Photoinduced Leakage Currents in Silicon Carbon Nitride Dielectrics for Copper Diffusion Barriers

The current conduction in silicon carbon nitride (SiCN) dielectric films subjected to ultraviolet (UV) illumination at room temperature has been investigated. After exposure of SiCN single-layer and SiCN–SiO₂ double-layer films to 4.9-eV UV illumination, leakage currents through both films substantially increased under positive and negative gate biases. The current increased as a function of the change in paramagnetic defect density, which was obtained from electron spin resonance signals of the SiCN and SiCN–SiO₂ films subjected to 4.9-eV UV illumination. We suggest that the paramagnetic defects, which have been identified as neutrally charged silicon dangling bonds, act as generation centers and that their formation is responsible for the current increase. The conduction mechanisms of the photoinduced leakage current are discussed in detail.