Atomic Layer Deposition of La:Hf0.5Zr0.5O2 Thin Films with Abnormally High Dielectric Permittivity for Memory and Logic Devices

Abstract Ultrathin (~10 nm) functional layers of a high-k dielectric, Hf0.5Zr0.5O2 (HZO), precision-doped with lanthanum, were prepared by molecular layering (atomic layer deposition), and capacitor structures based on them were formed. Such doping suppresses the formation of the equilibrium monoclinic phase in HZO and leads to the formation of metastable tetragonal/orthorhombic phases. Electrophysical measurements demonstrate signs of the formation of a morphotropic boundary between these phases and abnormally high, for dielectrics based on HfO2/ZrO2, relative dielectric permittivity (k ~ 58). This quantity consists of the structure post-treatment conditions, namely, on the rapid thermal anneal (RTA) temperature. The maximal dielectric permittivity is reached at the RTA temperature of 550°С, with low leakage currents, <10–7 A cm–2, being preserved. Owing to such combination of properties, the functional layers synthesized show promise as high-k dielectrics in logic device transistors and in random-access memory cells.