Impact of annealing temperature on the ferroelectric properties of W/Hf_0.5Zr_0.5O₂/W capacitor

Abstract Crystallization annealing is a crucial process for the formation of ferroelectric phase in HfO2-based ferroelectric thin films. Here, we systematically investigate the impact of annealing process, with temperature varied from 350 ℃ to 550 ℃, on the electricity, ferroelectricity, and reliability of Hf0.5Zr0.5O2 (HZO~7.5 nm) film capacitor. It was found that HZO film annealed at a low temperature of 400℃ can effectively suppress formation of m-phase and reduce the leakage current. The 400 ℃ annealed-HZO film also exhibited preferable ferroelectric properties than that annealed at 350℃ and 550 ℃. Specifically, the 400 ℃-annealed HZO film shows outstanding 2 P r value of 54.6 μC/cm2 at ±3.0 MV/cm, which is relatively high among that of previously reported on HZO film under the same electric field and annealing temperature. When the applied electric field increases to ± 5.0 MV/cm, its 2 P r value can reach a maximum value of 69.6 μC/cm2. In addition, both the 400 ℃ and 550 ℃-annealed HZO film can endure up to ~2.3×108 cycles under a cycling field of 2.0 MV/cm before the occurrence of breakdown. The 72.1% of initial polarization is maintained for 400 ℃-annealed HZO film, while only 44.9% is maintained for 550 ℃-annealed HZO film. Our work demonstrated that HZO film with low crystallization temperature (400 °C) has considerably high ferroelectric polarization, which is significantly important in the applications of ferroelectric memory and negative capacitance transistors.