Study On The Polarization Stability Of Hafnium Oxide-based Ferroelectric Thin Films

The hafnium oxide-based ferroelectric field effect transistor(Fe FET)type memory is a strong competitor in the next-generation non-volatile memory,and has the advantages of low power,high speed,high capacity,and compatibility with CMOS processes.At present,on the basis of extensive research on the preparation,device structure,process and performance of thin films in Fe FET,researchers at home and abroad have launched small-capacity Fe FET principle chips.However,in the process of industrialization,the reliability research of new hafnium oxide-based ferroelectric thin films and devices is far from enough.This paper takes a new type of hafnium oxide-based ferroelectric capacitor MFM structure as the research object,and conducts an in-depth study on the effects of annealing temperature,annealing method,application temperature and electrical stress on its ferroelectric performance.The main contents are as follows:1. The effects of thickness,capacitor area,and application temperature on the performance of HZO ferroelectric thin films were studied.The test results of HZO ferroelectric thin film in the thickness range of 5-20 nm show that its ferroelectric performance depends heavily on the film growth process;through the capacitance area comparison experiment,it is found that the residual polarization and rectangularity are easily affected by the electrode area,more than 100?m×100?m area The residual polarization intensity becomes smaller and the squareness becomes worse.The test results under different application temperature environments show that the electrical performance of HZO ferroelectric capacitors does not change significantly at 85?,and the polarization stability is good.2. The effect of the integration process temperature on the performance of the ferroelectric thin film was simulated by different annealing methods,and it was found that the integration temperature at the back end would cause P_rattenuation and E_cdrift.Step annealing is more conducive to promoting thin film crystallization than single step high temperature annealing,and can reduce the"wake-up"effect to a certain extent,which provides a new idea for preparing hafnium oxide-based ferroelectric thin films without wake-up effect.3. Finally,a study on the effect of electrical stress on the polarization stability of ferroelectric thin films was carried out.Ferroelectric layer breakdown comes from time-dependent dielectric breakdown(TDDB),not stress-induced leakage current(SILC).The breakdown time is related to the electrode area,and the breakdown is related to the charge accumulation,and the breakdown voltage satisfies the Weibull distribution.The extrapolated service life of films with different thickness can reach more than 10 years.The effect of constant voltage stress(CVS)on ferroelectric performance is due to the directional rearrangement of defect dipoles,oxygen vacancies,and charged impurities after CVS,causing them to gather at the interface/grain boundary,resulting in domain pinning.The residual polarization value is reduced,and direct evidence is obtained in the experiment,which further explains the internal mechanism of the"wake-up"effect and provides a basis for device optimization.