Spin coating
The spin coating (engl. Spin coating and spin-on ) a method of coating is thinner and more uniform layers or films on a substrate . All materials in solution, such as the photoresist used in microelectronics , are suitable for spin coating .
Process flow
The substrate, often a wafer , is fixed on a turntable, the chuck , on the underside by means of vacuum suction. The desired amount of the solution is applied with a metering device over the center of the wafer. Acceleration , final speed and time are set on the spin coater and the solution is evenly distributed over the wafer surface. Any excess material is spun off the wafer. Typically polymer solutions are used, whereby the molar mass and its distribution also have a direct influence on the film thickness (see details, models and useful equations).
In order to obtain a solid layer, it is necessary to remove the solvent. Part of the solvent evaporates when it is spun on. This can be increased by a heated chuck or by subsequent heating ( tempering , soft bake ).
use
The process is used for coating wafers in microelectronics and microsystem technology . The resulting layer thickness on the wafer depends on the viscosity of the photoresist, the speed of rotation , the acceleration and the process duration of the spin coating.
In microelectronics, layer thicknesses of one micrometer and less are common, since the photoresist ( resist ) only serves as a cover layer. The structures are later etched directly into the wafer. Higher structures are also required in microsystem technology. In this area, layer thicknesses down to the millimeter range are built up in one or more process steps, since the structures to be produced are often made using the photoresist, e.g. B. by electroplating processes .
Spin coating is moreover used in biology, in order to substrates for cell culture or microscopy, such as slides or coverslips , the cell adhesion to increase. A typical coating is poly- D - lysine .
Individual evidence
- ↑ Dirk W. Schubert, Thomas Dunkel: Spin coating from a molecular point of view: its concentration regimes, influence of molar mass and distribution. In: Materials Research Innovations 7, 2003, pp. 314-321 ( doi : 10.1007 / s10019-003-0270-2 ).
literature
- K. Norrman, A. Ghanbari-Siahkali, NB Larsen: Studies of spin-coated polymer films . In: Annual Reports Section C (Physical Chemistry) . tape 101 , 2005, pp. 174–201 , doi : 10.1039 / b408857n (freely accessible).
Web links
- Spin coating process. (PDF, 219 KB) Columbia University Center for Integrated Science and Engineering, p. 6 , accessed on March 15, 2014 .