Observation and characterization of defects in HfO2 high-K gate dielectric layers

A deeper understanding of Hf-based high-K materials in terms of their structural and electrical defects is important for device implementation. We have studied the occurrence of such defects using wet-etch defect delineation, electron microscopy, depth-profiling and conventional electrical measurements. It is evident that defects are present in HfO2 films that are related to the microstructure and stoichiometry of the film, which in turn depend on the deposition temperature, starting surface and post-deposition treatments. These results appear to be independent of the deposition technique. Two types of defects were observed, those that are physically visible and cause immediate failures especially on large-area structures, and those that cause high leakage but not immediate failures. The existence of defects affects not only leakage or performance but will also affect the reliability through trapping of charge at the defect sites. As films continue to be scaled thinner, the requirements on defect reduction to minimize electrical impact may become more stringent.