Correlation between defects, leakage currents and conduction mechanisms in thin high-k dielectric layers

Results on leakage currents and conduction mechanisms in various high-k dielectric layers (Zr-, Hf-, HfTi-silicates and Ta2O5) are presented. It is demonstrated that small alteration of the dielectric composition results in significant difference in the leakage current level, polarity dependence and change in the dominating conduction mechanism. These differences are commented in terms of both band diagrams and defects in the dielectric films. A special attention is given to the influence of the defect nature, their density and spatial and energy location on the dominating conduction mechanism. Examples of defect parameters influencing the charge trapping in the high-k stacks are given. Qualitative models explaining the conduction properties of the structures are presented.