Study on the internal field and conduction mechanism of atomic layer deposited ferroelectric Hf_0.5Zr_0.5O₂ thin films

Abstract

The internal field (E int ) in ferroelectric films is an important factor which can affect the reliability of practical devices utilizing two memory states which results from the remanent polarizations of ferroelectric films. In the current work, the E int in TiN/Hf 0.5 Zr 0.5 O 2 /TiN capacitors was controlled by changing the annealing atmosphere (N 2 , O 2 , and forming gas). The magnitude of negative E int in O 2 -annealed samples was the largest, whereas that in the forming gas-annealed sample was the smallest. The magnitude of E int can be understood based on the asymmetric distribution of oxygen vacancies near top and bottom TiN electrodes. Despite the large magnitude of E int , the two remanent polarizations can be reliably retained due to the large coercive electric field of Hf 0.5 Zr 0.5 O 2 films, and this is expected to be beneficial for application in semiconductor memory devices. During the repetitive electric field cycling for the wake-up process, the change in E int in O 2 -and forming gas-annealed samples showed the opposite tendency: the magnitude of E int in the O 2 -annealed Hf 0.5 Zr 0.5 O 2 film decreased, whereas that in the forming gas-annealed film increased. This difference is believed to be due to the redistribution of oxygen vacancies with electric field high enough for the migration of oxygen vacancies. The conduction mechanism of electrons through Hf 0.5 Zr 0.5 O 2 films was also examined, and the results fitted best with the Poole-Frenkel emission model with the shallow traps for all the samples with a reasonable optical dielectric constant value for Hf 0.5 Zr 0.5 O 2 .

A Comparative Study on the Ferroelectric Performances in Atomic Layer Deposited Hf0.5Zr0.5O2 Thin Films Using Tetrakis(ethylmethylamino) and Tetrakis(dimethylamino) Precursors

“…Thus, the difference in ε r value might be determined by the relative fractions of the tetragonal and orthorhombic phases or the defect concentration, which is expected to decrease the average dielectric constant with local lattice distortions. The ε r value of the tetragonal phase (35)(36)(37)(38)(39)(40) was higher than that of the orthorhombic phase (25)(26)(27)(28)(29)(30). Thus, the high ε r value of TEMA HZO capacitor indicates that it has a higher tetragonal phase fraction compared to the TDMA HZO capacitors.…”

Giant Negative Electrocaloric Effects of Hf0.5Zr0.5O2 Thin Films

“…From the spectra, it could be confirmed that the formation of a stable monoclinic phase was inhibited, and only the diffraction peaks of the tetragonal phase (t‐phase, space group: P 4 2 / nmc ) or the orthorhombic phase (o‐phase, space group: Pca 2 1 ) were observed for all films. The successful fabrication of a Pt/TiN/Hf x Zr 1− x O 2 /TiN capacitor could be confirmed from the TEM images . The Hf x Zr 1− x O 2 films were crystallized during a rapid thermal annealing process.…”

“…In the case of the ferroelectric Hf 0.5 Zr 0.5 O 2 films, a 150‐time field cycling with a 3.26 MV cm −1 pulse height and a 1 kHz frequency was performed before the P – E measurements to rule out a polarization increase due to the wake‐up effect . The P r value of the woken‐up state was as large as the values in the literature . This is abnormal behavior because the polarization of ferroelectrics generally decreases with increasing temperature, resulting in a positive ECE.…”

RETRACTED ARTICLE: Enhancement of the blue photoluminescence intensity for the porous silicon with HfO2 filling into microcavities

“…The ferroelectricity in HfO 2 films originates from the existence of the metastable and non-centrosymmetric orthorhombic phase with the space group of P ca2 1  1415. If crystallization occurs under mechanical encapsulation, the formation of the monoclinic phase is inhibited10, then the orthorhombic phase that shows a distinct piezoelectric response141617181920 will obtained. It is 600 ~ 700 °C for HfO 2 films crystallized according to previous reports21.…”