The deposition chambers for standard vacuum requirements 10^-5-10^-6 Torr use glass or stainless steel chambers. They are usually diffusion pumped. The CVD , thermal evaporation, sputter deposition films have typically polycrystalline quality. For ultrahigh vacuum (10^-8-10^-11 Torr) chamber requirements bakeable stainless steel is used. They are usually ion and/or turbo pumped. The thermal evaporated and sputter deposited films have epitaxial (better) quality films.

Physical Vapor Deposition

As discussed previously, Physical vapor deposition ( PVD ) is a technique used to deposit thin films of various materials onto of semiconductor wafers by physical means, as compared to chemical vapor deposition. Evaporation, Sputter Deposition and Pulsed laser deposition are examples of this method.

An evaporator uses a thermal or e-beam heating to melt the material and raise its vapor pressure to a useful range as shown in Fig. 3.21. This is done in a high vacuum, both to allow the vapor to reach the substrate without reacting with or scattering against other gas-phase atoms in the chamber. Only materials with a much higher vapor pressure than the heating element can be deposited without contamination of the film.