ZnO和铪锆氧化物(Hf_(0.5)Zr_(0.5)O_(2))堆栈能带对准研究

Energy Band Alignment Study on ZnO and Hafnium Zirconium Oxide(Hf_(0.5)Zr_(0.5)O_(2))Stack

铪锆氧化物(HZO)克服了传统铁电材料的缺陷,能够与CMOS工艺兼容,并且可以微缩,在高端芯片领域有很大的发展潜力。而其瓶颈在于循环寿命低,主流研究试图通过界面工程、介质掺杂等工艺改善其铁电性能并提高其寿命。本工作提出了以ZnO作为HZO与上电极的过渡层,制备HZO/ZnO堆栈,并通过X射线光电子能谱研究了ZnO过渡层与HZO的基本物理问题,即二者的能带结构和退火对能带对准的影响。结果表明,退火过程中界面处发生了元素扩散和偶极子的改变,使HZO/ZnO的能带偏移发生变化,异质结由type-Ⅱ型变为type-Ⅰ型。本工作将为HZO存储器的改善寿命的ZnO过渡层提供基础物理学依据。

Hf_(0.5)Zr_(0.5)O_(2)overcomes the defects of traditional ferroelectric materials.It is compatible with CMOS processing and is scalable,which makes it a great development potential in high-end chip field.The bottleneck of HZO is the low cycle life.Most of researchers attempt to improve its ferroelectric properties and extend its lifespan through interface engineering,dielectric miscellaneous and other arts and crafts.ZnO is used as a transition layer between HZO and top electrode and the HZO/ZnO stacks are fabricated.The fundamental physical aspects of the ZnO transition layer and its interface with HZO,including the energy band structure and the impact of annealing on energy band alignment are studied by using X-ray photoelectron spectroscopy.The results indicate that element diffusion and dipole moments change occur at the interface during the annealing process,resulting in a variation of the energy band offset in HZO/ZnO,and a transition of the heterojunction from type-Ⅱ to type-Ⅰ.This work provides a fundamental physical basis for ZnO transition layer in improving the lifespan of HZO-based memories.