Editing Chemical vapor deposition (section)

== Types ==
[[File:ThermalCVD-en.svg|thumb|Hot-wall thermal CVD (batch operation type)]]
[[File:PlasmaCVD-en.svg|thumb|Plasma assisted CVD]]

CVD is practiced in a variety of formats. These processes generally differ in the means by which chemical reactions are initiated.
* Classified by operating conditions:
** Atmospheric pressure CVD (APCVD) – CVD at atmospheric pressure.
** Low-pressure CVD (LPCVD) – CVD at sub-atmospheric pressures.<ref>{{cite web|url=http://www.crystec.com/klllpcvde.htm|title=Low Pressure Chemical Vapor Deposition – Technology and Equipment|publisher=Crystec Technology Trading GmbH}}</ref> Many journal articles and commercial tools use the term reduced pressure CVD (RPCVD)<ref>{{cite journal|last1=Shah|first1=V.A.|last2=Dobbie|first2=A.|last3=Myronov|first3=M.|last4=Leadley|first4=D.R.|title=Reverse graded SiGe/Ge/Si buffers for high-composition virtual substrates|journal=Journal of Applied Physics|volume=107|number=6|pages=064304–064304–11|year=2010|url=https://pubs.aip.org/aip/jap/article-pdf/doi/10.1063/1.3311556/13203363/064304\_1\_online.pdf|doi=10.1063/1.3311556|bibcode=2010JAP...107f4304S |issn=0021-8979}}</ref> especially for single wafer tools in place of LPCVD which dominates for multi-wafer furnace tube tools. Reduced pressures tend to reduce unwanted gas-phase reactions and improve film uniformity across the wafer.
** Ultrahigh vacuum CVD (UHVCVD) – CVD at very low pressure, typically below 10<sup>−6</sup> [[Pascal (unit)|Pa]] (≈&nbsp;10<sup>−8</sup> [[torr]]). Note that in other fields, a lower division between high and [[ultra-high vacuum]] is common, often 10<sup>−7</sup> Pa.
** Sub-atmospheric CVD (SACVD) – CVD at sub-atmospheric pressures. Uses [[tetraethyl orthosilicate]] (TEOS) and [[ozone]] to fill high aspect ratio Si structures with silicon dioxide (SiO<sub>2</sub>).<ref>{{Cite journal|last1=Shareef|first1=I. A.|last2=Rubloff|first2=G. W.|last3=Anderle|first3=M.|last4=Gill|first4=W. N.|last5=Cotte|first5=J.|last6=Kim|first6=D. H.|date=1995-07-01|title=Subatmospheric chemical vapor deposition ozone/TEOS process for SiO<sub>2</sub> trench filling|journal=Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena|volume=13|issue=4|pages=1888–1892|doi=10.1116/1.587830|bibcode=1995JVSTB..13.1888S|issn=1071-1023}}</ref>

Most modern CVD is either LPCVD or UHVCVD.
* Classified by physical characteristics of vapor:
** Aerosol assisted CVD (AACVD) – CVD 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 non-volatile precursors.
** Direct liquid injection CVD (DLICVD) – CVD 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). The precursor vapors are then transported to the substrate as in classical CVD. This technique is suitable for use on liquid or solid precursors. High growth rates can be reached using this technique.
* Classified by type of substrate heating:
** Hot wall CVD – CVD in which the chamber is heated by an external power source and the substrate is heated by radiation from the heated chamber walls.
** Cold wall CVD – CVD in which only the substrate is directly heated either by induction or by passing current through the substrate itself or a heater in contact with the substrate. The chamber walls are at room temperature.
* Plasma methods (see also [[Plasma processing]]):
** Microwave plasma-assisted CVD (MPCVD)
** [[Plasma-enhanced chemical vapor deposition|Plasma-enhanced CVD]] (PECVD) – CVD that utilizes [[Plasma (physics)|plasma]] to enhance chemical reaction rates of the precursors.<ref>{{citation|url=http://www.crystec.com/tridepe.htm|title=Crystec Technology Trading GmbH, Plasma Enhanced Chemical Vapor Deposition – Technology and Equipment}}</ref> PECVD processing allows deposition at lower temperatures, which is often critical in the manufacture of semiconductors. The lower temperatures also allow for the deposition of organic coatings, such as plasma polymers, that have been used for [[nanoparticle]] surface functionalization.<ref>{{cite journal|last=Tavares|first=Jason|author2=Swanson, E.J. |author3=Coulombe, S. |title=Plasma Synthesis of Coated Metal Nanoparticles with Surface Properties Tailored for Dispersion|journal=Plasma Processes and Polymers|year=2008|volume=5|issue=8|page=759|doi=10.1002/ppap.200800074}}</ref>
** 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.
** [[LEPECVD|Low-energy plasma-enhanced chemical vapor deposition]] (LEPECVD) - CVD employing a high density, low energy plasma to obtain epitaxial deposition of semiconductor materials at high rates and low temperatures.
* Atomic-layer CVD ([[ALCVD]]) – Deposits successive layers of different substances to produce layered, [[crystal]]line films. See [[Atomic layer epitaxy]].
* [[Combustion chemical vapor deposition]] (CCVD) – Combustion Chemical Vapor Deposition or flame pyrolysis is an open-atmosphere, flame-based technique for depositing high-quality thin films and [[nanomaterials]].
* Hot filament CVD (HFCVD) – also known as catalytic CVD (Cat-CVD) or more commonly, initiated CVD, this process uses a hot filament to chemically decompose the source gases.<ref>{{cite conference | first=R.E.I. | last=Schropp |author2=B. Stannowski |author3=A.M. Brockhoff |author4=P.A.T.T. van Veenendaal |author5=J.K. Rath | title=Hot wire CVD of heterogeneous and polycrystalline silicon semiconducting thin films for application in thin film transistors and solar cells | book-title=Materials Physics and Mechanics | pages=73–82 | url=http://www.ipme.ru/e-journals/MPM/no_2100/schropp/schropp.pdf |archive-url=https://web.archive.org/web/20050215180245/http://www.ipme.ru/e-journals/MPM/no_2100/schropp/schropp.pdf |archive-date=2005-02-15 |url-status=live }}</ref> The filament temperature and substrate temperature thus are independently controlled, allowing colder temperatures for better absorption rates at the substrate and higher temperatures necessary for decomposition of precursors to free radicals at the filament.<ref>{{cite journal|last=Gleason|first=Karen K.|author2=Kenneth K.S. Lau |author3=Jeffrey A. Caulfield |s2cid=96618488|title=Structure and Morphology of Fluorocarbon Films Grown by Hot Filament Chemical Vapor Deposition|journal=Chemistry of Materials|date=2000|volume=12|issue=10|page=3032|doi=10.1021/cm000499w}}</ref>
* [[Hybrid physical–chemical vapor deposition|Hybrid physical-chemical vapor deposition]] (HPCVD) – This process involves both chemical decomposition of precursor gas and [[vaporization]] of a solid source.
* [[Metalorganic chemical vapor deposition]] (MOCVD) – This CVD process is based on [[metalorganic]] precursors.
* Rapid thermal CVD (RTCVD) – This CVD process uses 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 (ecology)|particle]] formation.
* Vapor-phase epitaxy (VPE)
* Photo-initiated CVD (PICVD) – This process uses UV light to stimulate chemical reactions. It is similar to plasma processing, given that plasmas are strong emitters of UV radiation. Under certain conditions, PICVD can be operated at or near atmospheric pressure.<ref>{{cite journal|last=Dorval Dion|first=C.A.|author2=Tavares, J.R.|title=Photo-Initiated Chemical Vapour Deposition as a Scalable Particle Functionalization Technology (A Practical Review)|journal=Powder Technology|volume=239|pages=484–491|year=2013|doi=10.1016/j.powtec.2013.02.024|url=https://publications.polymtl.ca/2773/1/2013_Dorval_Dion_Photo-initiated_chemical_vapor_deposition_scalable.pdf|url-access=|url-status=|archive-url=|archive-date=}}</ref>
* [[Laser chemical vapor deposition]] (LCVD) - This CVD process uses lasers to heat spots or lines on a substrate in semiconductor applications. In MEMS and in fiber production the lasers are used rapidly to break down the precursor gas—process temperature can exceed 2000&nbsp;°C—to build up a solid structure in much the same way as laser sintering based 3-D printers build up solids from powders.