Spin coating

Spin-coating ( spin coating Sheet also spin-on ) is a method for applying thin and uniform layers or films on a substrate. For spin are all present in solution materials such as photoresist used in microelectronics.

Process flow

The substrate is often a wafer, the chuck is fixed on a rotary table, by means of vacuum suction at the bottom. With a metering device above the center of the wafer the desired amount of solution is applied. Acceleration, the final rotational speed and time can be set on a spin- coater, and the solution is uniformly distributed over the wafer surface. Any excess material is spun off from the wafer. Typically, polymer solutions are used, the molar mass and its distribution has a direct influence on the film thickness have (for details, see Models and useful equations ).

To obtain a solid layer, it is necessary to remove the solvent. A portion of the solvent evaporates during spin already. This can be increased by a heated chuck or by subsequent annealing (annealing, soft bake).

Use

The process is used in the resist coating of wafers in the microelectronics and microsystems technology. The resulting layer thickness on the wafer is dependent on the viscosity of the resist, the rotation speed, acceleration and duration of the spin coating process.

In the microelectronics layer thicknesses of one micrometre and including common, since the photoresist (English: resist ) is used only as a cover layer. The structures are later etched directly into the wafer. In microsystems technology, higher structures are needed. In this area, layer thicknesses are built up to the millimeter range in one or more process steps, because the structures to be produced are often created by using the photoresist, eg, by electroplating method.