Paraelectric/antiferroelectric/ferroelectric phase transformation in As-deposited ZrO2 thin films by the TiN capping engineering

In the last decades, ferroelectricity has been discovered in Si-doped HfO 2 and Hf 1−x Zr x O 2 thin films, and the origin of ferroelectricity is considered to be the presence of the polar Pca2 1 orthorhombic phase. Recently, some investigations suggest that ZrO 2 thin films show ferroelectric behavior as well. As a well-known dopant capable of modulating ferroelectricity in HfO 2 thin films, Si-doping is applied up to approximately 5.3% to modify the ferroelectric properties of ZrO 2 films in this work. The atomic layer-deposited ZrO 2 films with a 45 nm thickness shows ferroelectric behavior with a remanent polarization of 7 μC/cm 2 after post-metallization annealing at 800 °C. According to Raman spectroscopy and grazing incidence X-ray diffraction structural characterizations, the amount of monoclinic and orthorhombic phases decreases, and the presence of the tetragonal phase increases by increasing the Si-doping content in the ZrO 2 films. The electrical properties both at room temperature and at lower temperature demonstrate antiferroelectric characteristics with lower remanent polarization and double hysteresis loops with Si incorporation in the 45 nm thick ZrO 2 films. An extrapolation of the Curie temperature for different Si-doping concentrations is obtained based on temperature-dependent remanent polarization measurements, showing evidence that Si dopants destabilize the polar ferroelectric phase. An increasing in-plane tensile strain with more Si-doping aids in stabilizing the tetragonal phase and leads to an improvement of antiferroelectric properties in 45 nm thick ZrO 2 .

Section: Introductionmentioning

confidence: 99%

Influence of Si-Doping on 45 nm Thick Ferroelectric ZrO₂ Films

Lomenzo

Kersch

et al. 2022

“…In the past decade, it has been reported that the TiN capping on Hf 0.5 Zr 0.5 O 2 thin films followed by the annealing at high temperatures induces the presence of the ferroelectric orthorhombic phase. − In our previous study, the PE/AFE/ferroelectric phase transition in ZrO 2 thin films was demonstrated by engineering, i.e., capping or removing, the TiN capping layer . However, the dependences of the dielectric properties of ZrO 2 on the TiN layer thickness and the chemical states at the interface were unclear.…”

Section: Introductionmentioning

confidence: 96%

“…26−29 In our previous study, the PE/AFE/ ferroelectric phase transition in ZrO 2 thin films was demonstrated by engineering, i.e., capping or removing, the TiN capping layer. 30 However, the dependences of the dielectric properties of ZrO 2 on the TiN layer thickness and the chemical states at the interface were unclear. In this study, the impacts of the TiN layer thickness, strain, and interfacial properties are investigated in detail to explore the origin of antiferroelectricity.…”

Section: ■ Introductionmentioning

confidence: 99%

Impact of a TiN Capping Layer on Phase Transformation and Capacitance Enhancement in ZrO₂

Wang

et al. 2021

Self Cite

Tailoring of crystalline phases and dielectric properties of ZrO2 thin films are demonstrated by capping a nanoscale TiN layer prepared by plasma-enhanced atomic layer deposition. The in-plane tensile strain induced by the TiN capping layer gives rise to the dramatic paraelectric-to-antiferroelectric phase transformation in ZrO2 and the significant capacitance enhancement up to 209%. The result is attributed to the formation of the ZrO2 tetragonal phase with the out-of-plane compressive strain due to TiN capping and the presence of interfacial TiO x N y , as revealed by nanobeam electron diffraction, X-ray diffraction, and X-ray photoelectron spectroscopy. The results demonstrate that the as-deposited TiN capping layer can effectively modulate the dielectric properties of nanoscale thin films without any postannealing treatment, which is very beneficial for the back-end-of-line process integration and numerous applications including supercapacitors, microelectromechanical systems, energy conversion, and nanoelectronics.

“…Furthermore, ZrO 2 is associated with the lowest material cost in an HfO 2 –ZrO 2 system and is thus suitable for use in the aforementioned applications. However, owing to the high thermal stability of the t-phase of ZrO 2 thin films, it is difficult to induce the o-phase without adopting the deposition method − and considering the surface structure of the bottom electrode . It was recently reported that the ferroelectricity of ZrO 2 could be demonstrated through the chemical solution deposition process and plasma-enhanced atomic layer deposition (PEALD). , Furthermore, it was reported that by performing PEALD in conjunction with the construction of the Pt surface structure, a large ferroelectricity comparable to a remanent polarization of approximately 50 μC/cm 2 could be achieved in an approximately 7 nm thick ZrO 2 film .…”

Section: Introductionmentioning

confidence: 99%

“…However, owing to the high thermal stability of the t-phase of ZrO 2 thin films, it is difficult to induce the o-phase without adopting the deposition method − and considering the surface structure of the bottom electrode . It was recently reported that the ferroelectricity of ZrO 2 could be demonstrated through the chemical solution deposition process and plasma-enhanced atomic layer deposition (PEALD). , Furthermore, it was reported that by performing PEALD in conjunction with the construction of the Pt surface structure, a large ferroelectricity comparable to a remanent polarization of approximately 50 μC/cm 2 could be achieved in an approximately 7 nm thick ZrO 2 film . The control of the crystalline phase and ferroelectricity through the post-deposition process has not been reported, despite its technological importance in expanding the range of processes for the application of ZrO 2 -based ferroelectrics.…”

Section: Introductionmentioning

confidence: 99%

Impact of Wet Annealing on Ferroelectric Phase Formation and Phase Transition of HfO₂–ZrO₂ System

Shibayama

Nagano

Asaka

et al. 2021

Wet annealing of the ZrO2 thin film can promote martensitic phase transition, leading to the formation of the ferroelectric orthorhombic (o-) phase. However, the present remanent polarization does not achieve the corresponding material potential of ferroelectric ZrO2. In this study, to enhance the ferroelectricity of ZrO2 thin films, the o-phase formation mechanism by wet annealing was presented considering the thermodynamics by systematically investigating the impact of wet annealing on the HfO2–ZrO2 solid solution for promoting phase transition. The structural analysis results indicated that wet annealing at low and high temperatures can promote the martensitic transition of Zr-rich Hf1–x Zr x O2 and Hf-rich Hf1–x Zr x O2, respectively. In addition, the Zr content exhibiting strong ferroelectricity increased from 0% (HfO2) to 66%. We performed a quantitative estimation of the phase deconvolution through polarization-electric field simulations, incorporating the depolarization field model. According to the change in the phase fraction by wet annealing, all results can be qualitatively and clearly understood based on the phase diagram of the HfO2–ZrO2 system. The impact of wet annealing pertains to the film-thinning effect, which tends to increase the thermodynamic driving force. Finally, we discuss possible solutions to suppress the film-thinning effect by introducing OH ions and improving ZrO2 ferroelectricity.