Effect of Al₂O₃ interlayer on ferroelectric properties of Hf_0.5Zr_0.5O₂ thin film capacitors

HZO-based ferroelectric thin films exhibit compatibility with traditional complementary metal-oxide-semiconductor (CMOS) semiconductor processing technology. These materials are not only extensively utilized as chip insulating layers but also, due to their remarkable ferroelectric properties even at thicknesses below 10 nm, have emerged as a pivotal candidate for next-generation ferroelectric memory applications. Nevertheless, conventional HZO films generally necessitate high annealing temperatures (exceeding 400 ℃) to stabilize the orthorhombic phase responsible for ferroelectricity, thereby restricting their integration into CMOS processes. In this study, an Al₂O₃ interlayer was incorporated above the HZO ferroelectric layer, and a TiN/HZO/Al₂O₃/TiN/Pt ferroelectric capacitor structure was fabricated. The influence of the Al₂O₃ interlayer on the ferroelectric characteristics of HZO films was investigated systematically. The findings demonstrate that, at an annealing temperature of 350 ℃, a 1 nm thick Al₂O₃ interlayer enhances the double remanent polarization of the device by approximately fivefold, reaching 19.3 μC·cm⁻². Furthermore, this ferroelectric memory device exhibits a "wake-up-free" behavior and demonstrates exceptional write-erase endurance (≥10⁹ cycles at 3.5 MV·cm⁻¹). Consequently, the Al₂O₃ interlayer serves to augment remanent polarization, reduce the coercive field, and decrease the required annealing temperature, facilitating high-performance ferroelectric memory operation at reduced thermal budgets.