Metal films are generally deposited by evaporation or sputtering. The mechanical properties of metal film structures are not well understood, and differ greatly from bulk properties because of the complicated grain structure, as well as the presence of surface layers. Photoresist Photoresist is an organic material used in lithographic pattern transfer processes. At high temperatures, material begins to evaporate from the source, and travel by line of sight to the target. Coating is generally by line of sight, so textured surfaces are not coated uniformly.
High vacuum is required to prevent reaction of evaporated material during flight to target.
This process can coat both sides of as many as 200 wafers at a time. Uniformity is easily achieved. The energy associated with the plasma excitation stimulates the chemical reaction and enables it to occur at low temperature. This process can coat 1 side of 10 wafers at a time. Uniformity can be difficult to achieve.