Microstructures of HfOx Films Prepared via Atomic Layer Deposition Using La(NO3)3·6H2O Oxidants

Abstract

Hafnium oxide (HfOx) films have a wide range of applications in solid-state devices, including metal–oxide–semiconductor field-effect transistors (MOSFETs). The growth of HfOx films from the metal precursor tetrakis(ethylmethylamino) hafnium with La(NO3)3·6H2O solution (LNS) as an oxidant was investigated. The atomic layer deposition (ALD) conditions were optimized, and the chemical state, surface morphology, and microstructure of the prepared films were characterized. Furthermore, to better understand the effects of LNS on the deposition process, HfOx films deposited using a conventional oxidant (H2O) were also prepared. The ALD process using LNS was observed to be self-limiting, with an ALD temperature window of 200–350 °C and a growth rate of 1.6 Å per cycle, two times faster than that with H2O. HfOx films deposited using the LNS oxidant had smaller crystallites than those deposited using H2O, as well as more suboxides or defects because of the higher number of grain boundaries. In addition, there was a difference in the preferred orientations of the HfOx films deposited using LNS and H2O, and consequently, a difference in surface energy. Finally, a film growth model based on the surface energy difference was proposed to explain the observed growth rate and crystallite size trends.

Vertical Metal‐Oxide Electrochemical Memory for High‐Density Synaptic Array Based High‐Performance Neuromorphic Computing

“…Two characteristic peaks of Hf 4+ centered at 16.8 eV (Hf‐4 f 7/2 ) and 18.4 eV (Hf‐4 f 5/2 ) and two small sub‐oxidized peaks of Hf n + ( n < 4) centered at 16.0 eV (Hf‐4 f 7/2 ) and 17.6 eV (Hf‐4 f 5/2 ) can be observed. [ 26,27 ] Figure 2f also shows two peaks near O‐1 s centered at 530.1 and 531.5 eV, which corresponded to lattice oxygen in HfO 2 (O‐Hf) and oxygen vacancies, respectively. [ 28 ] The existence of oxygen vacancies in HfO 2 , which are intrinsic point defects, can facilitate the oxygen ion migration, leading to concentration modulation of the oxygen vacancies in the channel.…”