vapor deposition

vapor deposition

Vapor deposition

Production of a film of material often on a heated surface and in a vacuum. Vapor deposition technology is used in a large variety of applications. Coatings are produced from a wide range of materials, including metals, alloys, compound, cermets, and composites. The vapor deposition processes can be classified into the two basic groups, physical (evaporation and sputtering) and chemical. In addition, there are hybrid processes such as ion plating, which is a subset of evaporation or sputter deposition. This process involves an electrically biased substrate and uses a working gas such as argon, which results in ion bombardment of the substrate/depositing film that produces changes in microstructure, residual stress, and impurity content. See Alloy, Cermet, Composite material, Metal

All deposition processes consist of three major steps: generation of the depositing species, transport of the species from source to substrate, and film growth on the substrate. In chemical vapor deposition, these steps occur simultaneously at or near the substrate. Physical vapor deposition processes are more versatile, because the steps occur sequentially and can be controlled independently.

In physical vapor deposition the first step involves generation of the depositing species by evaporation using resistance, induction, electron-beam, or laser-beam heating, or by sputtering using direct-current or radio-frequency plasma generation. The second step involves transport from source to substrate.

The third step is film growth on the substrate. The two basic processes for physical vapor deposition are evaporation deposition and sputter deposition. In evaporation, thermal energy converts a solid or liquid target material to the vapor phase. In sputtering, the target is biased to a negative potential and bombarded by positive ions of the working gas from the plasma, which knock out the target atoms and convert them to vapor by momentum transfer. See Sputtering

In the basic thermal chemical vapor deposition process, the reactants flow over a heated substrate and react at or near the substrate surface to deposit a film. The kinetics of the process are dependent on diffusion through the boundary layer between the substrate and the bulk gas-flow region.

Chemical vapor deposition is one of several process steps for fabrication of integrated circuits. Thus, much effort is being directed at lowering the deposition processing temperatures in order to achieve more economical processing as well as increasing the compatibility with preceding and subsequent steps in device processing. See Integrated circuits

Coatings provided by vapor deposition have many applications. For optical functions they are used as reflective or transmitting coatings for lenses, mirrors, and headlamps; for energy transmission and control they are used in glass, optical, or selective solar absorbers and in heat blankets; for electrical and magnetic functions they are used for resistors, conductors, capacitors, active solid-state devices, photovoltaic solar cells, and magnetic recording devices; for mechanical functions they are used for solid-state lubricants, tribological coatings for wear and erosion resistance in cutting and forming tools and other engineering surfaces; and for chemical functions they are used to provide resistance to chemical and galvanic corrosion in high-temperature oxidation, corrosion, and catalytic applications as well as to afford protection in the marine environment. Decorative applications include toys, costume jewelry, eyeglass frames, watchcases and bezels, and medallions. Vapor-deposited coatings also act as moisture barriers for paper and polymers. They can be used for bulk or free-standing shapes such as sheet or foil tubing, and they can be formulated into submicrometer powders. See Vacuum metallurgy