameter of a wafer ranging from 4, 5, 6, 8 or 12 inch wafers (4-inch

    wafer is 100 millimeters , 3.937 inches).

 

Wafer Yield

    The number of wafers completed through the wafer fabrication process,

    divided by the numbers of wafers started into the wafer fabrication

    process, multiplied by 100.

 

Yield

    The number of good units after testing.

 

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Last modified: 05/06/09