Structural and electronic properties of HfO₂ films on Si through H₂O₂ wet oxidation with improved thermal stability

Abstract

The thermal stability and material properties of HfO2 thin films on Si substrates with and without H2O2 wet chemical oxidation were investigated. The HfO2 samples were deposited through plasma‐enhanced atomic layer deposition and subjected to thermal annealing. They were then examined using X‐ray diffraction, transmission electron microscopy, X‐ray photoelectron spectroscopy, reflection electron energy loss spectroscopy, and conductive atomic force microscopy. For the Si substrate without H2O2 wet chemical oxidation, a native oxide (~1.8 nm) was formed on the substrate before HfO2 deposition. After the annealing process at 600°C, the band gap (Eg) of the HfO2 films increased from 6.0 to 6.2 eV due to the diffusion of Si into HfO2. Furthermore, the conduction and valence band offsets (ΔEc and ΔEv, respectively) between HfO2 and Si changed from 1.02 to 1.42 and 3.86 to 3.66 eV, respectively. After the H2O2 wet oxidation of the Si substrate, a 1.5‐nm chemical oxide was formed instead of a native oxide. The band offset and Eg values of HfO2 were similar before and after 600°C annealing (ΔEv = 3.86 eV, ΔEc = 1.02 eV, and Eg = 6.0 eV), implying the high thermal stability of the HfO2 films. Accordingly, wet oxidation not only prevents diffusion from chemical oxide but also markedly improves the oxide leakage current, which is useful for developing highly efficient and thermally stable HfO2 gate oxides in Si‐based integrated circuit devices.

The Effects of Ag Nanoislands on the Volatile Threshold-Switching Behaviors of Au/Ag/HfO2/Ag Nanoislands/Au Devices

“…Figure 1(e) shows the GIXRD spectrum of Au/Ag(2 nm)/HfO 2 (4 nm)/Ag NIs/Au device. The hafnium oxide (JCPDS#34-0104) prepared by PEALD has one feature diffraction peak belonging to the (221) crystal plane [34,35], and strong feature diffraction peaks were not observed possibly due to the special crystal texture of the HfO 2 deposited.…”

The Excellent Bending Limit of a Flexible Si-Based Hf0.5Zr0.5O2 Ferroelectric Capacitor with an Al Buffer Layer

“…One of the primary challenges in manufacturing flexible Si-based ferroelectric devices is the necessity to thin the Si substrate to below 50 µm. Various methods, including wet or dry etching, have been proposed for thinning Si substrates, but they often introduce defects and regional stress concentrations, leading to cracks that grow over time and compromise the bending limit and ferroelectric properties [16,17]. To address these issues, Liu et al [18] employed a solution of 90% HF and 10% HNO 3 to reduce stress concentration and improve the bending limit by mitigating surface defects through strong acid etching.…”