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Chemical vapor deposition

• http://en.wikipedia.org
 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 by-products are also produced, which are removed by gas flow through the reaction chamber.
 
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.
 

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 process at atmospheric pressure. Low-pressure CVD (LPCVD) – CVD process at sub-atmospheric pressures.[1] Reduced pressures tend to reduce unwanted gas-phase reactions and improve film uniformity across the wafer. Ultrahigh vacuum CVD (UHVCVD) – CVD process at very low pressure, typically below 10−6 Pa (~10−8 torr). Note that in other fields, a lower division between high and ultra-high vacuum is common, often 10−7 Pa.

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