Influence of film thickness on the dielectric characteristics of hafnium oxide layers

Highlights: • Amorphous hafnium oxide films were deposited by reactive magnetron sputtering. • The deposited films are characterized by high uniformity and low surface roughness. • With a decrease of the film thickness, its dielectric characteristics drop. • This is due to a violation of the ionic polarization at the film interface. -- Abstract: The present work focuses on the study of properties of hafnium oxide (HfO₂) films, deposited by reactive magnetron sputtering of the Hf target in Ar/O₂ gas mixture. The X-ray diffraction analysis of the deposited films proved the amorphous structure of the films, which was also confirmed by the Raman spectroscopy. It was determined that as the HfO₂ film thickness had been decreased from 98.6 nm to 13.5 nm, film density had dropped from 9.52 to 9.26 g/cm². At the same time, the dielectric constant dropped from 21.3 to 8.0 units, and the dielectric loss tangent rose, especially at high frequencies. At the same time, the decrease in film thickness resulted in increased leakage currents at low electric field density E, and decreased leakage currents at high E. Improvement of dielectric characteristics and increase in leakage current with film thickness growth is a consequence of film densification and the formation of a crystalline phase. Thickness dependence of the dielectric constant is associated with the violation of the ionic polarization mechanism at the film electrode interface.