a process for forming dielectric thin film coating suitable for use in magnetic thin film heads includes the application of a spin - on - glass material on a substrate , the spinning of the substrate , the preheating of the substrate and thin film to remove the solvents in the spin - on - glass material , and the heating in a reducing or in an inert atmosphere of the film to provide a conversion to a sio 2 film . the reducing and the inert atmospheres permit carbon to be left in the film . the presence of the carbon improves structural properties of the thin films .