DC plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus.

Chemical vapor deposition (CVD) is a chemical process used to produce high-purity, high-performance solid materials. The process is often used in the semiconductor industry to produce thin films. In a typical CVD process, the wafer (substrate) is exposed to one or more volatile precursors, which react and/or decompose on the substrate surface to produce the desired deposit. Frequently, volatile byproducts are also produced, which are removed by gas flow through the reaction chamber. Image File history File links Download high resolution version (1200x1600, 421 KB) DC-PECVD system in action. ... Image File history File links Download high resolution version (1200x1600, 421 KB) DC-PECVD system in action. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ... A Plasma lamp In physics and chemistry, a plasma is an ionized gas, and is usually considered to be a distinct phase of matter. ... 3D model of three types of single-walled carbon nanotubes. ... A chemical substance is any material substance used in or obtained by a process in chemistry: A chemical compound is a substance consisting of two or more chemical elements that are chemically combined in fixed proportions. ... The semiconductor industry is the collection of business firms engaged in the design and fabrication of semiconductor devices. ... Thin films are material layers of about 1 µm thickness. ... It has been suggested that Wafer prober be merged into this article or section. ... Vapours of hydrogen chloride in a beaker and ammonia in a test tube meet to form a cloud of a new substance, ammonium chloride A chemical reaction is a process that results in the interconversion of chemical substances. ... Chemical decomposition or analysis is the fragmentation of a chemical compound into elements or smaller compounds. ... A by-product is a secondary or incidental product deriving from a manufacturing process or chemical reaction, and is not the primary product or service being produced. ...

Microfabrication processes widely use CVD to deposit materials in various forms, including: monocrystalline, polycrystalline, amorphous, and epitaxial. These materials include: silicon, carbon fiber, carbon nanofibers, filaments, carbon nanotubes, SiO₂, silicon-germanium, tungsten, silicon carbide, silicon nitride, silicon oxynitride, titanium nitride, and various high-k dielectrics. The CVD process is also used to produce synthetic diamonds. Microfabrication is the collective term for the technologies used to fabricate components on a micrometer-sized scale. ... Quartz crystal In chemistry and mineralogy, a crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... ]]s are polycrystalline. ... An amorphous solid is a solid in which there is no long-range order of the positions of the atoms. ... Epitaxy is the growth of crystals of one material on the crystal face of another (heteroepitaxy) or the same (homoepitaxy) material, such that the two materials have a defined relative structural orientation. ... It has been suggested that Silicons ranking be merged into this article or section. ... Carbon fiber composite is a strong, light and very expensive material. ... Carbon nanofibers Carbon nanofibers are cylindric nanostructures with graphene layers arranged as stacked cones, cups or plates. ... A filament is a fine, thinly spun thread, fiber, or wire. ... 3D model of three types of single-walled carbon nanotubes. ... R-phrases R42 R43 R49 S-phrases S22 S36 S37 S45 S53 Flash point non-flammable Supplementary data page Structure and properties n, εr, etc. ... SiGe is the alloy of silicon and germanium. ... General Name, Symbol, Number tungsten, W, 74 Chemical series transition metals Group, Period, Block 6, 6, d Appearance grayish white, lustrous Standard atomic weight 183. ... Silicon carbide (SiC) is a ceramic compound of silicon and carbon that is manufactured on a large scale for use mainly as an abrasive but also occurs in nature as the extremely rare mineral moissanite. ... Silicon nitride (Si3N4) is hard, solid substance, that can be obtained by direct reaction between silicon and nitrogen in high temperatures. ... TiN coated drill Dark gray TiCN coating on a Gerber pocketknife Titanium nitride (TiN) is an extremely hard (~85 Rockwell C Hardness or ~2500 Vickers Hardness)1, ceramic material, often used as a coating on titanium alloy, steel, carbide, and aluminum components to improve the substrates surface properties. ... The term high-κ dielectric refers to materials with a high dielectric constant (κ) (relative to silicon dioxide) which are going to be used [1] in next generation semiconductor components to replace the SiO2 gate dielectric, especially for the low standby power (LSTP) applications at the 45 nm technology node. ... A colourless synthetic diamond produced via chemical vapour deposition Synthetic diamond is diamond produced through chemical or physical processes in a factory. ...

Types of chemical vapor deposition

A number of forms of CVD are in wide use and are frequently referenced in the literature. These processes differ in the means by which chemical reactions are initiated (e.g., activation process) and process conditions.

• Classified by operating pressure
  • Atmospheric pressure CVD (APCVD) - CVD processes at atmospheric pressure.
  • Low-pressure CVD (LPCVD) - CVD processes at subatmospheric pressures. Reduced pressures tend to reduce unwanted gas-phase reactions and improve film uniformity across the wafer. Most modern CVD process are either LPCVD or UHVCVD.
  • Ultrahigh vacuum CVD (UHVCVD) - CVD processes at a very low pressure, typically below 10^-6 Pa (~ 10^-8 torr). Caution: in other fields, a lower division between high and ultra-high vacuum is common, often 10^-7 Pa.
• Classified by physical characteristics of vapor
  • Aerosol assisted CVD (AACVD) - A CVD process in which the precursors are transported to the substrate by means of a liquid/gas aerosol, which can be generated ultrasonically. This technique is suitable for use with involatile precursors.
  • Direct liquid injection CVD (DLICVD) - A CVD process in which the precursors are in liquid form (liquid or solid dissolved in a convenient solvent). Liquid solutions are injected in a vaporization chamber towards injectors (typically car injectors). Then the precursors vapours are transported to the substrate as in classical CVD process. This technique is suitable for use on liquid or solid precursors. High growth rates can be reached using this technique.
• Plasma methods (see also Plasma processing)
  • Microwave plasma-assisted CVD (MPCVD)
  • Plasma-Enhanced CVD (PECVD) - CVD processes that utilize a plasma to enhance chemical reaction rates of the precursors. PECVD processing allows deposition at lower temperatures, which is often critical in the manufacture of semiconductors.
  • Remote plasma-enhanced CVD (RPECVD) - Similar to PECVD except that the wafer substrate is not directly in the plasma discharge region. Removing the wafer from the plasma region allows processing temperatures down to room temperature.
• Atomic layer CVD (ALCVD) – Deposits successive layers of different substances to produce layered, crystalline films. See Atomic layer epitaxy.
• Hot wire CVD (HWCVD) - Also known as Catalytic CVD (Cat-CVD) or hot filament CVD (HFCVD). Uses a hot filament to chemically decompose the source gases.^[1]
• Metalorganic chemical vapor deposition (MOCVD) - CVD processes based on metalorganic precursors.
• Rapid thermal CVD (RTCVD) - CVD processes that use heating lamps or other methods to rapidly heat the wafer substrate. Heating only the substrate rather than the gas or chamber walls helps reduce unwanted gas phase reactions that can lead to particle formation.
• Vapor phase epitaxy (VPE)

The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ... For the standard botanical author abbreviation Torr. ... Ultra high vacuum (UHV) is the regime of characterised by pressures lower than about 10-7 Pascal or 100 nanopascals (~10-9 torr). ... Plasma processing is a plasma-based material processing technology that aims at modifying the chemical and physical properties of a surface. ... Plasma Enhanced Chemical Vapor Deposition (PECVD) is a process mainly to deposit thin films from a gas state (vapor) to a solid state on some substrate. ... A plasma lamp, illustrating some of the more complex phenomena of a plasma, including filamentation. ... Quartz crystal Synthetic bismuth hopper crystal Insulin crystals Gallium, a metal that easily forms large single crystals A huge monocrystal of potassium dihydrogen phosphate grown from solution by Saint-Gobain for the megajoule laser of CEA. In chemistry and mineralogy, a crystal is a solid in which the constituent atoms... It has been suggested that this article or section be merged into Atomic layer deposition. ... Metalorganic chemical vapor deposition (MOCVD) is a chemical vapor deposition process that uses metalorganic source gases. ... It has been suggested that Organometallic compounds be merged into this article or section. ... It has been suggested that Wafer prober be merged into this article or section. ... Particle (ecology) is the term for small objects of nonbiological kind. ... Epitaxy is the growth of crystals of one material on the crystal face of another (heteroepitaxy) or the same (homoepitaxy) material, such that the two materials have a defined relative structural orientation. ...

Substances commonly deposited for ICs

This section discusses the CVD processes often used for integrated circuits (ICs). Particular materials are deposited best under particular conditions. An integrated circuit (IC) is a thin chip consisting of at least two interconnected semiconductor devices, mainly transistors, as well as passive components like resistors. ...

Polysilicon

Polycrystalline silicon is deposited from silane (SiH₄), using the following reaction: ]]s are polycrystalline. ... It has been suggested that Silicons ranking be merged into this article or section. ... Silane is a chemical compound with chemical formula SiH4. ...

SiH₄ → Si + 2H₂

This reaction is usually performed in LPCVD systems, with either pure silane feedstock, or a solution of silane with 70-80% nitrogen. Temperatures between 600 and 650 °C and pressures between 25 and 150 Pa yield a growth rate between 10 and 20 nm per minute. An alternative process uses a hydrogen-based solution. The hydrogen reduces the growth rate, but the temperature is raised to 850 or even 1050 degrees Celsius to compensate. General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). ... A nanometre (American spelling: nanometer, symbol nm) is a unit of length in the metric system, equal to one thousand-millionth of a metre, which is the current SI base unit of length. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ...

Polysilicon may be grown directly with doping, if gases such as phosphine, arsine or diborane are added to the CVD chamber. Diborane increases the growth rate, but arsine and phosphine decrease it. Phosphine is the common name for phosphorus hydride (PH3), also known by the IUPAC name phosphane and, occasionally, phosphamine. ... Arsine, the simplest compound of arsenic, is AsH3. ... Diborane is a colorless gas at room temperature with a repulsive, sweet odor. ...

Silicon dioxide

Silicon dioxide (usually called simply "oxide" in the semiconductor industry) may be deposited by several different processes. Common source gases include silane and oxygen, dichlorosilane (SiCl₂H₂) and nitrous oxide (N₂O), or tetraethylorthosilicate (TEOS; Si(OC₂H₅)₄). The reactions are as follows: R-phrases R42 R43 R49 S-phrases S22 S36 S37 S45 S53 Flash point non-flammable Supplementary data page Structure and properties n, εr, etc. ... Silane is a chemical compound with chemical formula SiH4. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... Dichlorosilane (H2SiCl2), or DCS as it is commonly known, is usually mixed with ammonia (NH3) in LPCVD chambers to grow silicon nitride in semiconductor processing. ... R-phrases S-phrases Supplementary data page Structure and properties n, εr, etc. ... Tetraethyl orthosilicate is the major chemical compound with the formula Si(OC2H5)4. ...

SiH₄ + O₂ → SiO₂ + 2H₂

SiCl₂H₂ + 2N₂O → SiO₂ + 2N₂ + 2HCl

Si(OC₂H₅)₄ → SiO₂ + byproducts

The choice of source gas depends on the thermal stability of the substrate; for instance, aluminium is sensitive to high temperature. Silane deposits between 300 and 500 °C, dichlorosilane at around 900 °C, and TEOS between 650 and 750 °C. However, silane produces a lower-quality oxide than the other methods (lower dielectric strength, for instance), and it deposits nonconformally. Any of these reactions may be used in LPCVD, but the silane reaction is also done in APCVD. CVD oxide invariably has lower quality than thermal oxide, but thermal oxidation can only be used in the earliest stages of IC manufacturing. General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Standard atomic weight 26. ... In physics, the term dielectric strength has the following meanings: Of an insulating material, the maximum electric field strength that it can withstand intrinsically without breaking down, , without experiencing failure of its insulating properties. ... A film that coats a surface is said to be conformal if it has the same thickness on all surfaces. ... In microfabrication, thermal oxidation is a way to produce a thin layer of oxide (usually silicon dioxide) on the surface of a wafer (semiconductor). ...

Oxide may also be grown with impurities (alloying or "doping"). This may have two purposes. During further process steps that occur at high temperature, the impurities may diffuse from the oxide into adjacent layers (most notably silicon) and dope them. Oxides containing 5% to 15% impurities by mass are often used for this purpose. In addition, silicon dioxide alloyed with phosphorus pentoxide ("P-glass") can be used to smooth out uneven surfaces. P-glass softens and reflows at temperatures above 1000 °C. This process requires a phosphorus concentration of at least 6%, but concentrations above 8% can corrode aluminium. Phosphorus is deposited from phosphine gas and oxygen: An alloy is a homogeneous mixture of two or more elements, at least one of which is a metal, and where the resulting material has metallic properties. ... In semiconductor production, doping refers to the process of intentionally introducing impurities into an extremely pure (also referred to as intrinsic) semiconductor in order to change its electrical properties. ... Phosphorus pentoxide, perhaps more accurately diphosphorus pentoxide, is so called because of its empirical formula P2O5, as should be expected of any element in oxidation number +5. ... Phosphine is the common name for phosphorus hydride (PH3), also known by the IUPAC name phosphane and, occasionally, phosphamine. ...

4PH₃ + 5O₂ → 2P₂O₅ + 6H₂

Glasses containing both boron and phosphorus (borophosphosilicate glass, BPSG) undergo viscous flow at lower temperatures; around 850 °C is achievable with glasses containing around 5 weight % of both constituents, but stability in air can be difficult to achieve. Phosphorus oxide in high concentrations interacts with ambient moisture to produce phosphoric acid. Crystals of BPO₄ can also precipitate from the flowing glass on cooling; these crystals are not readily etched in the standard reactive plasmas used to pattern oxides, and will result in circuit defects in integrated circuit manufacturing.

Besides these intentional impurities, CVD oxide may contain byproducts of the deposition process. TEOS produces a relatively pure oxide, whereas silane introduces hydrogen impurities, and dichlorosilane introduces chlorine. General Name, Symbol, Number chlorine, Cl, 17 Chemical series halogens Group, Period, Block 17, 3, p Appearance yellowish green Standard atomic weight 35. ...

Lower temperature deposition of silicon dioxide and doped glasses from TEOS using ozone rather than oxygen has also been explored (350 to 500 °C). Ozone glasses have excellent conformality but tend to be hygroscopic -- that is, they absorb water from the air due to the incorporation of silanol (Si-OH) in the glass. Infrared spectroscopy and mechanical strain as a function of temperature are valuable diagnostic tools for diagnosing such problems.

Silicon nitride

Silicon nitride is often used as an insulator and chemical barrier in manufacturing ICs. The following two reactions deposit nitride from the gas phase: Silicon nitride (Si3N4) is hard, solid substance, that can be obtained by direct reaction between silicon and nitrogen in high temperatures. ...

3SiH₄ + 4NH₃ → Si₃N₄ + 12H₂

3SiCl₂H₂ + 4NH₃ → Si₃N₄ + 6HCl + 6H₂

Silicon nitride deposited by LPCVD contains up to 8% hydrogen. It also experiences strong tensile stress (physics), which may crack films thicker than 200 nm. However, it has higher resistivity and dielectric strength than most insulators commonly available in microfabrication (10¹⁶ Ω·cm and 10 MV/cm, respectively). Stress is the internal distribution of force per unit area that balances and reacts to external loads applied to a body. ... Electrical resistivity (also known as specific electrical resistance) is a measure of how strongly a material opposes the flow of electric current. ... A multimeter can be used to measure resistance in ohms. ... A centimetre (American spelling centimeter, symbol cm) is a unit of length that is equal to one hundredth of a metre, the current SI base unit of length. ... Josephson junction array chip developed by NIST as a standard volt. ...

Another two reactions may be used in plasma to deposit SiNH:

2SiH₄ + N₂ → 2SiNH + 3H₂

SiH₄ + NH₃ → SiNH + 3H₂

These films have much less tensile stress, but worse electrical properties (resistivity 10⁶ to 10¹⁵ Ω·cm, and dielectric strength 1 to 5 MV/cm).

Metals

Some metals (notably aluminium and copper) are seldom or never deposited by CVD. As of 2002, a viable CVD process for copper did not exist, and the metal was deposited by electroplating. Aluminium can be deposited from tri-isobutyl aluminium, but physical vapor deposition methods are usually preferred. General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Standard atomic weight 26. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic pinkish red Standard atomic weight 63. ... 2002 is a common year starting on Tuesday of the Gregorian calendar. ... Electroplating is the process of using Davd lloyd current to coat an electrically conductive object with a relatively thin layer of metal. ... Isobutyl (Common Name) or 2-Methylpropyl (IUPAC) is a substituent group with the formula C4H9. ... Physical vapor deposition (PVD) is a technique used to deposit thin films of various materials onto various surfaces (e. ...

However, CVD processes for molybdenum, tantalum, titanium and tungsten are widely used. These metals can form useful silicides when deposited onto silicon. Mo, Ta and Ti are deposited by LPCVD, from their pentachlorides. In general, for an arbitrary metal M, the reaction is as follows: General Name, Symbol, Number molybdenum, Mo, 42 Chemical series transition metals Group, Period, Block 6, 5, d Appearance gray metallic Standard atomic weight 95. ... General Name, Symbol, Number tantalum, Ta, 73 Chemical series transition metals Group, Period, Block 5, 6, d Appearance gray blue Standard atomic weight 180. ... General Name, Symbol, Number titanium, Ti, 22 Chemical series transition metals Group, Period, Block 4, 4, d Appearance silvery metallic Standard atomic weight 47. ... General Name, Symbol, Number tungsten, W, 74 Chemical series transition metals Group, Period, Block 6, 6, d Appearance grayish white, lustrous Standard atomic weight 183. ... A silicide is a compound that has silicon with more electropositive elements. ...

2MCl₅ + 5H₂ → 2M + 10HCl

The usual source for tungsten is tungsten hexafluoride, which may be deposited in two ways: Tungsten hexafluoride (WF6) is the heaviest known gas. ...

WF₆ → W + 3F₂

WF₆ + 3H₂ → W + 6HF

See also

• Atomic Layer Deposition, a more precise and conformal coating technology
• Physical vapor deposition, the deposition of materials from vapor without chemical reactions

To meet Wikipedias quality standards, this article or section may require cleanup. ... Physical vapor deposition (PVD) is a technique used to deposit thin films of various materials onto various surfaces (e. ...

References

1. ^ Schropp, R.E.I.; B. Stannowski, A.M. Brockhoff, P.A.T.T. van Veenendaal and J.K. Rath. "Hot wire CVD of heterogeneous and polycrystalline silicon semiconducting thin films for application in thin film transistors and solar cells" (PDF). Materials Physics and Mechanics: 73–82. 

• Jaeger, Richard C. (2002). "Film Deposition", Introduction to Microelectronic Fabrication. Upper Saddle River: Prentice Hall. ISBN 0-201-44494-7. 
• Smith, Donald (1995). Thin-Film Deposition: Principles and Practice. MacGraw-Hill. 
• Dobkin and Zuraw (2003). Principles of Chemical Vapor Deposition. Kluwer. 
• ISO 3529/1-1981 Vacuum Technology - Vocabulary - part 1: General terms As quoted by UK National Physical Laboratory

Weblinks

• Fundamental of Chemical Vapor Deposition, by TimeDomain CVD, Inc.