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 O2 plasma as oxidants, respectively, and a post-metallization annealing (PMA) was performed at 300–400 °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 Å with an increase in PMA temperature, while the d-spacing estimated by conventional x-ray diffraction was 2.92 Å regardless of the PMA temperature. The remanent polarization (2Pr = Pr+ − Pr−) of the HZO films increased as the PMA temperature increased. It is clear that the 2Pr 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 °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 (103 cycles), pristine (100 cycle), and fatigue (107 cycles) states, respectively. Therefore, an analysis of the ferroelectric O phase is very important for understanding the ferroelectricity including endurance.