Schottky diodes are discussed as an alternative for pn junctions for application to Cu diffusion barrier tests. The Cu/TiN/p-Si system seems very promising for sensitive leakage current tests since Cu is shown to have a significantly lower barrier height to p-Si (0.55 + 0.01 eV as deposited) than TiN (0.90±0.01 eV after 300°C, 60 min). Furthermore the TiN/p-Si diodes maintain a high Schottky barrier even after annealing at 700°C (0.8±0.01 eV). An application of the proposed barrier test is given by an investigation of the thickness and N 2 flow dependence of reactively sputtered TiN diffusion barrier stability. While most samples show increased leakage currents after 450°C, the one with the 20 nm TiN barrier maintains its low leakage current up to 500°C annealing.