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Abstract

Since the discovery of ferroelectricity in HfO2 thin films [1], it obtained great research interest for the implementation into various integrated devices e.g. non-volatile memories or infrared sensors, due to its CMOS compatibility. As the ferroelectricity in HfO2 is assigned to the orthorhombic Pca21 phase [2], its phase fraction and orientation have a strong influence on the ferroelectric properties of the polycrystalline thin film. Due to the similar x-ray diffraction (XRD) pattern of the tetragonal and cubic phase, XRD analysis of the orthorhombic phase is strongly limited. Transmission Kikuchi diffraction (TKD) using a scanning electron microscope (SEM) is used for orientation mapping of nanostructured metals and is suggested to become an important technique for the characterization of nanocrystalline structures [3]. Here, we report the TKD analysis of Zr-doped HfO2 thin films. Therefore, the measured electron diffraction of dimpled samples are transformed into the Hough space and compared with the phases of HfO2 (see figure 1). This allows the mapping of the crystallographic phase and grain orientation which indicates a strong out-of-plane texture of the orthorhombic phase.
Crystallographic phase and orientation mapping of ferroelectric HfO2 thin
films by transmission Kikuchi diffraction
M. Lederer* 1, T. Kämpfe1, C. Mart1, T. Ali1, L. Roy1, K. Seidel1
1Fraunhofer IPMS, Königsbrücker Str. 178, 01099 Dresden, Germany
*e-mail: maximilian.lederer@ipms.fraunhofer.de
Abstract
Since the discovery of ferroelectricity in HfO2 thin films [1], it obtained great research interest for the
implementation into various integrated devices e.g. non-volatile memories or infrared sensors, due to its CMOS
compatibility. As the ferroelectricity in HfO2 is assigned to the orthorhombic Pca21 phase [2], its phase fraction
and orientation have a strong influence on the ferroelectric properties of the polycrystalline thin film. Due to the
similar x-ray diffraction (XRD) pattern of the tetragonal and cubic phase, XRD analysis of the orthorhombic
phase is strongly limited.
Figure 1. Phase identification of HfO2 by TKD. From the EBSD pattern contrast of each point, a quality map (a) can be
constructed. By comparing the EBSD patterns with simulated patterns from given phases (b), the phase can be identified and
a phase map (c) can be constructed.
Transmission Kikuchi diffraction (TKD) using a scanning electron microscope (SEM) is used for orientation
mapping of nanostructured metals and is suggested to become an important technique for the characterization of
nanocrystalline structures [3]. Here, we report the TKD analysis of Zr-doped HfO2 thin films. Therefore, the
measured electron diffraction of dimpled samples are transformed into the Hough space and compared with the
phases of HfO2 (see figure 1). This allows the mapping of the crystallographic phase and grain orientation which
indicates a strong out-of-plane texture of the orthorhombic phase.
Acknowledgments
We received funding within the ECSEL Joint Undertaking project WAKeMeUP in collaboration with the
European Union's H2020 Framework Program (H2020/2014-2020) and National Authorities, under grant
agreement number 783176. Furthermore, the work was supported by D. Goran from Bruker Nano Corporation.
References
[1] T.S. Böscke, J. Müller, D. Bräuhaus, U. Schröder, and U. Böttger, Appl. Phys. Lett. 2011, 99, 102903.
[2] X. Sang, E.D. Grimley, T. Schenk, U. Schroeder, and J.M. LeBeau, Appl. Phys. Lett. 2015, 106, 162905.
[3] P.W. Trimby, Ultramicroscopy 2012, 120, 16.
a)
b)
c)
Thesis
Full-text available
The discovery of ferroelectricity in hafnium oxide spurred a growing research field due to hafnium oxides compatibility with processes in microelectronics as well as its unique properties. Notably, its application in non-volatile memories, neuromorphic devices as well as piezo- and pyroelectric sensors is investigated. However, the behavior of ferroelectric hafnium oxide is not understood into depth compared to common perovskite structure ferroelectrics. Due the the metastable nature of the ferroelectric phase, process conditions have a strong influence during and after its deposition. In this work, the physical properties of hafnium oxide, process influences on the microstructure as well as reliability aspects in non-volatile and neuromorphic devices are investigated. With respect to the physical properties, strong evidence is provided that the antiferroelectric-like behavior in hafnium oxide based thin films is governed by ferroelastic 90° domain wall movement. Furthermore, the discovery of an electric field-induced crystallization process in this material system is reported. For the analysis of the microstructure, the novel method of transmission Kikuchi diffraction is introduced, allowing an investigation of the local crystallographic phase, orientation and grain structure. Here, strong crystallographic textures are observed in dependence of the substrate, doping concentration and annealing temperature. Based on these results, the observed reliability behavior in the electronic devices is explainable and engineering of the present defect landscape enables further optimization. Finally, the behavior in neuromorphic devices is explored as well as process and design guidelines for the desired behavior are provided.
  • T S Böscke
  • J Müller
  • D Bräuhaus
  • U Schröder
  • U Böttger
T.S. Böscke, J. Müller, D. Bräuhaus, U. Schröder, and U. Böttger, Appl. Phys. Lett. 2011, 99, 102903.
  • X Sang
  • E D Grimley
  • T Schenk
  • U Schroeder
  • J M Lebeau
X. Sang, E.D. Grimley, T. Schenk, U. Schroeder, and J.M. LeBeau, Appl. Phys. Lett. 2015, 106, 162905.
  • P W Trimby
P.W. Trimby, Ultramicroscopy 2012, 120, 16. a) b) c)