Crystallization kinetics and microstructure-dependent leakage current behavior of ultrathin HfO_(2) dielectrics: In situ annealing studies

摘要

The crystallization kinetics of ～3 nm HfO_(2) films grown by atomic layer deposition (ALD) on SiO_(2)-passivated Si (100) wafers were investigated using an in situ transmission electron microscope (TEM) with heating capability. Through gray-scale analysis of dark-field TEM images, it was found that a two-dimensional nucleation and growth mechanism with a decreasing of nucleation rate could account for the observed transformation rate behavior. The effects of crystalline defects (e.g., grain boundaries) on the leakage current were studied using a reduced pressure in situ postdeposition anneal in the ALD system to avoid interfacial SiO_(2) growth. The leakage current magnitude and temperature dependence were found to be essentially independent of the microstructural changes that accompany crystallization of the HfO_(2) films.