Correlation between ferroelectricity and ferroelectric orthorhombic phase of HfxZr1-xO2 thin films using synchrotron x-ray analysis

The change in the interplanar spacing (d-spacing) including the ferroelectric orthorhombic (O) phase in the low-temperature fabricated HfxZr1-xO2 (HZO) films was studied using synchrotron grazing-incidence wide-angle x-ray scattering analysis. The 10-nm-thick HZO films were fabricated by thermal and plasma-enhanced atomic layer deposition (TH- and PE-ALD) methods using H2O gas and O-2 plasma as oxidants, respectively, and a post-metallization annealing (PMA) was performed at 300-400 degrees C. The d-spacing of the mixture of (111)-, (101)-, and (111)-planes of O, tetragonal (T), and cubic (C) phases, respectively, for the TH- and PE-ALD HZO films increased up to 2.99 angstrom with an increase in PMA temperature, while the d-spacing estimated by conventional x-ray diffraction was 2.92 angstrom regardless of the PMA temperature. The remanent polarization (2P(r) = P-r(+) - P-r(-)) of the HZO films increased as the PMA temperature increased. It is clear that the 2P(r) value satisfied a linear relationship as a function of the d-spacing of O(111)/T(101)/C(111) phases. Furthermore, the wake-up effect was found to depend on the ferroelectric O phase formation. The wake-up effect was significantly reduced in both the TH- and PE-ALD HZO films after the PMA at 400 degrees C due to the increase in the ferroelectric O phase formation. The leakage current density (J)-electric field properties of the PE-ALD HZO film with the lowest d-spacing were divided into three steps, such as low, middle, and large J values, in the wake-up (10(3) cycles), pristine (10(0) cycle), and fatigue (10(7) cycles) states, respectively. Therefore, an analysis of the ferroelectric O phase is very important for understanding the ferroelectricity including endurance.

Automated summary

The study investigated the change in interplanar spacing (d-spacing) of the ferroelectric orthorhombic (O) phase in low-temperature fabricated HfxZr1-xO2 (HZO) films. It was found that an increase in post-metallization annealing (PMA) temperature led to higher remanent polarization (2P(r)) values and a linear relationship between 2P(r) and the d-spacing of O/T/C phases. The presence of a ferroelectric O phase was crucial for the wake-up effect, which was reduced after PMA at 400 degrees C in both thermal and plasma-enhanced atomic layer deposition (ALD) HZO films. The analysis of the ferroelectric O phase is important for understanding ferroelectricity and endurance in the films.