Various methods can be used for coating substrates with photosensitive resists or other materials. The substrate – usually a silicon wafer – is held by suction on a chuck during the process. The solution is then applied to the substrate surface. Wafer structure determines the choice of application techniques. Spin coating is the method most frequently used by far. This technique is applied with wafers having no or only very little surface structure. Spray coating is an alternative technique mainly used for wafers with a highly structured surface.
Spin coating is the process of evenly coating a spinning substrate with a solution. The solution, for instance a photosensitive resist, is dispensed at the center of the wafer. Subsequent acceleration as well as the rotation speed and the time allotted to the individual steps ensure that a homogeneous layer thickness remains after excess resist is spun off. Alongside the process parameters, the physical properties of the solution or photoresist determine the thickness of the applied film.
SUSS MicroTec’s patented GYRSET technology provides cutting-edge advantages. The GYRSET principle entails synchronous rotation of the process chamber during coating, in this way effectively reducing air turbulence over the rotating substrate. The atmosphere within the closed chamber becomes more quickly saturated with solvents, so that the resist dries more slowly and is thus distributed more evenly over the substrate. This results in significant savings in terms of required material.
Spin coating is limited in use to structures without high topography.
Features and Benefits
- Spin coating: a simple and widely used technique
- Patented GYRSET technique reduces the material required and cuts costs
Fully Automated Systems
Spray coating involves spray application of the solution to the wafer through a nozzle. The path traveled by the nozzle over the wafer is optimized to ensure that the coating is applied evenly to the substrate. The solutions used in spray coating usually feature a very low viscosity, which guarantees that fine droplets form.
Spray coating ensures a uniform layer even with high topography substrates, making it the preferred technique for structures of this kind. Even square substrates can be easily coated using the spray technique.
Features and Benefits
- Uniform coating even of highly structured surfaces