In the process of silicon wafer productions, at certain points in the assembly a liquid coating will be applied to the wafer. Since the coating applied will make up the photoresist of the wafer, the layer must have a uniform protective coating.
Wetting method is the procedure of coating an entire surface with a liquid. For silicon wafers, a spin coating is the wetting method used to apply a liquid layer.
The process begins with the wafer being placed on the spin coater, a machine that spins an object in a circular motion to use centrifugal force to spread a liquid coating uniformly across the surface of the material. Two liquids will generally be used during the process, an adhesion promoter and the photoresist itself. First, the adhesion promoter will be placed on the wafer and then spun, and then the photoresist is placed on the wafer, spun again to spread the layer out evenly.
For the desired finish, one may alter the concentration of the solutions used, spin duration, and the revolutions per minute the wafer spins.
The wetting method allows for a business to uniformly apply coatings to a surface, saving money, materials, and man power for a mass manufacturing process.