Thin films of SiN(x) were prepared from mixtures of SiH4/Ar and N2 employing a compact 2.45 GHz electron cyclotron resonance plasma source. The composition of these layers as a function of gas flows, extraction magnetic field and substrate bias was studied. Growth rates of 3 - 4 nm min-1 are typical. The refractive index can be varied from 1.92 to 3.6, depending on experimental conditions. Computer control was implemented to achieve controlled growth of graded refractive index profiles suitable for application in rugate optical interference filters. Rugate filters were grown by the electron cyclotron plasma deposition technique for the first time. Optical reflectance measurements in the 3800-13 000 cm-1 range were used to evaluate characteristics of the rugate filters.