Substrate-dependent differences in ferroelectric behavior and phase diagram of Si-doped hafnium oxide

Maximilian Lederer,David Lehninger,Lukas M Eng,Tarek Ali,Thomas Kämpfe,Kati Kühnel,Ricardo Olivo,Konstantin Mertens,Konrad Seidel

doi:10.1557/s43578-021-00415-y

Abstract

Non-volatile memories based on ferroelectric hafnium oxide, especially the ferroelectric field-effect transistor (FeFET), have outstanding properties, e.g. for the application in neuromorphic circuits. However, material development has focused so far mainly on metal–ferroelectric–metal (MFM) capacitors, while FeFETs are based on metal–ferroelectric–insulator–semiconductor (MFIS) capacitors. Here, the influence of the interface properties, annealing temperature and Si-doping content are investigated. Antiferroelectric-like behavior is strongly suppressed with a thicker interface layer and high annealing temperature. In addition, high-k interface dielectrics allow for thicker interface layers without retention penalty. Moreover, the process window for ferroelectric behavior is much larger in MFIS capacitors compared to MFM-based films. This does not only highlight the substrate dependence of ferroelectric hafnium oxide films, but also gives evidence that the phase diagram of ferroelectric hafnium oxide is defined by the mechanical stress.Graphic

Highlights

The discovery of ferroelectricity in hafnium oxide [1], which is a gate material in the high-k metal gate complementary metal oxide semiconductor (CMOS) process technology, enabled the development of highly scaled ferroelectric field-effect transistors (FeFETs) for non-volatile memory application, e.g. in the 28 nm [2], 22 nm [3], or even smaller technology nodes [4]
Non-volatile memories based on ferroelectric hafnium oxide, especially the ferroelectric field-effect transistor (FeFET), have outstanding properties, e.g. for the application in neuromorphic circuits
This does highlight the substrate dependence of ferroelectric hafnium oxide films, and gives evidence that the phase diagram of ferroelectric hafnium oxide is defined by the mechanical stress

Summary

Introduction

The discovery of ferroelectricity in hafnium oxide [1], which is a gate material in the high-k metal gate complementary metal oxide semiconductor (CMOS) process technology, enabled the development of highly scaled ferroelectric field-effect transistors (FeFETs) for non-volatile memory application, e.g. in the 28 nm [2], 22 nm [3], or even smaller technology nodes [4]. Upon electric field-cycling, the observed Preisach density transits to 180°-domain wall movement (no peak splitting) and ferroelectric switching. A quite sharp transition is observable for MFM, forming a peak with a maximum around 2 at.% and reaching full AFE-like behavior ( 2PR ≈ 0 ) for the highest measured Si-concentration.

Results

Conclusion