Electrode effects on the breakdown characteristics of high-k HfO2 metal-insulator-metal capacitors

The effects of top metal contacts on the leakage current and breakdown characteristics of HfO₂ metal-insulator-metal (MIM) capacitors were investigated. It is found that the breakdown field strength of the devices scales with the work function of the top electrode; the higher the metal work function the higher the breakdown field strength of the devices. This observation is attributed to the different barrier height formed at the contacting metal/HfO₂ interfaces, which results in various amount of charge injected into the HfO₂ dielectrics. The joule heating from these injected charges increases the defect density leading to dielectric breakdown.