Optical, electrical and mechanical properties of nitrogen-rich carbon nitride films deposited by inductively coupled plasma chemical vapor deposition

Abstract

An inductively coupled plasma utilizing chemical transport reactions has been used to deposit thin carbon nitride films with a high nitrogen content [N/(C+N) of approximately 0.5 or higher]. We report on the characterization of the application relevant properties of these films, especially the optical (refractive index, transmission), electrical (dielectric constant, resistivity) and mechanical characteristics (stress, hardness, wear resistance). The refractive index is in the order of 1.5–1.8 depending on the deposition conditions; furthermore, the films are highly transmitting for wavelengths above 600 nm. C– V curves indicate the insulating character of the CN x films which was confirmed by I– V measurements yielding resistivities up to 10 11 Ω cm at room temperature. The layers possess marginal stress as measured by the bending method on silicon cantilevers. The hardness is in the range of 1 GPa, and a friction coefficient of 0.6 was determined by ball-on-disc tests against stainless steel balls. The investigations showed that these films may be suited especially for optical and electrical applications. Finally, we correlate the films characteristics with the composition and structure of the coatings.