Dysprosium Incorporation for Phase Stabilization of Atomic-Layer-Deposited HfO₂ Thin Films

The relatively low thermal stability of HfO₂ films severely affects the performance of semiconductor devices. For instance, the low crystallization temperature of HfO₂ (∼500 °C) leads to the formation of grain boundaries, which increases the leakage current. In this study, Dy incorporation leads to the phase transformation of HfO₂ films from various directional planes to a main m(−111) plane by the crystallographic stabilization of HfO₂ films, increasing the size of grains. Dy-doped HfO₂ thin films with modulated doping content, prepared by plasma-enhanced atomic layer deposition (PE-ALD), are characterized by analysis of their chemical composition combined with electron microscopy and synchrotron X-ray techniques. The transformation from m(110), m(−111), m(111), m(020), and m(120) to a main m(−111) plane is observed through X-ray diffraction, which indicates that Dy plays a role for the phase stabilization of HfO₂ films. The atomic-scale images of the cross section and top view obtained using an electron microscope demonstrate that the in-plane average grain size is increased by approximately 4 times due to Dy incorporation compared with that of single HfO₂ films. The reduction in the area of the grain boundary of HfO₂ due to Dy incorporation decreases the leakage current density of HfO₂ by 1000 times and increased the breakdown strength. This result can aid future electronics by determining the effect of a dopant on the crystallographic structure of host thin-film materials.