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Semicyclopedia is an encyclopedia of semiconductor terminology. It is a collection of definitions and explanations of the technical terms and alphabet soup abbreviations commonly accepted in the industry and academia.

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Atomic Force Microscope: AFM is a non-destructive surface topography analysis technique that provides surface topographic image with a resolution in order of angstroms. A very sharp silicon tip with a radius in the order of ~10A is scanned close to the sample surface to get surface topology. AFM is a powerful tool to investigate surface roughness of silicon wafer under the gate dielectric.


Atomic Layer Deposition: Closely related to conventional CVD, ALD is a thin film deposition technique that deposits very thin films with an excellent film uniformity and conformality. Single crystal semiconductor films such as Si, Ge and GaAS, metallic films such as tungsten and copper, and dielectric films such as oxides and nitrides can be deposited with ALD. Also known as ALCVD.


Atmospheric-pressure Chemical Vapor Deposition (see also CVD).


A mixture of Ammonia hydroxide, hydrogen Peroxide and water used for cleaning wafer surface primarily to remove organic particles.


 Anti-reflective Coating: a thin layer of dielectric film, such as SiN, coated over the wafer surface to improve lithography resolution by reducing light scatter from the wafer surface


 ArF is a source of an excimer laser that produces high power laser at a wavelength of 193nm.


Application Specific Integrated Circuits: As opposed to general purpose IC's, ASIC is designed and produced for a certain specific application. Also known as custom IC's. 
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Back End of the Line: BEOL typically refers to processing steps that involve ILD deposition, contacts and metal interconnects. See FEOL.


BiCMOS refers to circuits and process technology that offer both bipolar junction transistors (BJT) and CMOS transistors on the same chip. BiCMOS combines high current driving capability of BJT and low power consumption of CMOS. BJT is typically used to drive a large capacitive load while CMOS transistors are used to perform logic functions. BiCMOS technology is more complex and more expensive than CMOS technology, and typically serves niche markets.

Bird's Beak

During LOCOS (local oxidation of silicon) oxidation, two-dimensional oxidation occurs at the edge of field oxide. As a result, oxidation extends into the active area at the surface underneath the silicon nitride, forming a bird's beak. Because of bird's beak, the effective area of the active region is reduced. In the bird's beak region of gate oxide, oxide thinning can occur due to Kooi effect (also known as “white ribbon” effect). See Kooi effect.


Bipolar Junction Transistor: BJT has three parts; collector, base and emitter. In a vertical BJT, the emitter is the most heavily doped region and the collector the least heavily doped. “Bipolar” refers to the fact that two types of charge carriers (electron and hole) contribute to the current flow, one being the majority carrier and the other the minority carrier. In an NPN BJT, electron is the majority carrier. In a PNP BJT, hole is the majority carrier. In contrast, MOSFET is a “unipolar” device in the sense that only one type of charge carrier is responsible for the current flow (See MOSFET). BJT is characterized by high current gain and high switching speed. However, its large transistor size and high power consumption limit its use in very large scale integration. BJT transistor effect was first discovered by three Bell Labs researchers in 1947. This discovery led them to winning the Nobel Prize in physics in 1956. To learn more about the history of transistors, visit the following site. http://www.nobel.se/physics/educational/transistor/history/index.html


Barrier Metal Deposition: Barrier metal is a thin metallic film deposited in cotacts, via and under the metal interconnects. The purpose of barrier metal is to prevent tungsten from reacting with material underneath during contact fill process or to serve as a diffusion barrier to Cu interconnects. TiN, TiW and TaN are the typical barrier material.


Buffered Oxide Etch: Silicon dioxide etching solution made of a mixture of NH4F, HF and H2O.


Borophosphosilicate Glass: BPSG oxide is typically used in the back end of the flow in the semiconductor process to passivate the surface and to provide smooth topology. The oxide is doped with boron and phosphorus, which gives BPSG a gettering capability of sodium or metallic mobile ions, and allows it to flow at a lower temperature.


Borophosphosilicate tetraethylorthosilicate: BPTEOS is a BPSG film produced using TEOS instead of silane (SiH4) that is used in a more conventional BPSG film. BPTEOS produces void-free dense film (see also TEOS).


Berkeley Short-channel IGFET Model: BSIM is a MOSFET model developed by researchers at EE department of University of California, Berkeley for MOSFET circuit simulation. BSIM is one of the most widely used device models for circuit simulation today.


Barium Strontium Titanate (BaSr)TiO3: a high k dielectric material with dielectric constant in the range of 160-600 used in DRAM storage capacitors.


Biased Thermal Stress: BTS is one of the important techniques to evaluate the reliability of dielectric film. In a BTS test, an oxide capacitor is put under an accelerated voltage stress at a high temperature and electrical parameters, such as flat band voltage, are measured as stress progresses.   
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Charge Coupled Device: CCD uses a packet of charge (electrons or holes) that is transferred along the surface of semiconductor underneath the electrodes under control of clock signals. Signal processing is performed during charge transfer or at the output. Imaging is one of the most important applications of CCD, such as image sensor in the video cameras.


Critical Dimension: CD is the feature size defined by lithography or etch process. Usually, it refers to the minimum feature size for a particular layer in semiconductor processing. Feature size defined by litho process is commonly called DICD, and the final feature size after etch is commonly called FICD.


Complementary MOS: CMOS refers to circuits and process technology that provide both P-ch and N-ch MOSFET on the same chip. In CMOS circuits, P-ch MOSFET acts as an active load and N-ch MOSFET acts as a pull-down driver. In a steady state, CMOS circuits consume extremely low DC power because there is no DC current path from the power supply (Vcc) to the ground (Vss), making CMOS an ideal candidate for a large scale integration. In CMOS technology, P-ch MOSFETs are formed in N-well and N-ch MOSFETs in P-well. This is called “twin-well” CMOS technology. CMOS technology has become the mainstream technology in today's IC industry for most of logic and memory products (see Technology section of this Web site).


Chemical Mechanical Polishing (or Planarization): CMP is a semiconductor fabrication process to planarize wafer surface. Wafer surface is grinded by a rotating disc with chemical slurries aiding polishing process. Metals such as tungsten, aluminum, copper, and dieletrics such as oxide, and poly-silicon are polished by CMP. In today's advanced CMOS process, CMP is used to planarize the surface after STI trench fill and for ILD planarization after metal interconnect gap fill.


Crystal Originated Pits: COP is caused mainly by voids at the wafer surface. While epitaxial wafers are COP free, COP is common with non-epitaxial silicon wafers. COP can have a negative impact on gate oxide integrity. Argon-annealing of wafers have shown a significant reduction of COP.


Chemical Vapor Deposition is a technique to deposit thin films on a silicon wafer. In a CVD process, two or more gaseous materials go through a chemical reaction in a CVD reactor chamber. As a result of chemical reaction, dielectric molecules form and subsequently are deposited on the wafer surface. Common dielectric films deposited by CVD are SiO2, Si3N4, SiON. Many different types of CVD technique are available today, based on reactor type, and process conditions, such as pressure and plasma. These include LPCVD, APCVD, PECVD, HDPCVD and MOCVD.     
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Denuded Zone   

Denuded zone is a thin layer of silicon at the top surface of a wafer that is free of defects and contaminants. It is created after a wafer goes through a “gettering” process. Denuded zone is where the semiconductor devices are formed.


Diluted HF: HF diluted in water typically with a ratio of 100:1 (H2O:HF)


Drain-induced Barrier Lowering: In a short-channel MOSFET, the potential barrier between the source and drain is lowered when drain electric field is high and penetrates toward the source. This effect is called DIBL. DIBL increases off-state leakage current and causes drain-to-source punch-through. DIBL is one of the main limiting factors in the scaling of short-channel transistors.


Deep Level Transient Spectroscopy: Deep level transient spectroscopy measures deep trap levels in semiconductors. The method is based on the capacitance change of a reverse biased diode when deep levels emit their carriers after they are charged by forward bias pulse.


Double-diffused MOS: In N-ch DMOS, channel length is determined by the difference in diffusivity of p-type dopant that forms the channel and n-type dopant that forms the source. The region outside the p-type channel is an n-type drift region. In DMOS, a short channel length can be achieved with a relatively long gate length.

Dual-Gate CMOS (also see CMOS)

In today's advanced CMOS technology, gate poly-silicon for N-ch and P-ch MOSFET is doped in n+ and p+, respectively. This is called dual-gate CMOS. In dual-gate CMOS technology, both N-ch and P-ch transistors operate in a surface channel mode. Surface-channel transistors are less prone to punch-through, and are easier to scale than the buried-channel transistors.


Dynamic Random Access Memory: a charge storage capacitor and an access transistor comprise a DRAM cell. Data is stored in the storage capacitor and is accessed through the access transistor, which is typically an N-ch MOSFET. DRAM cell needs a periodic refreshing to keep the data from being lost due to leakage. Data stored in DRAM is lost when power goes off. Two main types of storage capacitors used in the industry are stacked capacitor and trench capacitor.


Deep Ultraviolet Lithography: DUV refers to a lithography generation that uses DUV light with wavelength of 248nm. DUV light is obtained from KrF excimer laser. The name DUV is used to distinguish it from other generations; i-line with wavelength of 356nm, g-line with wavelength of 436nm or future generation of 193nm and 157nm.    
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Equivalent Oxide Thickness: For high k dielectric, or staked gate oxide, its electrical thickness is converted to the equivalent SiO2 thickness for comparison purposes between different materials.


Erasable Programmable Read Only Memory: In an EPROM memory cell, programming is done electrically by hot carrier injection. Electrons generated by impact ionization tunnel through the tunnel oxide, then are trapped in the floating gate poly-silicon. Erase is performed with shining ultraviolet light on the memory chip, which clears trapped electrons out of the floating gate.


Electrically Erasable Programmable Read Only Memory: In EEPROM, erase is performed electrically byte-by-byte on chip. This electrical erase capability is convenient but the memory cell size is larger than EPROM, and as a result, EEPROM memory has lower density and higher price than EPROM.


Extremely Large Scale Integration: A term used to indicate the level of integration. ELSI refers to a higher level of integration than ULSI. Below ULSI, in a descending order, follow VLSI, LSI, MSI and SSI.


Electro-Migration: Current flow in metal interconnects such as aluminum and copper creates momentum transfer from electron to aluminum or to copper atoms. This causes metal atoms to migrate in the direction opposite to current flow, resulting in an increase in metal resistance. In an extreme situation, voids can form in the metal interconnects as a result of EM. EM is a serious reliability issue for metal interconnects.


Electrical Overstress: refers to an electrical stress on semiconductor devices on a chip that is over the electrical specification limit. Electrical signal overshoots in the input or output pins and ESD (electrostatic discharge) are common examples of EOS.


Electron Beam Lithography: a maskless lithography using electron beams to pattern photoresist.


Electron-beam Projection Lithography


Electrostatic Discharge: When electrostatic charge stored on the human body or machine tools is discharged through a semiconductor chip, it can create damages to the circuits and devices on the chip. This is called ESD damage. Input and output pins of IC chips are vulnerable to ESD damages. Robustness of semiconductor chip against ESD damage is evaluated using test methods based on several ESD models; human body model, charged device model and machine tool model.


Etch Stop Layer: typically a thin SiN film, ESL film is deposited on the wafer after the silicidation process of source, drain and gate poly is complete. ESL provides necessary etch selectivity during subsequent contact etch process.


Extreme Ultraviolet Lithography; EUV is one of the next generation lithography (NGL) candidate technologies. EUV uses a light with wavelength of around 10nm-20nm. EUV LLC is an US industry-government consortium that carries out EUV research.  

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Floating-gate Avalanche MOS: refers to a non-volatile memory cell structure, where electrons are generated by drain avalanche breakdown, then get trapped in the floating gate.


Front-end of the line: usually refers to process steps from wafer start to completion of transistor formation prior to first ILD deposition.

Flash Memory   

A type of nonvolatile memory where charge is stored in the floating gate or at the oxide-nitride interface. Data is preserved even when the power is off. For details, click "Memory", then see Nonvolatile section.


Ferro-electric Random Access Memory


Fourier Transform Infrared Spectroscopy: FTIR detects impurity levels in materials used in semiconductor processing. Infrared spectroscopy is based on transmission and absorption characteristic of excited electrons from impurities in the sample material. With Fourier transformation of signals, a high sensitivity in impurity detection is achieved.


Gate-induced Drain Leakage: a leakage current generated by tunneling of carriers between valence band and conduction band. GIDL occurs at the gate-to-drain overlap region where a high drain voltage causes a large band bending.


Hot Carrier Injection (see HCE, hot carrier effect)


hot carrier effect. Refers to the effect of high energy electrons or holes generated as a result of impact ionization at the drain side of the channel. These hot carriers are subsequently injected into the gate oxide, causing device degradation. HCE is one the key reliability concerns for the short-channel MOSFET's.

Halo Implant   

Halo implant is an implant with a tilt angle used to create a non-uniform channel doping profile in a MOSFET. Halo implant is effective to control the short-channel effect. Today's deep sub-micron transistors typically use halo implant to improve short-channel characteristics.


Heterojunction BJT


High Density Plasma


Hyrdo-peroxide Mixture  
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Integrated Circuits:


Integrated Device Manufacturer, as opposed to fabless company or foundry. IDMs design IC products, produce them in their fabs and sell them to the market under their brand names.


Interlevel Dielectric: dielectric between two different levels of interconnect


Inter-Metal Dielectric: same as ILD


Interuniversity Microelectronic Center: a research organization located in Leuven, Belgium. IMEC perfoms contract research on advanced semiconductor technologies.


International Semiconductor Manufacturing Technology: an industry consortium formed to carry out research projects for the member companies. Formerly SEMATECH, it changed its name to ISMT after it accepted membership from non-U.S. companies.


Junction Field Effect Transistor

Kooi Effect   

Also called the “white ribbon effect”, Kooi effect refers to the phenomena of oxide thinning at the edge of the active area after LOCOS isolation process. According to a model proposed by Kooi, et al., ammonia gas generated during LOCOS oxidation diffuses under silicon nitride LOCOS mask to the Si-SiO2 interface and forms silicon nitride layer at the Si-SiO2 interface near the silicon nitride LOCOS mask edge. Unless this locally nitrided region is completely removed before a subsequent gate oxidation step, a significant oxide thinning can occur in the gate oxide along the edge of the active area.


KrF is a source of an excimer laser that produces high power laser at a wavelength of 248nm.

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Latch up   

Latch up is a self-sustaining low impedance state between the p-type junction and n-type junction in a p-n-p-n structure. This p-n-p-n structure acts as a pair of coupled bipolar junction transistors (one PNP, the other NPN BJT.) Latch up is triggered by forward-biasing one of the p-n junctions that serves as a base-to-emitter junction. Once triggered and if the conditions are met to sustain the latch up, the p-n-p-n structure enters a low impedance state drawing a large current. The latch up is sustained by a positive feedback between the two BJT's. Latch up is a serious concern for CMOS circuits but it can be suppressed by proper layout and process techniques such as using guard rings, use of epi wafer or retrograde wells.


Large Angle Tilt Implanted Drain. A method to form a drain and source junctions of MOSFET using a large angle tilt implant. LATID increases the gate-to-drain overlap, which helps reduce HCI effect.


Local Oxidation of Silicon: device isolation technique used in older generation of technologies before STI was used. Silicon nitride on a wafer surface is patterend, then the wafer undergoes oxidation. Wafer surface area with no nitride on it gets oxidized, forming a thick field oxide there.


Low Pressure CVD


Laterally Diffused MOS   
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Middle of the Line: typically refers to processing steps that forms transistors and silcides


Magnetically Enhanced Reactive Ion Etch


Metal Organic CVD

Moore's Law

Intel co-founder Gordon Moore's observation on technology innovation. According to his observation, the number of transistors on a chip doubles every two years as a result of technology scaling.


MOSFET is for Metal-Oxide-Semiconductor Field-Effect-Transistor. The name is derived from the vertical structure of the transistor. Metal serves as a gate electrode, oxide refers to a thin gate dielectric (silicon dioxide) separating the gate electrode and silicon substrate. MOSFET is a four terminal device: drain, source, gate and substrate. The channel is formed at the gate oxide and silicon substrate interface by the electric field created between the gate and substrate. As a result, current flows between source and drain though the channel. In early days, gate electrode was formed with aluminum, hence the name “metal”. In today's so-called silicon gate technology, poly-silicon is used as a gate electrode. In N-ch MOSFET, electrons flow in the channel while in P-ch MOSFET, holes do.


Magnetoresistive RAM


negative bias thermal instability is caused by hydrogen or water molecule in the gate oxide. With very thin gate gate oxide, NBTI can be a serious problem, especially for P-ch MOSFET. One of the theories for the mechanism of Vt instability under negative bias at high temperature is hole-assisted Si-H or Si-B bond dissociation through electrochemical reaction. Positive fixed charges and donor type interface traps are created as a result.


Next Generation Lithography
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Oxidation Enhanced Diffusion: During oxidation of silicon, silicon intersititials or vacancies are created and these inturn enhance dopant diffusion in  the surrounding area.


Optical Proximity Correction


Plasma Enhanced CVD


Plasma Enhanced TEOS (see also TEOS)


Plasmas induced damage: Deposition and etch processes that rely on high density plasma, such as PECVD, HDP oxide, can create damage to gate dielectrics, causing reliability problems.


Pre-Metal Dielecric


Programmable Read Only Memory


Phase Shift Mask


Random Access Memory


Resolution Enhancement Technique

Retrograde channel (also retro-grade well)

Channel doping profile that decreases in doping level going into the silicon, then increases in doping level deep below the channel surface.


Read Only Memory


reverse short-channel effect: typically refers to an increase of MOSFET threshold voltage (Vt) with decreasing gate length. This is opposite to the conventional short-channel effect, where Vt decreases with decreasing gate length.


Rapid Thermal Anneal


Rapid Thermal Oxidation


Rapid Thermal Processing 
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short-channel effect: refers to the degradation of transistor performance as gate length decreases. A typical short-channel effect is the decrease of Vt with decreasing gate length. This effect is caused by charge sharing between gate and source/drain


Semiconductor Controlled Rectifier


Source Drain Extension: a short overlap region between gate and source or drain. The junction depth of SDE is made smaller than the heavily doped source and drain regions to improve short-channel effect.


Selective Epitaxial Growth

Self-aligned MOSFET

Self-aligned MOSFET refers to the fact that in silicon gate technology, source and drain are self-aligned to the gate, thus eliminating concern for misalignment between active (source/drain) and gate.


An industry consortium formed by U.S. companies. SEMATECH performs advanced research for member companies. Later became ISMT.


Semiconductor Equipment and Material Institute


Soft Error Rate: When an alpha particle hits a memory cell, the stored data can be lost. The rate of this event is called the soft error rate.


Semiconductor Industry Association


Stress-induced Leakage Current


Separation by Implanted Oxide: A method to produce SOI wafer. A high dose oxygen is implanted into a silicon wafer. The wafer then undergoes a high temperture thermal cycle, during which implanted oxygen reacts with silicon forming a buried oxide.


Secondary Ion Mass Spectroscopy: a material composition analysis technique



System-on-a-Chip: An IC chip that contains high density of logic circuit and various types of memory that provides functionality of a large system.


Spin-on Dielectric: see SOG


Spin-on Glass: Spin-on glass: SOG is an oxide film deposited on a wafer during the back end of the process flow to achieve a better planarization of wafer surface. SOG material is a liquid solution containing siloxane or silicate-based monomers dissolved in various kinds of solvents in liquid form. To form SOG film, a wafer is coated with SOG material, and is spun to get thin uniform thickness. After curing of film to a temperature of about 300 to 400C, SiO2 film is formed.


silicon-on-insulator, devices are built in thin Si film lying over the buried oxide. Starting material is either SIMOX or bonded wafer. PDSOI and FDSOI, floating body effect


semiconductor-ONO-semiconductor: A type of non-volatile memory charge storage structure compring poly-silicon gate, ONO film and silicon substrate. Charges injected into the oxide-nitride interface are trapped there then later detrapped by tunneling or carrier recombination, providing program and erase functionality.


Solid Phase Epitaxy


Static Random Access Memory: two CMOS inverters are cross-coupled with two access transistors attached to them. Unlike DRAM, refreshing is not necessary. For details, click "Memory" and see SRAM section.


Spreading Resistance Profiling: A dopant concentration profiling technique that measures spreading resistance as a function of silicon depth, then converts it to the activated dopant concentration in a silicon.


Shallow Trench Isolation: STI is used to isolate devices on a wafer, separating the components so that they do not electrically interfere with one another. In STI process, a stack of thin pad oxide and a SiN film is deposited and patterned, then silicon is etched in the patterned area. Oxidation is then performed to grow a liner oxide over the trench sidewall, followed by filling of trench with deposited oxide. Oxide deposition is typically done by LPCVD or HDP. After trench fill, oxide is polished back by CMP process. STI allows tighter isolation, flatter surface topology and a smaller active area loss than LOCOS. STI is almost exclusively in today's advanced semiconductor process.


Scanning Tunneling Microscope

Strained silicon

Mechanical stress from various sources in a chip causes strain to the silicon crystal lattice. Electron and hole mobility change as a function of magnitude and type of strain. Strained silicon is a promising technique to enhance carrier mobility for sub-100nm technologies.


Process simulation program developed by the researchers at the Stanford University

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Technology Computer Aided Design


Time Dependent Dielectric Breakdown: Gate oxide reliability and lifetime is evaluated using TDDB by applying high electric field to the oxide and observing fail rate as a function of stress time.


Transient Enhanced Diffusion: TED refers to the fact dopants in the silicon wafer diffuses at a much faster rate in very short time at the beginning of thermal cycle.


Transmission Electron Microscope


tetraethylorthosilicate [Si-(OC2H5)4]: TEOS is a material commonly used to deposit oxide film on the wafer. Oxide film deposited by CVD using TEOS offers excellent conformality. It is liquid at room temperature but its gaseous form is used during CVD process


Thin Film Transistor: TFT is formed on a thin polycrytalline film deposited on a dielectric substrate.


Transistor Transistor Logic: Logic IC fabricated with bipolar junction transistors with 5V supply voltage. The name derives from the fact that both pull-up and pull-down devices are transistors. Integration levels range from SSI to MSI.


Ultra Large Scale Integration: A level of integration that is higher than VLSI but lower than ELSI


Ultra Shallow Junction

Van der Pauw

A specially designed test structure which is used to measure sheet resistance of conducting layer


Very Large Scale Integration: A level of integration that is higher than LSI but lower than ULSI


Vertical MOS; VMOS uses preferential etching of (100) silicon to form a V-shaped groove at the surface of a wafer. Drain and source are formed at the top and bottom of the V-groove, with V-groove slope used as a gate.


Wafer Scale Integration: An attempt to build IC on an entire wafer


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Monthly Forum
April 2005

Flash Memory Technology:

Promises and Challenges

May 2005  

Managing Stress in the sub-100nm Era


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