Silicon nitride thin films deposited at room temperature by the method of reactive ion beam sputtering have been investigated. Silicon target was used for the film preparation with nitrogen ion beam generated in the magnetic multipole plasma source (bucket ion source). As increasing ion current, the deposition rate of the film became higher. However, we found no effects on the film composition or the optical characteristics. We used this silicon nitride thin film for the protective and the dielectric layer of magneto optical disk and the carrier to noise ratio of 48 dB was obtained.
