Chemical vapour deposition (CVD) is a technique in which gaseous reactants are deposited onto a substrate in order to create high-purity solid materials. The name encompasses a group of processes that involve depositing a solid material from a gaseous phase into a wafer or substrate.

Typically, CVD is used in the process of producing thin films for semiconductors. It starts when the wafer or substrate is exposed to one or more volatile precursor gases (often diluted in carrier gases) when delivered into the reaction chamber at ambient temperature. When these gasses come into contact with a heated substrate, they react and/or decompose on the substrate surface, forming a solid phase which is then deposited onto the wafer or substrate. Gas flow then removes all byproducts through the reaction chamber.

Chemical vapour deposition is done through vacuums, consisting of an internal reactor, collecting surface, gas delivery system, energy source, substrate loading mechanism, exhaust system, process control equipment, and of course the substrate.

The precursor gasses flow through the gas delivery system into the reactor chamber, where the reaction takes place. Heat is then provided by the energy source, with the process control equipment carefully monitoring the parameters. The vacuum system and exhaust system remove gaseous species and volatile byproducts from the chamber in order to allow the reaction to go on unhindered.

Coatings produced by CVD are usually fine grained, harder than other similarly conceived materials, impervious and have a high-purity. These coatings tend to be only a few microns thick and are deposited at the rate of a few microns per hour.

Chemical vapour deposition has many advantages as a method of deposition:

1. Can be performed with any element or compound
2. High Purity (99.999%)
3. High Density (100%)
4. The materials form below their melting point
5. Conformal and net shape
6. Many parts can be coated at the same time, making it economical

Because of its versatility, chemical vapour deposition can be used in a wide array of fields. Primarily, it is used in the production of semiconductors, but it is also used for coatings, optical fibers, composites, catalysts, nanomachines and powder production. It is also great in producing dense structural parts, as it has the ability to produce components that are difficult for conventional techniques to make.