Shekhawat Aniruddh, Hsain H Alex, Lee Younghwan, Jones Jacob L, Moghaddam Saeed
Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL, 32611, United States of America.
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC, 27695, United States of America.
Nanotechnology. 2021 Sep 8;32(48). doi: 10.1088/1361-6528/ac1ebe.
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. HfO-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 HfZrO/AlObased FTJ device. Integrating a thick ferroelectric layer (i.e. 12 nm HfZrO) with a thin interface layer (i.e. 1 nm AlO) resulted in an ON/OFF current ratio of 78. Furthermore, to elucidate the relationship between ON/OFF current ratio and interfacial properties, the HfZrO-AlOfilms and Ge-AlOinterfaces are examined via time-of-flight secondary ion mass spectrometry depth profiling mode. A bilayer oxide heterostructure (HfZrO/AlO) 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 HfZrOfilm deposition mode is changed from exposure (HO) ALD to sequential plasma (sequential O-H) ALD. Moreover, the interfacial engineering approach based on theALD H-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-AlOinterface and producing AlOwith fewer oxygen vacancies as compared to the wet etch (HF + HO rinse) treatment of the Ge substrate. This study provides evidence of strong coupling between HfZrOand AlOfilms in controlling the ON/OFF current ratio of the FTJ.
基于传统铁电材料的铁电随机存取存储器（FRAM）是一种非易失性存储器，具有快速读/写操作、高耐久性和10年的数据保留时间。然而，它存在破坏性读出操作以及缺乏与CMOS兼容性的问题。基于HfO的铁电隧道结（FTJ）可能通过其CMOS兼容性、快速操作速度和非破坏性读出操作来弥补FRAM的缺点。在本研究中，我们研究了铁电层和界面膜厚度对基于HfZrO/AlO的FTJ器件的隧穿电阻或开/关电流比的影响。将厚铁电层（即12 nm HfZrO）与薄界面层（即1 nm AlO）相结合，得到的开/关电流比为78。此外，为了阐明开/关电流比与界面性质之间的关系，通过飞行时间二次离子质谱深度剖析模式对HfZrO-AlO薄膜和Ge-AlO界面进行了研究。通过原子层沉积（ALD）在Ge衬底上沉积双层氧化物异质结构（HfZrO/AlO）。当HfZrO薄膜沉积模式从曝光（HO）ALD变为顺序等离子体（顺序O-H）ALD时，开/关电流比提高了一个数量级。此外，基于Ge的ALD H等离子体表面预处理的界面工程方法，通过降低Ge-AlO界面处的界面陷阱密度状态，并与Ge衬底的湿法蚀刻（HF + HO冲洗）处理相比，产生具有更少氧空位的AlO，将开/关电流比从9提高到38。本研究提供了HfZrO和AlO薄膜在控制FTJ的开/关电流比方面存在强耦合的证据。
