Dramatic impact of pressure and annealing temperature on the properties of sputtered ferroelectric HZO layers

Jordan Bouaziz,Lucian Pintilie,Pedro Rojo Romeo,Nicolas Baboux,Bertrand Vilquin,Raluca Negrea

doi:10.1063/1.5110894

Abstract

The crystallization of ferroelectric (Hf,Zr)O2 thin films is achieved by playing on the deposition pressure during reactive magnetron sputtering from a Hf/Zr metallic target. Postdeposition annealing was tried at different temperatures in order to optimize the quality of the samples. Structural characterizations are performed by transmission electron microscopy (TEM) and electrical characterizations are carried out. TEM analyses reveal that the samples deposited at a low working pressure show no orthorhombic phase, and thus are not ferroelectric, whereas the samples deposited at higher working pressure show the orthorhombic ferroelectric phase. The maximum remnant polarization is 6 µC/cm2 and is obtained for the sample annealed at 600 °C. The maximum cycles to breakdown is higher than 2 × 1010 cycles and is reached for the sample annealed at 400 °C. These results are discussed in the matter of phase transition and oxygen vacancies redistribution.

Highlights

The discovery of ferroelectricity in Si-doped HfO2 has been published in 2011 by Böscke et al.1 many publications have been written on the subject
We investigate the (Hf, Zr)O2 layers capped between two TiN electrodes deposited by reactive magnetron sputtering
The samples have been analyzed by transmission electron microscopy (TEM) with low magnification, HRTEM and selected area electron diffraction (SAED)

Summary

INTRODUCTION

The discovery of ferroelectricity in Si-doped HfO2 has been published in 2011 by Böscke et al. many publications have been written on the subject. In their 2018 review, Park et al. presented a figure showing the impressively growing number of articles dealing with this subject The reason for this success is due to the fact that ferroelectricity, in this family of materials, has the advantage to be theoretically optimized for a film thickness of 10 nm. Electrical characterizations are carried out in order to compare with literature the change of the remnant polarization Pr as a function of the number of applied electrical field cycling. This change is characterized by the wake-up effect, the fatigue, and the breakdown

Fabrication

Characterization

TEM Structural Characterization

Electrical Characterizations

CONCLUSION