Thermally Stable and Radiation Hard Ferroelectric Hf_0.5Zr_0.5O₂ Thin Films on Muscovite Mica for Flexible Nonvolatile Memory Applications

Metal–ferroelectric–metal (MFM) capacitors on flexible substrates are promising for flexible nonvolatile memory applications, while the insufficient scalability of perovskite-based ferroelectric thin films and the difficulty of direct integration of high performance ferroelectric thin films on current conventional flexible substrates are the most serious obstacles to their practical applications. Meanwhile, performance under harsh conditions (such as high temperature and high total ionized dose (TID) radiation) is highly demanded due to the growing applications for nonvolatile memory. Here, we integrate highly scalable ferroelectric Hf0.5Zr0.5O2 (HZO) thin films on potential flexible mica substrates using atomic layer deposition (ALD) to form flexible MFM capacitors and investigate the ferroelectric properties, the retention behaviors, and endurance characteristics of the TaN/HZO/TaN/mica flexible MFM capacitors under various tensile and compressive bending radii. In addition, these characteristics of the HZO-based MFM flexible capacitors are explored in a wide temperature range from 25 up to 125 °C. The ferroelectricity of the film can be retained under a bending radius down to 7.5 mm after 1000 bending cycles, and the retention properties can be reserved under a bake time of 104 s at 125 °C, with an extrapolated retention time-to-failure longer than 10 years. Furthermore, the flexible devices display robust ferroelectric performance against radiation of 60Co γ-rays with a total dose of 1 Mrad (Si). Our work represents a critical step in HfO2-based ferroelectric memory implemented on mica toward flexible nonvolatile memory operated under harsh conditions.