Effect of ferroelectric and interface films on the tunneling electroresistance of the Al2O3/Hf0.5Zr0.5O2 based ferroelectric tunnel junctions. (8th September 2021)

• Record Type: Journal Article
• Authors: Shekhawat, Aniruddh; Hsain, H Alex; Lee, Younghwan; Jones, Jacob L; Moghaddam, Saeed
• Is Part Of: Nanotechnology. Volume 32:Number 48(2021)
• Publication Date: 2021-09-08
• Subjects: ferroelectrics -- hafnium oxide -- interface engineering -- atomic layer deposition -- tunnel junctions; Nanotechnology -- Periodicals; Nanotechnology -- Periodicals; Nanotechnology; Publications périodiques; Nanotechnologies; Periodicals; 620.5
• DOI: 10.1088/1361-6528/ac1ebe
• Languages: English
• ISSNs: 0957-4484

Abstract

Abstract: Ferroelectric random-access memory (FRAM) based on conventional ferroelectric materials is a non-volatile memory with fast read/write operations, high endurance, and 10 years of data retention time. However, it suffers from destructive read-out operation and lack of CMOS compatibility. HfO2 -based ferroelectric tunnel junctions (FTJ) may compensate for the shortcomings of FRAM by its CMOS compatibility, fast operation speed, and non-destructive readout operation. In this study, we investigate the effect of ferroelectric and interface film thickness on the tunneling electroresistance or ON/OFF current ratio of the Hf0.5 Zr0.5 O2 /Al2 O3 based FTJ device. Integrating a thick ferroelectric layer (i.e. 12 nm Hf0.5 Zr0.5 O2 ) with a thin interface layer (i.e. 1 nm Al2 O3 ) resulted in an ON/OFF current ratio of 78. Furthermore, to elucidate the relationship between ON/OFF current ratio and interfacial properties, the Hf0.5 Zr0.5 O2 -Al2 O3 films and Ge-Al2 O3 interfaces are examined via time-of-flight secondary ion mass spectrometry depth profiling mode. A bilayer oxide heterostructure (Hf0.5 Zr0.5 O2 /Al2 O3 ) is deposited by atomic layer deposition (ALD) on the Ge substrate. The ON/OFF current ratio is enhanced by an order of magnitude when the Hf0.5 Zr0.5 O2 film deposition mode is changed from exposure (H2 O) ALD to sequential plasma (sequential O2 –H2 ) ALD. Moreover, the interfacial engineering approach based on the in situ ALD H2 -plasma surface pre-treatment of Ge increases the ON/OFF current ratio from 9 to 38 by reducing the interfacial trap density state at the Ge-Al2 O3 interface and producing Al2 O3 with fewer oxygen vacancies as compared to the wet etch (HF + H2 O rinse) treatment of the Ge substrate. This study provides evidence of strong coupling between Hf0.5 Zr0.5 O2 and Al2 O3 films in controlling the ON/OFF current ratio of the FTJ.