Chemical Vapor Deposition
Definition and meaning of Chemical Vapor Deposition in chemistry.
Chemical vapor deposition (CVD) is a materials-synthesis process in which volatile precursor gases react or decompose at or near a heated substrate surface, depositing a solid thin film while volatile byproducts are carried away in the gas stream.
In more detail
The substrate is placed in a reactor and heated (or exposed to a plasma) so that gas-phase precursor molecules adsorb, decompose, and react on the surface, building the film atom layer by atom layer through surface chemical reactions rather than simple condensation. Reactor pressure, temperature, and gas flow rates control film composition, crystallinity, thickness uniformity, and growth rate. CVD is central to semiconductor fabrication, producing silicon epitaxial layers, silicon dioxide and silicon nitride dielectrics, tungsten interconnects, and synthetic diamond coatings. Common variants include low-pressure CVD (LPCVD), plasma-enhanced CVD (PECVD), and metal-organic CVD (MOCVD), each tuned to lower deposition temperature or improve step coverage.
Key facts
| Field | Inorganic Chemistry |
|---|---|
| Typical temperature range | 200-1600 °C, process-dependent |
| Common precursors | SiH4, WF6, TiCl4, metal-organic complexes |
| Contrast | Physical vapor deposition (PVD) uses no chemical reaction at the substrate |
In microelectronics, polycrystalline or epitaxial silicon films are grown by flowing silane over a silicon wafer heated to about 600-650°C: SiH4(g) → Si(s) + 2 H2(g). The hydrogen byproduct desorbs and is swept away, leaving a uniform silicon film on the substrate.
Frequently asked questions
How does CVD differ from physical vapor deposition (PVD)?
CVD builds a film through chemical reactions of gaseous precursors on the substrate surface, whereas PVD (e.g., sputtering or thermal evaporation) transfers material physically from a solid source to the substrate without a surface chemical reaction.
What is plasma-enhanced CVD (PECVD) used for?
PECVD uses a plasma to supply energy for precursor decomposition, allowing film deposition at much lower substrate temperatures than thermal CVD, which is essential for coating temperature-sensitive materials like polymers or finished device layers.