A Comprehensive Study on the Effect of TiN Top and Bottom Electrodes on Atomic Layer Deposited Ferroelectric Hf0.5Zr0.5O2 Thin Films.

Si Joon Kim,Harrison Sejoon Kim,Chadwin D Young,Rino Choi,Akshay Sahota,Kihyun Kim,Pil-Ryung Cha,Su Min Hwang,Jaidah Mohan,Yong Chan Jung,Jinho Ahn,Jiyoung Kim,Hyun-Yong Yu,Namhun Kim

doi:10.3390/ma13132968

Abstract

The discovery of ferroelectricity in HfO2-based materials in 2011 provided new research directions and opportunities. In particular, for atomic layer deposited Hf0.5Zr0.5O2 (HZO) films, it is possible to obtain homogenous thin films with satisfactory ferroelectric properties at a low thermal budget process. Based on experiment demonstrations over the past 10 years, it is well known that HZO films show excellent ferroelectricity when sandwiched between TiN top and bottom electrodes. This work reports a comprehensive study on the effect of TiN top and bottom electrodes on the ferroelectric properties of HZO thin films (10 nm). Investigations showed that during HZO crystallization, the TiN bottom electrode promoted ferroelectric phase formation (by oxygen scavenging) and the TiN top electrode inhibited non-ferroelectric phase formation (by stress-induced crystallization). In addition, it was confirmed that the TiN top and bottom electrodes acted as a barrier layer to hydrogen diffusion into the HZO thin film during annealing in a hydrogen-containing atmosphere. These features make the TiN electrodes a useful strategy for improving and preserving the ferroelectric properties of HZO thin films for next-generation memory applications.

Highlights

The observation of unexpected ferroelectric properties in atomic layer deposited HfO2 -based films in 2011 provided a pathway for new research directions and opportunities [1]
In this study, the same RTA process was performed after depositing the TiN bottom electrode to investigate only the stress caused by the TiN top electrode during HZO crystallization
It was confirmed that this feature works regardless deposited TiN top electrode was found to inhibit the non-ferroelectric m-phase formation by stressinduced crystallization during the RTA process

Summary

Introduction

The observation of unexpected ferroelectric properties in atomic layer deposited HfO2 -based films in 2011 provided a pathway for new research directions and opportunities [1]. It has been demonstrated that the thickness range of the feasible ferroelectric performance of HZO film can be reduced to 5 nm [4,5] In this regard, numerous studies have been reported in various fields, such as ferroelectric random-access memory (FRAM), ferroelectric field-effect transistors, synaptic devices, and energy storage applications [6,7,8]. It was found that the applied stress depends on the type of electrode due to the difference in the thermal expansion coefficient [7,11] In this regard, the influence of the top and bottom electrodes on HZO crystallization has been intensively studied, including the various electrode materials, the surface/interface effects, the capping layer effects, etc. Based on experiment demonstrations from the past 10 years, it has been established that HZO films exhibit excellent ferroelectricity in structures sandwiched with

Methods

Results

Conclusion