HfO_(2)基铁电薄膜的结构、性能调控及典型器件应用

Structure,performance regulation and typical device applications of HfO_(2)-based ferroelectric films

大数据、物联网和人工智能的快速发展对存储芯片、逻辑芯片和其他电子元器件的性能提出了越来越高的要求.本文介绍了HfO_(2)基铁电薄膜的铁电性起源,通过掺杂元素改变晶体结构的对称性或引入适量的氧空位来降低相转变的能垒可以增强HfO_(2)基薄膜的铁电性,在衬底和电极之间引入应力、减小薄膜厚度、构建纳米层结构和降低退火温度等方法也可以稳定铁电相.与钙钛矿氧化物铁电薄膜相比, HfO_(2)基铁电薄膜具有与现有半导体工艺兼容性更强和在纳米级厚度下铁电性强等优点.铁电存储器件理论上可以达到闪存的存储密度,读写次数超过1010次,同时具有读写速度快、低操作电压和低功耗等优点.此外,还总结了HfO_(2)基薄膜在负电容晶体管、铁电隧道结、神经形态计算和反铁电储能等方面的主要研究成果.最后,讨论了HfO_(2)基铁电薄膜器件当前面临的挑战和未来的机遇.

The rapid developments of big data,the internet of things,and artificial intelligence have put forward more and more requirements for memory chips,logic chips and other electronic components.This study introduces the ferroelectric origin of HfO_(2)-based ferroelectric film and explains how element doping,defects,stresses,surfaces and interfaces,regulate and enhance the ferroelectric polarization of the film.It is widely accepted that the ferroelectricity of HfO_(2)-based ferroelectric film originates from the metastable tetragonal phase.The ferroelectricity of the HfO_(2)-based film can be enhanced by doping some elements such as Zr,Si,Al,Gd,La,and Ta,thereby affecting the crystal structure symmetry.The introduction of an appropriate number of oxygen vacancy defects can reduce the potential barrier of phase transition between the tetragonal phase and the monoclinic phase,making the monoclinic phase easy to transition to tetragonal ferroelectric phase.The stability of the ferroelectric phase can be improved by some methods,including forming the stress between the substrate and electrode,reducing the film thickness,constructing a nanolayered structure,and reducing the annealing temperature.Compared with perovskite oxide ferroelectric thin films,HfO_(2)-based films have the advantages of good complementary-metal-oxide-semiconductor compatibility and strong ferroelectricity at nanometer thickness,so they are expected to be used in ferroelectric memory.The HfO_(2)-based 1T1C memory has the advantages of fast reading and writing speed,more than reading and writing 1012 times,and high storage density,and it is the fast reading and writing speed that the only commercial ferroelectric memory possesses at present.The 1T ferroelectric field effect transistor memory has the advantages of non-destructive reading and high storage density.Theoretically,these memories can achieve the same storage density as flash memory,more than reading 1010 times,the fast reading/writing speed,low operating voltage,and low power consumption,simultaneously.Besides,ferroelectric negative capacitance transistor can obtain a subthreshold swing lower than 60 mV/dec,which greatly reduces the power consumption of integrated circuits and provides an excellent solution for further reducing the size of transistors.Ferroelectric tunnel junction has the advantages of small size and easy integration since the tunneling current can be largely adjusted through ferroelectric polarization switching.In addition,the HfO_(2)-based field effect transistors can be used to simulate biological synapses for applications in neural morphology calculations.Moreover,the HfO_(2)-based films also have broad application prospects in antiferroelectric energy storage,capacitor dielectric energy storage,memristor,piezoelectric,and pyroelectric devices,etc.Finally,the current challenges and future opportunities of the HfO_(2)-based thin films and devices are analyzed.