| Ferroelectric random access memory?FRAM?is realized by utilizing the remanent polarization bistable characteristics of ferroelectric materials.It has the characteristics of fast reading and writing speed,low power consumption and good radiation resistance.It has very important application potential in the fields of automotive electronics,aerospace and other fields where safety and reliability are particularly demanding.PZT ferroelectric thin film is irreplaceable in FRAM device ferroelectric thin film materials because of its large remanent polarization,good hysteresis loop squareness,low polarization reversal voltage and fast reversal speed.However,its poor fatigue resistance is a bottleneck that hinders its application.When PZT is integrated with the electrode material Pt,the fatigue phenomenon is prone to occur with the increase of the number of polarization inversions,which seriously affects the lifetime and reliability of the FRAM.In this paper,a BMN buffer layer was introduced between PZT ferroelectric thin film and Pt electrode to study the effect of buffer layer on ferroelectricity and fatigue performance of PZT ferroelectric thin film,and the temperature stability of PZT/BMN thin film was discussed.The main conclusions are as follows:1.The PZT thin film forms a pure perovskite structure under the heat treatment conditions of layer annealing and rapid annealing,with the heat treatment between 550-750oC for 30-300 s.After heat treatment at 700-750oC for 180-300 s,the grain growth is uniform but does not grow abnormally.The critical thickness of PZT film is 580 nm,which could be reduced to 470 nm by introducing BMN buffer layer with a thickness of 10 nm.2.The introduction of BMN buffer layer between PZT ferroelectric thin film and Pt electrode can effectively reduce the dielectric loss and leakage current of PZT thin film,and improve the anti-fatigue performance by improving the crystallization quality of PZT thin film and inhibiting the interdiffusion of PZT and Pt.The interdiffusion layer thickness of pure PZT film and Pt reaches 110 nm,and when the electric field strength is 100 kV/cm,the leakage current is 5.30×10-5 A/cm2,and the number of repeated reading and writing does not exceed 1010 times.After the introduction of the10 nm BMN buffer layer,the thickness of the interdiffusion layer of PZT and Pt is reduced to about 40 nm,and the leakage current is 4.4×10-6 A/cm2,which is reduced by an order of magnitude,and the number of reading and writing can be more than 1012times.3.Introducing the BMN buffer layer can effectively improve the temperature stability of the PZT film.On the one hand,the introduction of the BMN buffer layer can hinder the migration of defects,improve the crystal quality of the film,and reduce the leakage current,thereby increasing the dielectric temperature stability.On the other hand,the pinning effect of the BMN buffer layer on the domain wall of the ferroelectric thin film is gradually weakened with the increase of temperature,which can increase the remanent polarization value of the film and increase the ferroelectric temperature stability. |
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