基于Cu和TiN盖层的Hf0.5Zr0.5O2薄膜铁电性能比较研究

A Comparative Study on the Ferroelectric Properties of Hf0.5Zr0.5O2 Thin Films by Using Cu and TiN Capping Layers

该文采用原子层沉积在Si/SiO2/TiN基底上制备了20 nm Hf0.5Zr0.5O2(HZO)薄膜,并分别以TiN和Cu为盖层构筑了HZO铁电电容器.掠入射X射线衍射测试表明,TiN和Cu作为盖层的HZO薄膜都具有明显的正交相.系统比较研究了Cu和TiN盖层对HZO薄膜的铁电、漏电和可靠性的影响.极化-电压测试表明,TiN和Cu为盖层的HZO薄膜在±4 V扫描电压下,剩余极化强度(2Pr)值分别为40.4μC/cm^2和21.2μC/cm^2.相应的矫顽电压分别为+1.7 V和+2.0 V.极化疲劳与保持特性测试表明,在经过2.3×10^8循环次数后,以TiN和Cu为盖层的HZO薄膜的2 P r值分别衰减了39.7%和45.6%.经过1.3×10^4 s保持测试,TiN和Cu盖层的HZO薄膜的2 P r值从初始34.4μC/cm^2和17.1μC/cm^2分别下降到了22.6μC/cm^2和1.6μC/cm^2.上述结果说明,金属盖层是影响HZO铁电性的一个非常重要的因素.盖层的功函数、热膨胀系数、界面缺陷和界面介电层都是导致HZO薄膜铁电性差异的可能机制.该文工作对于进一步理解HZO铁电性起源和影响机制提供了有意义的借鉴,将有助于发展未来高性能的HZO铁电存储器和负电容晶体管.

In this paper,we successfully deposited 20 nm Hf0.5Zr0.5O2(HZO)thin films on Si/SiO2/TiN substrates by atomic layer deposition.The ferroelectricity of the HZO thin films with TiN and Cu capping layers(CLs)were investigated through metal/HZO/metal capacitors.The grazing incidence X-ray diffraction test shows that HZO thin films with TiN and Cu CLs have obvious orthorhombic phases.We also carried out a systematic investigation on the effects of Cu and TiN CLs on ferroelectricity,leakage current and reliability of HZO thin films.The polarization-voltage characterization shows that the remnant polarization(2Pr)values of HZO thin films with TiN and Cu CLs at±4 V scanning voltage are 40.4μC/cm^2 and 21.2μC/cm^2,respectively.The corresponding coercive voltages are+1.7 V and+2.0 V,respectively.In addition,the endurance test showed that the 2 P r values of HZO thin films with TiN and Cu CLs decreased by 39.7%and 45.6%after 2.3×10^8 program/erase cycles,respectively.After 1.3×10^4 s retention test,the 2Pr values of HZO thin films with TiN and Cu caps decreased from 34.4μC/cm^2 and 17.1μC/cm^2 tO22.6μC/cm^2 and 1.6μC/cm^2,respectively.The above results indicate that metal capping layer plays important role on the ferroelectric properties of HZO thin films.The different capping layer may have different work functions,thermal expansion coefficients,interface defects,and interfacial dielectric layer,which are possible mechanisms to affect the ferroelectric properties of HZO thin films.The present work provides useful insights for further understanding the origin and corresponding mechanisms to affect the ferroelectricity of HZO thin films,and will contribute to the development of high performance HZO-based ferroelectric memory and negative capacitor transistor in the future.