Research On Ferroelectricity And Reliability Of Ferroelectric Hf_0.5Zr_0.5O₂ Capacitors

Traditional ferroelectric materials are currently hindered in the process of industrialization development due to their incompatibility with advanced CMOS processes,significant size effects and large depolarization fields.As a new type of hafnium oxide-based ferroelectric material was discovered in recent years,the ferroelectric Hf_xZr_1-xO₂(HZO)film has the advantages of high remanent polarization,small depolarization field,low annealing temperature,and compatibility with CMOS technology.It satisfies the increasingly for miniaturized and integrated ferroelectric devices.Ferroelectric HZO capacitors have fast polarization reversal characteristics and can be used in fields such as information storage,new computing architectures and new ferroelectric devices,but the reliability and stability of the devices have always been issues that cannot be ignored in practical applications.Based on the above requirements,the main work of this article includes the following:First,Magnetron sputtering is used to deposit low-resistance titanium nitride(Ti N)film as electrode,and atomic layer deposition is used to deposit HZO film as ferroelectric layer.Ferroelectric HZO capacitors are prepared by photolithography and rapid thermal annealing.Second,the ferroelectricity of ferroelectric HZO capacitors is characterized,and the hysteresis loop,PUND(Positive-Up-Negative-Down)curve,current loop,and C-V(Capacitance-Voltage)characteristic curve are tested.We study effects of the ratio of Hf and Zr,the thickness of HZO and the annealing temperature on the ferroelectricity of ferroelectric HZO capacitors.The results show that as the proportion of Zr doping increases,the hysteresis loop gradually changes from ferroelectric to antiferroelectric due to the increase of tetragonal phase ratio of HZO and relative permittivity.The remanent polarization of ferroelectric Hf_0.5Zr_0.5O₂capacitors is similar when annealing at 400??500?for 1 min.As the thickness of Hf_0.5Zr_0.5O₂increases,the concentration of oxygen vacancies decreases and so as the coercive field.Last,We performed reliability study of ferroelectric Hf_0.5Zr_0.5O₂capacitors,including fatigue characteristics,temperature stability and retention,and studied its failure conditions and failure mechanisms.The results show that the fatigue characteristics of ferroelectric Hf_0.5Zr_0.5O₂capacitors are improved with the increase of the thickness of Hf_0.5Zr_0.5O₂,up to10⁷cycles under an electric field of±2.5 MV/cm.As the temperature increases,the hysteresis loop has a positive drift due to the thermal imprint effect.In the retention test,the polarization retention ratio of the ferroelectric Hf_0.5Zr_0.5O₂capacitors was 93%after 10000 s at room temperature,and only 13.9%after 10000 s at 398 K.Electrical imprinting effect and thermal imprint effect cause the coercive field to drift positively,resulting in the decrease of remanent polarization within the same voltage range.