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 N2 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.