Exploring the role of TiN electrodes in the formation of ferroelectric HfxZr1-xO2 thin films through transmission electron microscopy

Abstract

The development of ferroelectric HfO2-based thin films, with their potential to revolutionize semiconductor technology, relies on comprehending the factors that drive the formation of the polar orthorhombic phase. Although TiN electrodes are known to facilitate orthorhombic phase formation, a comprehensive understanding is still lacking. Our study offers an in-depth exploration of the pivotal role played by TiN electrodes in shaping ferroelectric (Hf,Zr)O-2-based thin films using transmission electron microscopy (TEM). Through direct depositions of Hf0.65Zr0.35O2 (HZO) thin films and TiN masks onto a silicon membrane TEM grid, we enable a straightforward structural comparison between HZO thin films annealed with and without a TiN capping layer. This approach ensures uniform conditions across all parameters, except the presence of the TiN capping layer, while eliminating potential artifacts introduced during the TEM sampling. Our comprehensive analysis, incorporating electron diffraction, high-resolution TEM (HR-TEM), and electron energy loss spectroscopy (EELS), delves into the possible influences of factors such as tensile strain, oxygen vacancies, and the surface atomic mobility constraint effect induced by the TiN capping layer. The results underscore the dominant role of TiN in surface atomic mobility constraint, thereby significantly contributing to the formation of ferroelectric HZO. This research promises to advance our understanding of ferroelectric materials, thus expediting the progress of ferroelectric and semiconductor technology.