Since the first report on the unexpected ferroelectricity of fluorite-structure oxides in 2011, this topic has provided a pathway for new research directions and opportunities. Based on theoretical calculations and experimental demonstrations, it is now well known that fluorite-structure ferroelectrics are compatible with complementary metal-oxide-semiconductor technology and exhibit ferroelectric properties at extremely thin (<10 nm) thicknesses. It should be noted that the noncentrosymmetric orthorhombic phase, which is responsible for ferroelectric behavior, is formed even at low temperatures (400 C or less). Herein, the various factors such as doping effects, deposition method, annealing method and conditions, and substrate material are reviewed, focusing on thermal budget, especially the low-temperature annealing process for formation of the ferroelectric phase. These low-thermal-budget processes facilitate not only the integration of ferroelectric circuits in the back-end-of-line to increase the effective memory area and add more functionalities but also applications for flexible and wearable electronics.

In article number http://doi.wiley.com/10.1002/pssr.202100028, Jiyoung Kim, Si Joon Kim, and co‐workers comprehensively review the various factors such as doping effects, deposition method, annealing method and conditions, and substrate material for obtaining fluorite‐structure ferroelectrics with low‐thermal‐budget processes (400 °C or less). These low‐thermal‐budget processes facilitate not only the integration of ferroelectric circuits in the back‐end‐of‐line, but also the applications to flexible and wearable electronics.

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