Robust low-temperature (350 °C) ferroelectric Hf0.5Zr0.5O2 fabricated using anhydrous H2O2 as the ALD oxidant

Abstract

In this Letter, the robust ferroelectric properties of low-temperature (350 °C) Hf0.5Zr0.5O2 (HZO) films are investigated. We demonstrate that the lower crystallization temperature of HZO films originates from a densified film deposition with an anhydrous H2O2 oxidant in the atomic layer deposition process. As a consequence of this densification, H2O2-based HZO films showed completely crystallinity with fewer defects at a lower annealing temperature of 350 °C. This reduction in the crystallization temperature additionally suppresses the oxidation of TiN electrodes, thereby improving device reliability. The low-temperature crystallization process produces an H2O2-based HZO capacitor with a high remanent polarization ( Pr), reduced leakage current, high breakdown voltage, and better endurance. Furthermore, while an O3-based HZO capacitor requires wake-up cycling to achieve stable Pr, the H2O2-based HZO capacitor demonstrates a significantly reduced wake-up nature. Anhydrous H2O2 oxidant enables the fabrication of a more reliable ferroelectric HZO device using a low process thermal budget (350 °C).

Toward Low-Thermal-Budget Hafnia-Based Ferroelectrics via Atomic Layer Deposition

“…(a) Effect of dopants on ferroelectricity of HfO 2 -based film. 25,29,37,38,[41][42][43][44][45][46][47][48]53,[57][58][59]61,63,69 (b) Effect of precursor selection in HZO films ferroelectricity. 25,29,38,49−64,66−69 (c) Oxygen source effect on the ferroelectric temperature of HZO films.…”

“…As reported in the literature, common oxidants used to deposit ferroelectric HZO include water (H 2 O), 49−54,56,58,66−68 ozone (O 3 ), 25,55,64,69 hydrogen peroxide (H 2 O 2 ), 29 and oxygen (O 2 ) plasma. 57,58 Unlike other molecular oxygen sources, O 2 plasma consists of highly reactive oxygen radicals and ions, providing extra energy during reactions.…”

“…As reported in the literature, common oxidants used to deposit ferroelectric HZO include water (H 2 O), − ,,,− ozone (O 3 ), ,,, hydrogen peroxide (H 2 O 2 ), and oxygen (O 2 ) plasma. , Unlike other molecular oxygen sources, O 2 plasma consists of highly reactive oxygen radicals and ions, providing extra energy during reactions. ,,, The additional energy supplied during the plasma cycle reduces the process temperature for ALD reaction and enhances the crystallization of plasma-enhanced ALD (PEALD) compared to TALD. , However, unlike TALD, the anisotropic nature of the plasma source is difficult to implement in complicated 3D structures and can produce a thick interfacial layer due to excessively strong oxidation power. ,, Consequently, the use of TALD is preferable to deposit a thin film on complex 3D structures conformally and minimize interface formation. Therefore, this section focuses on oxygen sources that are mainly used in TALD processes.…”

“…Therefore, selecting an oxygen source that produces HZO films with low hydrogen content and high density using ALD is one of the most crucial aspects of achieving superior electrical properties. Very few studies with HfO 2 and HZO ALD have shown that H 2 O 2 produces dense, highly stoichiometric films that are ideal for low-temperature applications. , H 2 O 2 has comparable oxidation power to O 3 and lower dissociation energy on O–O bonds (2.22 eV) than the O–O bond (3.77 eV) of O 3 , allowing it to react readily with the precursors. , In addition, H 2 O 2 is readily available in large quantities as a liquid that can be incorporated into the ALD system without any safety concerns. In this regard, Choi et al reported the ALD and HfO 2 film characteristics of 50 wt % H 2 O 2 as an oxygen source reacting with TEMA-Hf versus H 2 O .…”

“…2 and HZO ALD have shown that H 2 O 2 produces dense, highly stoichiometric films that are ideal for low-temperature 29,86. H 2 O 2 has comparable oxidation power to O 3 and lower dissociation energy on O−O bonds (2.22 eV) than the O−O bond (3.77 eV) of O 3 , allowing it to react readily with the precursors.…”