Spin Coating involves the acceleration of a liquid puddle on a rotating substrate. The coating material is deposited in the center of the substrate either manually or by a robotic arm. The physics behind spin coating involve a balance between centrifugal forces controlled by spin speed and viscous forces which are determined by solvent viscosity.
The spin coating technique consists of four basic stages:
Some variable process parameters involved in spin coating are:
The film-forming process is primarily driven by two independent parameters – viscosity and spin speed. The range of film thicknesses easily achieved by spin coating is 1-200mm. For thicker films, hi gh material viscosity, low spin speed, and a short spin time are needed. However, these parameters can affect the uniformity of the coat. Multiple coatings are preferred for a film thickness greater than 15mm .
The film thickness equations can be affected by the formation of a "skin" layer during the coating process. Skin layer formation is caused by the difference in the properties of the spinning material near the air interface and the properties of the bul k fluid.