Ferroelectric Hf₀․₅Zr₀․₅O₂ Thin Films: A Review of Recent Advances

Ferroelectricity in HfO₂-based materials, especially Hf₀․₅Zr₀․₅O₂ (HZO), is today one of the most attractive topics because of its wide range of applications in ferroelectric random-access memory, ferroelectric field-effect transistors, ferroelectric tunneling junctions, steep-slope devices, and synaptic devices. The main reason for this increasing interest is that, when compared with conventional ferroelectric materials, HZO is compatible with complementary metal-oxide-semiconductor flow [even back-end of the line thermal budget] and can exhibit robust ferroelectricity even at extremely thin (<10nm) thicknesses. In this report, recent advances in the ferroelectric properties of HZO thin films since the first report in 2011, including doping effects, mechanical stress effects, interface effects, and ferroelectric film thickness effects, are comprehensively reviewed.