부산대학교 도서관

Hafnium oxide (Hf02) based ferroelectrics have gained significant attention as non-volatile ferroelectric random-access memories (FeRAM) due to its scalability and integrability in complementary metal oxide semiconductor (CMOS). To enable large scale FeRAM with CMOS integration, a large polarization at low temperature processing and low electric field is essential. Various reports show high polarization at the cost of high processing temperature and higher electric fields. In this paper, we report a low field (3.14 MV / cm) and large polarization (2Pr ~72 $\mu \mathrm{C}/\text{cm}2)$ in atomic layer deposition (ALD) grown (at 200 o C) ferroelectric Hf0.5Zr0.502 (HZO) thin film at lower post metallization annealing at 600o C. We discuss the impact of the source of oxygen from H20 precursor in ALD process in creating O-vacancies during deposition with X-Ray diffraction analysis (XRD). Then we discuss the role of low thermal expansion coefficient of tungsten (W) as top and bottom electrode to induce in -plane tensile strain during annealing to enhance orthorhombic phase (o-phase) - essential to get high polarization. A high dielectric constant $\varepsilon \mathrm{r}\sim 42$ at −3V shows the improved quality of the ferroelectric film. Finally, we discuss the impact of electric field and frequency on the polarization.