Impact of vacancies and impurities on ferroelectricity in PVD- and ALD-grown HfO2 films

Lutz Baumgarten,Thomas Mikolajick,Terence Mittmann,Monica Materano,Thomas Szyjka,Christoph Schlueter,Uwe Schroeder,Martina Müller,Yury Matveyev

doi:10.1063/5.0035686

Abstract

We investigate the emerging chemical states of TiN/HfO2/TiN capacitors and focus especially on the identification of vacancies and impurities in the ferroelectric HfO2 layers, which are produced either by physical vapor deposition (PVD) or atomic layer deposition (ALD). Depending on the specific growth conditions, we identify different mechanisms of oxygen vacancy formation. Corresponding spectral features are consistently observed for all HfO2- and TiN-related core levels by hard x-ray photoelectron spectroscopy (HAXPES). In ALD-grown samples, we find spectral signatures for the electronic interaction between oxygen vacancies and nitrogen impurities. By linking the HAXPES results to electric field cycling experiments on the TiN/HfO2/TiN capacitors, we discuss possible formation mechanisms and stabilization of the ferroelectric HfO2 phase directly related to specific PVD or ALD conditions.

Highlights

As an alternative technique, physical vapor deposition (PVD) by sputtering from an HfO2 target was explored to gain even better control on the stoichiometry and defect concentration in HfO2 thin films
We investigate the emerging chemical states of TiN/HfO2/TiN capacitors and focus especially on the identification of vacancies and impurities in the ferroelectric HfO2 layers, which are produced either by physical vapor deposition (PVD) or atomic layer deposition (ALD)
By linking the hard x-ray photoelectron spectroscopy (HAXPES) results to electric field cycling experiments on the TiN/HfO2/TiN capacitors, we discuss possible formation mechanisms and stabilization of the ferroelectric HfO2 phase directly related to specific PVD or ALD conditions

Summary

Introduction

Physical vapor deposition (PVD) by sputtering from an HfO2 target was explored to gain even better control on the stoichiometry and defect concentration in HfO2 thin films. It should be noted that we observe these binding energy shifts between PVD- and ALD-grown samples in all spectral features, which are related to the HfO2 layer ( see the supplementary material).

Results

Conclusion