MEMS deposition technologies are:

Depositions by chemical reaction:

Chemical Vapor Deposition (CVD)

Electrodeposition

Epitaxy

Thermal oxidation

Depositions by physical reaction:

Physical Vapor Deposition (PVD)

Casting

In the chemical process solid materials are made directly from chemical reactions in gas and/or liquid compositions or with the substrate material and the byproducts include gases, liquids and even other solids. In the physical process material deposited is physically moved on to the substrate as in the case of casting.

Here the substrate is placed inside a reactor to which a number of gases are supplied and the product is solid material which condenses on all surfaces inside the reactor. In MEMS Low Pressure CVD (LPCVD) and Plasma Enhanced CVD (PECVD) processes are used. The LPCVD process produces layers with excellent uniformity of thickness and material characteristics at a high deposition temperature (more than 600°C) at a slow rate. The PECVD process works at lower temperatures (down to 300° C) due to the extra energy supplied to the gas molecules by the plasma in the reactor, but the quality of the films is inferior and can deposit the material on one side of the wafers on 1 to 4 wafers at a time. LPCVD systems deposit films on both sides of at least 25 wafers at a time.