Process and apparatus for interior coating of strongly curved, essentially dome-shaped substrates by CVD

In the process, the reaction gases, which contain the film-forming molecules, are passed into the reaction chamber containing the substrate(s) to be coated through at least one gas inlet opening situated opposite the apex of the dome at a distance from the surface to be coated. The coating material is then deposited on the substrate in a manner known per se by creating a reaction zone at the substrate interior surface to be coated. According to the invention, the reaction gases are not allowed to flow slowly into the reaction chamber as in known processes, but, in order to produce a uniform coating, they are fed into the reaction chamber at such a high velocity that the condition: 400 < R x h [mm] < 4000 is valid for the product of the Reynolds number R of the gas jet in the gas inlet opening or in its immediate vicinity and the distance h between the gas inlet opening and the apex of the dome. The method according to the invention has the advantage that it is possible to dispense with measures, otherwise necessary, for creating a laminar reaction-gas flow and measures for the spatial limitation of the reaction zone to avoid glass soot formation without impairing the layer quality. The gas jet can be created by means of simple nozzle bodies which can be used universally, even in the case of mutually differing substrate geometries.