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High-κ Dielectric
The term high-κ dielectric refers to a material with a high dielectric constant (κ, kappa), as compared to silicon dioxide. High-κ dielectrics are used in semiconductor manufacturing processes where they are usually used to replace a silicon dioxide gate dielectric or another dielectric layer of a device. The implementation of high-κ gate dielectrics is one of several strategies developed to allow further miniaturization of microelectronic components, colloquially referred to as extending Moore's Law. Sometimes these materials are called "high-k" (pronounced "high kay"), instead of "high-κ" (high kappa). Need for high-κ materials Silicon dioxide () has been used as a gate oxide material for decades. As metal-oxide-semiconductor field-effect transistors (MOSFETs) have decreased in size, the thickness of the silicon dioxide gate dielectric has steadily decreased to increase the gate capacitance (per unit area) and thereby drive current (per device width), raising device perfor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dielectric Constant
The relative permittivity (in older texts, dielectric constant) is the permittivity of a material expressed as a ratio with the electric permittivity of a vacuum. A dielectric is an insulating material, and the dielectric constant of an insulator measures the ability of the insulator to store electric energy in an electrical field. Permittivity is a material's property that affects the Coulomb force between two point charges in the material. Relative permittivity is the factor by which the electric field between the charges is decreased relative to vacuum. Likewise, relative permittivity is the ratio of the capacitance of a capacitor using that material as a dielectric, compared with a similar capacitor that has vacuum as its dielectric. Relative permittivity is also commonly known as the dielectric constant, a term still used but deprecated by standards organizations in engineering as well as in chemistry. Definition Relative permittivity is typically denoted as (sometimes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vacuum Permittivity
Vacuum permittivity, commonly denoted (pronounced "epsilon nought" or "epsilon zero"), is the value of the absolute dielectric permittivity of classical vacuum. It may also be referred to as the permittivity of free space, the electric constant, or the distributed capacitance of the vacuum. It is an ideal (baseline) physical constant. Its CODATA value is: : ( farads per meter), with a relative uncertainty of It is a measure of how dense of an electric field is "permitted" to form in response to electric charges, and relates the units for electric charge to mechanical quantities such as length and force. For example, the force between two separated electric charges with spherical symmetry (in the vacuum of classical electromagnetism) is given by Coulomb's law: :F_\text = \frac \frac Here, ''q''1 and ''q''2 are the charges, ''r'' is the distance between their centres, and the value of the constant fraction 1/4 \pi \varepsilon_0 (known as the Coulomb constant, ''k''e) is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dark Current Spectroscopy
Dark current spectroscopy is a technique that is used to determine contaminants in silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab .... References Silicon Semiconductor device fabrication {{science-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atomic Layer Deposition
Atomic layer deposition (ALD) is a thin-film deposition technique based on the sequential use of a gas-phase chemical process; it is a subclass of chemical vapour deposition. The majority of ALD reactions use two chemicals called precursors (also called "reactants"). These precursors react with the surface of a material one at a time in a sequential, self-limiting, manner. A thin film is slowly deposited through repeated exposure to separate precursors. ALD is a key process in fabricating semiconductor devices, and part of the set of tools for synthesising nanomaterials. Introduction During atomic layer deposition a film is grown on a substrate by exposing its surface to alternate gaseous species (typically referred to as precursors or reactants). In contrast to chemical vapor deposition, the precursors are never present simultaneously in the reactor, but they are inserted as a series of sequential, non-overlapping pulses. In each of these pulses the precursor molecules react wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zirconium Dioxide
Zirconium dioxide (), sometimes known as zirconia (not to be confused with zircon), is a white crystalline oxide of zirconium. Its most naturally occurring form, with a monoclinic crystalline structure, is the mineral baddeleyite. A dopant stabilized cubic structured zirconia, cubic zirconia, is synthesized in various colours for use as a gemstone and a diamond simulant. Production, chemical properties, occurrence Zirconia is produced by calcining zirconium compounds, exploiting its high thermostability.Ralph Nielsen "Zirconium and Zirconium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. Structure Three phases are known: monoclinic below 1170 °C, tetragonal between 1170 °C and 2370 °C, and cubic above 2370 °C. The trend is for higher symmetry at higher temperatures, as is usually the case. A small percentage of the oxides of calcium or yttrium stabilize in the cubic phase. The very rare mineral tazheranite, , ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hafnium Dioxide
Hafnium(IV) oxide is the inorganic compound with the formula . Also known as hafnium dioxide or hafnia, this colourless solid is one of the most common and stable compounds of hafnium. It is an electrical insulator with a band gap of 5.3~5.7 eV. Hafnium dioxide is an intermediate in some processes that give hafnium metal. Hafnium(IV) oxide is quite inert. It reacts with strong acids such as concentrated sulfuric acid and with strong bases. It dissolves slowly in hydrofluoric acid to give fluorohafnate anions. At elevated temperatures, it reacts with chlorine in the presence of graphite or carbon tetrachloride to give hafnium tetrachloride. Structure Hafnia typically adopts the same structure as zirconia (ZrO2). Unlike TiO2, which features six-coordinate Ti in all phases, zirconia and hafnia consist of seven-coordinate metal centres. A variety of other crystalline phases have been experimentally observed, including cubic fluorite (Fmm), tetragonal (P42/nmc), monoclinic (P21/c) an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zirconium Silicate
Zirconium silicate, also zirconium orthosilicate, ZrSiO4, is a chemical compound, a silicate of zirconium. It occurs in nature as zircon, a silicate mineral. Powdered zirconium silicate is also known as zircon flour. Zirconium silicate is usually colorless, but impurities induce various colorations. It is insoluble in water, acids, alkali and aqua regia. Hardness is 7.5 on the Mohs scale. Structure and bonding Zircon consists of 8-coordinated Zr4+ centers linked to tetrahedral orthosilicate SiO44- sites. The oxygen atoms are all triply bridging, each with the environment OZr2Si. Given its highly crosslinked structure, the material is hard, and hence prized as gemstone and abrasive. Zr(IV) is a d0 ion. Consequently the material is colorless and diamagnetic. Production Zirconium silicate occurs in nature as mineral zircon. Concentrated sources of zircon are rare. It is mined from sand deposits and separated by gravity. Some sands contain a few percent of zircon. It can al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hafnium Silicate
Hafnium silicate is the hafnium(IV) salt of silicic acid with the chemical formula of HfSiO4. Thin films of hafnium silicate and zirconium silicate grown by atomic layer deposition, chemical vapor deposition or MOCVD, can be used as a high-k dielectric as a replacement for silicon dioxide in modern semiconductor devices. The addition of silicon to hafnium oxide increases the band gap, while decreasing the dielectric constant. Furthermore, it increases the crystallization temperature of amorphous films and further increases the material's thermal stability with Si at high temperatures. Nitrogen is sometimes added to hafnium silicate for improving the thermal stability and electrical properties of devices. Natural occurrence Hafnon is the natural form of hafnium orthosilicate. Its name suggests the mineral is the Hf analogue of much more common zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron Mobility
In solid-state physics, the electron mobility characterises how quickly an electron can move through a metal or semiconductor when pulled by an electric field. There is an analogous quantity for holes, called hole mobility. The term carrier mobility refers in general to both electron and hole mobility. Electron and hole mobility are special cases of electrical mobility of charged particles in a fluid under an applied electric field. When an electric field ''E'' is applied across a piece of material, the electrons respond by moving with an average velocity called the drift velocity, v_d. Then the electron mobility ''μ'' is defined as v_d = \mu E. Electron mobility is almost always specified in units of cm2/( V⋅ s). This is different from the SI unit of mobility, m2/( V⋅ s). They are related by 1 m2/(V⋅s) = 104 cm2/(V⋅s). Conductivity is proportional to the product of mobility and carrier concentration. For example, the same conductivity could come from a small numbe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electronic Band Structure
In solid-state physics, the electronic band structure (or simply band structure) of a solid describes the range of energy levels that electrons may have within it, as well as the ranges of energy that they may not have (called ''band gaps'' or ''forbidden bands''). Band theory derives these bands and band gaps by examining the allowed quantum mechanical wave functions for an electron in a large, periodic lattice of atoms or molecules. Band theory has been successfully used to explain many physical properties of solids, such as electrical resistivity and optical absorption, and forms the foundation of the understanding of all solid-state devices (transistors, solar cells, etc.). Why bands and band gaps occur The electrons of a single, isolated atom occupy atomic orbitals each of which has a discrete energy level. When two or more atoms join together to form a molecule, their atomic orbitals overlap and hybridize. Similarly, if a large number ''N'' of identical atoms come ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Oxidation
In microfabrication, thermal oxidation is a way to produce a thin layer of oxide (usually silicon dioxide) on the surface of a wafer. The technique forces an oxidizing agent to diffuse into the wafer at high temperature and react with it. The rate of oxide growth is often predicted by the Deal–Grove model. Thermal oxidation may be applied to different materials, but most commonly involves the oxidation of silicon substrates to produce silicon dioxide. The chemical reaction Thermal oxidation of silicon is usually performed at a temperature between 800 and 1200 °C, resulting in so called High Temperature Oxide layer (HTO). It may use either water vapor (usually UHP steam) or molecular oxygen as the oxidant; it is consequently called either ''wet'' or ''dry'' oxidation. The reaction is one of the following: :\rm Si + 2H_2O \rightarrow SiO_2 + 2H_ :\rm Si + O_2 \rightarrow SiO_2 \, The oxidizing ambient may also contain several percent of hydrochloric acid (HCl). The chlori ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subthreshold Conduction
Subthreshold conduction or subthreshold leakage or subthreshold drain current is the current between the source and drain of a MOSFET when the transistor is in subthreshold region, or weak-inversion region, that is, for gate-to-source voltages below the threshold voltage. The amount of subthreshold conduction in a transistor is set by its threshold voltage, which is the minimum gate voltage required to switch the device between ''on'' and ''off'' states. However, as the drain current in a MOS device varies exponentially with gate voltage, the conduction does not immediately become zero when the threshold voltage is reached. Rather it continues showing an exponential behavior with respect to the subthreshold gate voltage. When plotted against the applied gate voltage, this subthreshold drain current exhibits a log-linear slope, which is defined as the subthreshold slope. Subthreshold slope is used as a figure of merit for the switching efficiency of a transistor.''Physics of Semi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
