Semiconductor OneSource: Semiconductor Glossary -- Search For : oxide

Term (Index)	Definition
aluminum oxide, alumina, Al2O3	oxide featuring energy gap Eg ~ 5 eV and k ~8; in the form of single-crystal known as sapphire.
sapphire	single-crystal (hexagonal lattice)Al₂O₃; can be synthesized and processed into various shapes including wafers; excellent insulater, highly resistant to most common chemicals and temperature, transparent to the wavelengths from about 0.4 tp about 4 micrometers; used as a substrate in SOS (Silicon-on-Sapphire) technology as well as substrate for other thin-film semiconductors such as GaN.

Term (Index)	Definition
buffered oxide etch, BEO	HF-water solution with ammonium fluoride, NH₄F, added to prevent depletion of fluorine during oxide etching; at 34% NH₄F : 6.8% HF : 58.6% H₂O BEO etches thermal SiO₂ etches at the rate of 100 nm/min.
DHF	dilute HF; SiO₂ etching solution of 49% HF in water; typical mixture: 1 part HF : 100 parts H₂O.

Term (Index)	Definition
buried oxide, BOX	oxide layer in SOI substrates; oxide (SiO₂) buried in silicon wafer at the depth ranging from less than 100 nm to several micrometers from the wafer surface depending on application; thickness of BOX is typically in the range from about 40 nm to about 100 nm.
bonded SOI	SOI substrates formed by bonding two silicon wafers with oxidized surfaces; following bonding one wafer is polished down to the desired thickness of active layer with interface oxide becoming a buried oxide.
SIMOX,	Separation by IMplantation of OXygen; common method used to fabricate SOI substrates; oxygen ions are implanted into Si substrate and form a buried oxide layer.

Term (Index)	Definition
Carbon Doped Oxide, CDO,	an oxide to which carbon is added to reduce its dielectric constant k; used as a low-k interlayer dielectric in advanced interconnection scheme.

Term (Index)	Definition
chemical oxide	oxide growing on silicon surface during wet cleaning and rinsing operations; highly hydrated with composition departing from stoichiometric SiO2 (SiO_x with x<2).

Term (Index)	Definition
dry oxide	thin layer of SiO₂ grown on Si surface by dry oxidation; gate oxides are dry oxides.
dry oxidation	process of thermal oxidation carried out in the moisture-free oxygen.
gate oxide	a layer of very thin oxide sandwiched between semiconductor and gate contact in MOS devices; can be as thin as 1 nm in advance silicon digital integrated circuits and as thick as 70 nm in discrete power MOSFETs; typically thermally grown SiO₂, often nitrided; in ultra-small geometry CMOS ICs SiO₂ can be replaced with dielectrics fetauring higher than SiO₂ dielectric constant.

Term (Index)	Definition
EOT, equivalent oxide thickness	a number used to compare performance of high-k dielectric MOS gates with performance of SiO₂ based MOS gates; shows thickness of SiO₂ gate oxide needed to obtain the same gate capacitance as the one obtained with thicker than SiO₂ dielectric featuring higher dielectric constant k; e.g. EOT of 1 nm would result from the use a 10 nm thick dielectric featuring k=39 (k of SiO₂ is 3.9)

Term (Index)	Definition
field oxide, FOX	relatively thick oxide (typically 100 - 500 nm) formed to passivate and protect semiconductor surface outside of active device area; part of any semiconductor device, but does not participate in device operation.
wet oxidation	thermal oxidation of silicon carried out in water vapor containing oxygen, or in steam; significantly higher oxide growth rate as compared to dry oxidation; used to form relatively thick films of SiO₂ on Si surface; wet oxide contains Si-H and Si-OH, and hence, features inferior to dry oxide electrical integrity.

Term (Index)	Definition
fluorinated oxide	silicon dioxide, SiO₂, with fluorine added to reduce its dielectric constant k; used as a reduced-k inter- layer dielectric (ILD).
low-k dielectric	dielectric material featuring dielectric constant k lower than 3.9 which is k of SiO₂; used to insulate adjacent metal lines (interlayer dielectric, ILD) in advanced integrated circuits; low k reduces undesired capacitive coupling, and hence "cross talk", between lines. Reference: SemiOneSource,Notes

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Definition

gadolinum oxide, Gd2O3,

gadolinia; rare earth metal oxide: adequately meets requirements of an MOS gate dielectric,k-value in the range 10-16, energy gap of 5.4 eV, a high conduction band offset with silicon, low leakage current, high dielectric strength; in the crystalline form cubic lattice ith close match to silicon; of interest because of combination of above listed properties; represents 2nd generation high-k dielectrics.

Term (Index)	Definition
gate oxide	a layer of very thin oxide sandwiched between semiconductor and gate contact in MOS devices; can be as thin as 1 nm in advance silicon digital integrated circuits and as thick as 70 nm in discrete power MOSFETs; typically thermally grown SiO₂, often nitrided; in ultra-small geometry CMOS ICs SiO₂ can be replaced with dielectrics fetauring higher than SiO₂ dielectric constant.
high-k dielectric	dielectric material featuring dielectric constant k higher than 3.9 which is k of SiO₂; used as gate dielectric (amorphous) in MOS devices and in storage capacitors; high k increases capacitance, or keeps in unchanged at the reduced area of MOS gate and gate dielectric sufficiently thick to prevent excessive tunneling current. Reference: See Semiconductor Notes for more information
silicon dioxide, SiO2	silica; native oxide of silicon and at the same time an excellent insulator; the most common insulator in semiconductor device technology, particularly in silicon MOS/CMOS where it is use as a gate oxide; high quality films are obtained by thermal oxidation of silicon; thermal SiO₂ forms smooth, low-defect interface with Si; can be also readily deposited by CVD; SiO₂ performs various functions in silicon device technology which to large degree depends on outstanding characteristics of; also used in non-Si devices; Key parameters: energy gap Eg ~ 8eV, dielectric strength 5-15 x 10⁶ V/cm depending on thickness, dielectric constant k = 3.9, density 2.3 g/cm³, refractive index n =1.46, melting point ~ 1700 ^oC; prone to contamination with alkali ions and sensitive to high energy radiation; in semiconductor technology used in the form amorphous thin films; single crystal SiO₂ is known as quartz.

Term (Index)	Definition
hafnium oxide, HfO2	high-k dielectric considered for next generation MOS gates; dielectric constant k ~25; limited thermal stability with silicon; thermally stable up to 700^oC.
alternative dielectrics	dielectrics featuring dielectric constant k > 3.9 (3.9 is a dielectric constant of SiO₂)and acting as gate oxides in silicon MOS devices instead of SiO₂; referred to as "high-k dielectrics"; also dielectrics featuring dielectric constant k < 3.9 and used as ILD; referred to as "low-k dielectrics".

Term (Index)

Definition

MOS, Metal Oxide Semiconductor

Metal-Oxide-Semiconductor; three-layer structure (typically M-SiO₂-Si)in which concentration of charge carriers in semiconductor's sub-surface region is controlled by potential applied to metal contact or in other words by a field effect; MOS gate can invert sub-surface region of its semiconductor; it works only if no excessive leakage current flows across the oxide; core of the MOS Field Effect Transistors, and hence, CMOS. Also, imaging Charge Coupled Devices (CCD) are based on MOS capacitor structure.

Term (Index)	Definition
native oxide	own oxide of the solid; e.g. SiO₂ is a native oxide of Si, Al₂O₃ is a native oxide of Al, etc.
silicon dioxide, SiO2	silica; native oxide of silicon and at the same time an excellent insulator; the most common insulator in semiconductor device technology, particularly in silicon MOS/CMOS where it is use as a gate oxide; high quality films are obtained by thermal oxidation of silicon; thermal SiO₂ forms smooth, low-defect interface with Si; can be also readily deposited by CVD; SiO₂ performs various functions in silicon device technology which to large degree depends on outstanding characteristics of; also used in non-Si devices; Key parameters: energy gap Eg ~ 8eV, dielectric strength 5-15 x 10⁶ V/cm depending on thickness, dielectric constant k = 3.9, density 2.3 g/cm³, refractive index n =1.46, melting point ~ 1700 ^oC; prone to contamination with alkali ions and sensitive to high energy radiation; in semiconductor technology used in the form amorphous thin films; single crystal SiO₂ is known as quartz.

Term (Index)	Definition
nitric oxide, NO	used in semiconductor processing as a source of atomic nitrogen; highly toxic gas.
ammonia, NH3	toxic gas used in semiconductor processing as a source of atomic nitrogen which can be extracted from ammonia at lower temperature than from molecular nitrogen, N₂.
nitridation	high temperature anneal in nitrogen containing ambient(NO, N₂O or NH₃); typically refers to the process during which nitrogen is added to ultra-thin SiO₂ on Si surface.
nitrous oxide, N2O	nonflammable gas used in semiconductor processing as a source of atomic nitrogen; nontoxic, know as a "laughing gas".

Term (Index)	Definition
nitrided oxide	nitrogen rich silicon dioxide; formed by exposing SiO₂ to nitrogen containing ambient at high temperature or to nitrogen containing plasma.

Term (Index)	Definition
nitrous oxide, N2O	nonflammable gas used in semiconductor processing as a source of atomic nitrogen; nontoxic, know as a "laughing gas".
ammonia, NH3	toxic gas used in semiconductor processing as a source of atomic nitrogen which can be extracted from ammonia at lower temperature than from molecular nitrogen, N₂.
nitridation	high temperature anneal in nitrogen containing ambient(NO, N₂O or NH₃); typically refers to the process during which nitrogen is added to ultra-thin SiO₂ on Si surface.
nitric oxide, NO	used in semiconductor processing as a source of atomic nitrogen; highly toxic gas.

Term (Index)	Definition
oxide breakdown	irriversible change in physical properties of an insulating oxide as a result of very high electric field in the oxide; as a result of "breakdown" oxide no longer displays insulating properties. Reference: See Semiconductor Note #20 for more information
progressive breakdown	gradual degradation, and eventual breakdown, of the very thin gate oxide in MOS devices under the prolonged electric field stress.
hard breakdown	catastrophic, irreversible breakdown of the MOS gate oxide.
soft breakdown	excessive leakage current in the MOS gate oxide, but no irreversible breakdown of the oxide.

Term (Index)	Definition
oxide etching	process causing dissolution of an oxide in a liquid solution, or its volatilization in the gaseous ambient.
hydrofluoric acid, HF	very hazardous acid commonly used in silicon processing to etch silicon dioxide, SiO₂; also, important component of essentially all surface cleaning recipes.
Reactive Ion Etching, RIE	variation of plasma etching in which during etching semiconductor wafer is placed on the RF powered electrode; wafer takes on potential which accelerates etching species extracted from plasma toward the etched surface; chemical etching reaction is preferentially taking place in the direction normal to the surface, i.e. etching is more anisotropic than in plasma etching but is less selective; leaves etched surface damaged; the most common etching mode in semiconductor manufacturing.

Term (Index)	Definition
oxide fixed charge, Qf	charge in Si-SiO₂ structure; located in the oxide in the immediate vicinity of Si surface; does not move and exchange charge with Si, hence, "fixed"; associated with incompletely oxidized silicon or in other words, with excess silicon; lower density at higher temperature of oxidation; can be lowered by post-oxidation anneal in N₂ or Ar; fixed charge alters characteristics of Si-SiO₂ based MOS gate stacks.
dangling bond	unsaturated (broken) interatomic bond at the semiconductor surface; electronically active; can interact with charge carriers in semiconductor.

Term (Index)	Definition
oxide mobile charge, Qm	electrically charged species which can move in the MOS gate oxide under the influence of electric field; causes severe instabilities of MOSFET characteristics, e.g. fluctuations of the threshold voltage V_T; Na⁺ ions are the most common mobile charges in SiO₂.
sodium, Na	alkaline metal; one of the most common element in the environment; sodium ions Na⁺ are very harmful contaminants of SiO₂ in silicon processing; Na⁺ ion can move in SiO₂ under the influence of electric field resulting in instabilities of characteristics of MOS based devices; Na⁺ contamination must be prevented in Si manufacturing environment.
ionic conduction	electrical conduction in an insulator due to ionic rather than electronic motion; slow process featuring high activation energy; example: motion of sodium ions (Na⁺) in SiO₂.

Term (Index)	Definition
oxide trapped charge	charge centers in SiO₂ and other gate dielectrics which are electrically activated/de-activated by trapping/de-trapping charge carriers injected into the oxide either from the gate or from the substrate; causes instabilities of MOSFETs characteristics.
gate injection	during constant-current stress of MOS gate stacks electrons are injected into the oxide from the gate contact.
substrate injection	during constant-current stress of MOS gate stacks electrons are injected into the oxide from the Si substrate.

Term (Index)	Definition
ramp voltage oxide breakdown, Ebd	measure of reliability of oxides in MOS gates; gate voltage is gradually increased until oxide breaks down (uncontrolled current flows across the oxide)and oxide breakdown voltage is determined; a TZDB method; oxide breakdown field is a ratio of breakdown voltage over oxide thickness typically expressed in MV/cm.
oxide breakdown	irriversible change in physical properties of an insulating oxide as a result of very high electric field in the oxide; as a result of "breakdown" oxide no longer displays insulating properties. Reference: See Semiconductor Note #20 for more information
charge-to-breakdown, Qbd	measure of reliability of oxides in MOS gates; certain current is forced through the oxide at the constant gate voltage; point in time at which voltage drops (indicating oxide failure) is determined; knowing current and time to breakdown total charge needed to break the oxide is determined; a TDDB method.
Time-Dependent Dielectric Breakdown, TDDB	technique to evaluate reliability of gate oxides in MOS devices; breakdown of the oxide resulting from the prolonged stress; either time needed to break voltage stressed oxide is measured (CVS - Constant Voltage Stress), or time of current injection into the oxide after which oxide fails (CCS - Constant Current Stress). Reference: Click here for additional information
Time-Zero Dielectric Breakdown, TZDB	technique to evaluate reliability of gate oxides in MOS devices; oxide breakdown occuring without prolonged stress, i.e. under the condition of stress rapidly increasing from zero to oxide breakdown. Reference: Click here for additional information

Term (Index)	Definition
thermal oxidation, thermal oxide	growth of native oxide of the solid through oxidation of solid's surface at elevated temperature; results from chemical reaction of host atoms with oxygen containing ambient; thermal oxidation of silicon results in a very high quality silicon dioxide, SiO₂, formed on the silicon surface; most other semiconductors do not form device quality thermal oxide, hence, term "thermal oxidation" is almost synonymous with "thermal oxidation of silicon". Reference: Thermal oxidation of silicon.
Deal - Grove model	a model describing kinetics of thermal oxidation of silicon based on chemical reaction between silicon and oxidizing species; most accurate for oxides thicker than about 30 nm; of limited use for oxide thinner than about 10 nm; assumes surface reaction controlled oxide growth in early stage of oxidation (linear regime) and controlled by diffusion of oxidizing species through the oxide during extended oxidation (parabolic regime); one among the best established models in silicon processing.

Term (Index)	Definition
titanium oxide, TiO3	dielectric material featuring dielectric constant k=20-85 ("high-k" dielectric); not thermally stable with silicon, and hence, not used as a high-k dielectric for MOS gates.
high-k dielectric	dielectric material featuring dielectric constant k higher than 3.9 which is k of SiO₂; used as gate dielectric (amorphous) in MOS devices and in storage capacitors; high k increases capacitance, or keeps in unchanged at the reduced area of MOS gate and gate dielectric sufficiently thick to prevent excessive tunneling current. Reference: See Semiconductor Notes for more information

Term (Index)	Definition
tunnel oxide	oxide in MOS structures so thin that the probability of electron direct tunneling across it (i.e. between metal gate and semiconductor) is very high; in the case of Si-SiO₂ based MOS devices significant direct tunneling current is observed for oxides typically less than about 3.0 nm.
direct tunneling	tunneling in MOS structures with ultra-thin oxide (< 4 nm) during which electrons from the conduction band in semiconductor are transferred across the oxide directly (i.e. without changing energy) into the conduction band of metal; probability of direct tunneling is a very strong function of the width of the barrier electron tunnels through (oxide thickness in MOS devices)
tunneling, tunneling current	transport of electron across the potential barrier without changing its energy; as opposed to electron transport "over" the barrier (thermionic emission) in which case its energy is must be changed; tunneling probability is a strong function of the width ofpotential barrier; examples: tunneling across the potential barrier at the metal-semiconductor contact, or across the potential barrier at the p-n junction, or across an oxide (direct tunneling for oxide thinner than about 3 nm, Fowler-Nordheim tunneling for oxide 5-10 nm thick) in MOS structure.
gate oxide	a layer of very thin oxide sandwiched between semiconductor and gate contact in MOS devices; can be as thin as 1 nm in advance silicon digital integrated circuits and as thick as 70 nm in discrete power MOSFETs; typically thermally grown SiO₂, often nitrided; in ultra-small geometry CMOS ICs SiO₂ can be replaced with dielectrics fetauring higher than SiO₂ dielectric constant.

Term (Index)	Definition
ultra-thin oxide	oxide thin enough to allow substantial direct tunneling current between metal gate and semiconductor substrate in MOS devices; typically thinner than 3 nm.
tunnel oxide	oxide in MOS structures so thin that the probability of electron direct tunneling across it (i.e. between metal gate and semiconductor) is very high; in the case of Si-SiO₂ based MOS devices significant direct tunneling current is observed for oxides typically less than about 3.0 nm.

Term (Index)	Definition
zinc oxide, ZnO	wide bandgap AII-BVI semiconductor; E_g=3.4 eV, direct; possible blue and violet emission and UV detection; due to the Wurtzite lattice structure and similar lattice constant to GaN can be used as a substrate for GaN (lattice matched to InGaN with 22% In content); a rare case of a solid displaying semiconductor and piezoelectric properties.
direct bandgap semiconductor	semiconductor in which the bottom of the conduction band and the top of the valence band occur at the momentum k=0;in the case of d.b.s. energy released during band-to-band electron recombination with a hole is converted primarily into radiation (radiant recombination); wavelength of emitted radiation is determined by the energy gap of semiconductor; examples of d.b.s. GaAs, InP, etc.
wide bandgap semiconductor	semiconductor featuring energy gap E_g > 2.5 eV (rather arbitrary criterion), useful in high temperature applications and emission of blue radiation (should feature direct bandgap at the same time); e.g. SiC (E_g = 2.9 eV), GaN (E_g = 3.5 eV), ZnS (E_g = 3.68 eV)

Term (Index)	Definition
zirconuim oxide, zirconia, ZrO2	dielectric featuring dielectric constant k in the range of 20-25; thermodynamically stable with silicon but tends to crystallize at about 700 ^o; considered as an alternative gate dielectric for next generation MOS technology.
alternative dielectrics	dielectrics featuring dielectric constant k > 3.9 (3.9 is a dielectric constant of SiO₂)and acting as gate oxides in silicon MOS devices instead of SiO₂; referred to as "high-k dielectrics"; also dielectrics featuring dielectric constant k < 3.9 and used as ILD; referred to as "low-k dielectrics".
hafnium oxide, HfO2	high-k dielectric considered for next generation MOS gates; dielectric constant k ~25; limited thermal stability with silicon; thermally stable up to 700^oC.
hafnium silicate, HfSiO4	high-k dielectric considered for next generation MOS gates, k~15-18; thermodynamically stable with silicon.
zirconium silicate, ZrSiO4	dielectric material featuring dielectric constant about 15; thermodynamically stable with Si; in contact with Si combines characteristics of silicon dioxide,SiO₂,and zirconium oxide, ZrO₂; considered to be among prime candidates for a gate dielectric in next generation CMOS devices.
gate oxide	a layer of very thin oxide sandwiched between semiconductor and gate contact in MOS devices; can be as thin as 1 nm in advance silicon digital integrated circuits and as thick as 70 nm in discrete power MOSFETs; typically thermally grown SiO₂, often nitrided; in ultra-small geometry CMOS ICs SiO₂ can be replaced with dielectrics fetauring higher than SiO₂ dielectric constant.