Spin coating

Laurell Technologies WS-400 spin coater used to apply photoresist to the surface of a silicon wafer.

Spin coating is a procedure used to deposit uniform thin films to flat substrates. Usually a small amount of coating material is applied on the center of the substrate, which is either spinning at low speed or not spinning at all. The substrate is then rotated at high speed in order to spread the coating material by centrifugal force. A machine used for spin coating is called a spin coater, or simply spinner.

Rotation is continued while the fluid spins off the edges of the substrate, until the desired thickness of the film is achieved. The applied solvent is usually volatile, and simultaneously evaporates. So, the higher the angular speed of spinning, the thinner the film. The thickness of the film also depends on the viscosity and concentration of the solution and the solvent. [1] A widely studied phenomenon in spin-coating is the coffee ring effect.

Spin coating is widely used in microfabrication of functional oxide layers on glass or single crystal substrates using sol-gel precursors, where it can be used to create uniform thin films with nanoscale thicknesses. [2] It is used intensively in photolithography, to deposit layers of photoresist about 1 micrometre thick. Photoresist is typically spun at 20 to 80 revolutions per second for 30 to 60 seconds.

References

  1. ↑ Scriven, LE (1988). "Physics and applications of dip coating and spin coating". MRS proceedings. 121.
  2. ↑ Hanaor, DAH; Triani, G; Sorrell, CC (2011). "Morphology and photocatalytic activity of highly oriented mixed phase titanium dioxide thin films". Surface and coatings technology. 205 (12): 3658–3664.
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