Tensile stress regulated microstructures and ferroelectric properties of Hf0.5Zr0.5O2 films

The discovery of ferroelectricity in HfO2 based materials reactivated the research on ferroelectric memory. However, the complete mechanism underlying its ferroelectricity remains to be fully elucidated. In this study, we conducted a systematic study on the microstructures and ferroelectric properties of Hf0.5Zr0.5O2 (HZO) thin films with various annealing rates in the rapid thermal annealing. It was observed that the HZO thin films with higher annealing rates demonstrate smaller grain size, reduced surface roughness and a higher portion of orthorhombic phase. Moreover, these films exhibited enhanced polarization values and better fatigue cycles compared to those treated with lower annealing rates. The grazing incidence x-ray diffraction measurements revealed the existence of tension stress in the HZO thin films, which was weakened with decreasing annealing rate. Our findings revealed that this internal stress, along with the stress originating from the top/bottom electrode, plays a crucial role in modulating the microstructure and ferroelectric properties of the HZO thin films. By carefully controlling the annealing rate, we could effectively regulate the tension stress within HZO thin films, thus achieving precise control over their ferroelectric properties. This work established a valuable pathway for tailoring the performance of HZO thin films for various applications.