Retention Improvement of HZO-Based Ferroelectric Capacitors with TiO₂ Insets

Abstract

The influence of the bottom TiO 2 interfacial layer grown by atomic layer deposition on the ferroelectric properties of the TiN/ Hf 0.5 Zr 0.5 O 2 /TiN capacitors is systematically investigated. We show that the integration of the TiO 2 layer leads to an increase in the polar orthorhombic phase content in the Hf 0.5 Zr 0.5 O 2 film. In addition, the crystalline structure of the Hf 0.5 Zr 0.5 O 2 film is highly dependent on the thickness of the TiO 2 inset, with monoclinic phase stabilization after the increase of TiO 2 thickness. Special attention in this work is given to the key reliability parameters�retention and endurance. We demonstrate that the integration of the TiO 2 inset induces valuable retention improvement. Using a novel approach to the depolarization measurements, we show that the depolarization contribution to the retention loss is insignificant, which leaves the imprint effect as the root of the retention loss in TiN/TiO 2 /Hf 0.5 Zr 0.5 O 2 /TiN devices. We believe that the integration of the insulator interfacial layer suppresses the scavenging effect from the bottom TiN electrode, leading to a decrease in the oxygen vacancy content in the Hf 0.5 Zr 0.5 O 2 film, which is the main reason for imprint mitigation. At the same time, although the observed retention improvement is very promising for the upcoming technological integration, the field cycling testing revealed the endurance limitations linked to the phase transitions in the TiO 2 layer and the rise of the effective electric field applied to the Hf 0.5 Zr 0.5 O 2 film.

Interplay between Strain and Defects at the Interfaces of Ultra‐Thin Hf0.5Zr0.5O2‐Based Ferroelectric Capacitors

“…[ 58 ] In the case of sample TiN/HZO/W, STEM‐EELS data revealed the presence of an interfacial layer at TiN/HZO bottom interface, due to oxygen scavenging. [ 26,63,64 ] However, we concluded that both in‐plane strain from W TE and a thin dead‐layer at the HZO/W top interface were the key factors that notably improved the ferroelectric properties of samples TiN/HZO/W and W/HZO/W, where an extremely high value of switchable polarization was reached.…”

Enhanced Ferroelectricity in Hf‐Based Ferroelectric Device with ZrO2 Regulating Layer

“…[11] However, its low remnant polarization intensity and high annealing temperature have restricted its further development. [12] In order to improve the remanent polarization intensity of Hf-based ferroelectric materials, researchers generally insert an interface layer between the electrode and the ferroelectric layer, such as TiO 2 , [13,14] Al 2 O 3 , [15,16,17] HfO 2 , [18] ZrO 2 , [19,20] La 2 O 3 , [21] CeO x , [22] etc. Among them, there are reported works on the performance improvement of ZrO 2 layer in memory [23][24][25] and ZrO 2 has good lattice matching effect with HfO 2 , which was suitable as insert layer for improving performances of Hf-based devices.…”

Ferroelectric Enhancement in a TiN/Hf1–xZrxO2/W Device with Controlled Oxidation of the Bottom Electrode

“…The peak observed at 30.5° corresponds to the FE O -phase and T -phase denoted as (111) o /(101) t in the HZO material. This peak is an important indicator of the structural composition of the HZO, indicating the coexistence of FE O -phase, referred to as (111) o , and non-FE T -phase, referred to as (101) t . , The observed downward shift in the 2θ angle indicates the presence of tensile strain in the O -phase of the HZO thin film, which is conducive to the formation of the O -phase. Note that an upward peak shift would indicate the presence of compressive strain .…”