A perspective on semiconductor devices based on fluorite-structured ferroelectrics from the materials–device integration perspective

Abstract

Ferroelectric materials are known to be ideal materials for nonvolatile memory devices, owing to their two electrically switchable spontaneous polarization states. However, difficulties in scaling down devices with ferroelectric materials have hindered their practical applications and research. The discovery of ferroelectricity in fluorite-structured ferroelectrics has revived research on semiconductor devices based on ferroelectrics. With their scalability and established fabrication techniques, the performance of nanoscale electronic devices with fluorite-structured ferroelectrics is being rapidly developed. However, the fundamental physics behind the superior ferroelectricity is yet to be elucidated. From this Perspective, the status of research on fluorite-structured ferroelectrics and state-of-the-art semiconductor devices based on them are comprehensively reviewed. In particular, the fundamental physics of fluorite-structured oxides is critically reviewed based on a newly developed theory as well as on the classical theory on ferroelectrics. A perspective on the establishment of emerging semiconductor devices based on fluorite-structured ferroelectrics is provided from the viewpoint of materials science and engineering.

Epitaxial Ferroelectric HfO2 Films: Growth, Properties, and Devices

“…The recent discovery of ferroelectricity in simple oxides based on HfO 2 has renewed the interest in ferroelectric memories. − HfO 2 is already used in CMOS lines and the deposition techniques and conditions to form the ferroelectric phase can be compatible with CMOS technology. Very shortly after the first publication in 2011 reporting on ferroelectricity in HfO 2 , prototypes of Fe-RAMs and Fe-FETs were produced.…”

“…Progress in the preparation, understanding of structural and ferroelectric properties of HfO 2 , and fabrication of devices has been enormous (see, for instance, reviews in refs − and − ). This progress has been achieved mainly with polycrystalline films.…”

Defects in ferroelectric HfO2

“…14 The benchmark of modern ferroelectric HfO 2 technology in terms of various device parameters, also compared to perovskite ferroelectric oxides, can be found in recent reviews. 15,16 Even though over the years the successful implementation of different ferroelectric HfO 2 based memory devices has been demonstrated, none of them has been commercialized so far. The challenge, which has always been an issue for ferroelectric memories and still remains for ferroelectric HfO 2 , is the reliability of devices.…”

Impact of Wet Annealing on Ferroelectric Phase Formation and Phase Transition of HfO2–ZrO2 System

“…HfO 2 , ZrO 2 , and their solid-solution system Hf 1– x Zr x O 2 have been extensively studied experimentally and theoretically for application in memory devices such as ferroelectric random access memory, ferroelectric tunnel junctions, and ferroelectric field-effect transistors, − steep slope transistors based on the negative capacitance effect, , and energy-related devices − since the ferroelectricity of Si-doped HfO 2 was first discovered . The ferroelectricity of these materials appears in the noncentrosymmetric orthorhombic ( Pca 2 1 , o-) phase, which has been demonstrated through experiments and theoretical calculations. − This ferroelectric o-phase is a metastable phase that appears in the thin-film region and does not exist in the bulk phase of the HfO 2 –ZrO 2 system.…”