Study On ⁶⁰Co γ Ray Total Dose Radiation Effect Of Fluorite-Type Zr-Doped Hafnium Oxide Ferroelectric Thin Film

Ferroelectric memory（Fe RAM）is a non-volatile memory that uses ferroelectric materials as data carriers.Because of its good radiation resistance,it has been receiving much attention in the medical,aerospace and other fields.However,the existing perovskite-type ferroelectric thin film materials have poor scacility and are not compatible with the complementary metal-oxide-semiconductor（CMOS）process,which makes the integration process of Fe RAM complicated and the storage capacity small,thereby limiting the large-scale application of Fe RAM.The fluorite-type hafnium oxide-based ferroelectric thin film（FE-Hf O₂）is a new type of ferroelectric material that is highly compatible with the CMOS process,and can maintain ferroelectricity even when the thickness is as thin as 3 nm or less.This brings a turning point for the development of high-density,radiation-resistant Fe RAM.However,there are few reports on the radiation effect of FE-Hf O₂.In addition,studies have shown that there are some differences in the radiation resistance of ferroelectric materials with different crystal structures.Based on this,this paper first prepared Zr-doped hafnium oxide（HZO）ferroelectric thin film with electrical properties more suitable for Fe RAM application;and systematically studied the total dose radiation effect of the prepared HZO ferroelectric thin film.The main research content and results include:（1）Based on the application requirements of Fe RAM,Ti N/HZO ferroelectric thin films/Ti N ferroelectric capacitors were prepared by atomic layer deposition（ALD）method.The electrical properties of HZO ferroelectric thin films under different key process conditions such as different Zr O₂:Hf O₂ratio,annealing conditions and thickness was analyzed in detail.The results show that the electrical properties of the HZO ferroelectric thin film with a thickness of 12 nm,an annealing condition of 550℃/1 min and a Zr O₂:Hf O₂ratio of 5:5 are relatively good:when the operating voltage is 3 V,the average remnant polarization value of this sample is as high as 10μC/cm²,the average coercive field is 1.2 MV/cm,the relative dielectric constant is 20,and the leakage current density is about 10^-5A/cm²,showing a relative advantage in high-density Fe RAM applications.（2）The effect of ⁶⁰Coγray ionizing radiation on the electrical properties and microstructure of HZO ferroelectric thin films was systematically studied.The results show that when the thickness of the HZO ferroelectric thin film is reduced from 20nm to 12 nm,the effect of ⁶⁰Coγray ionizing radiation on its electrical properties is also reduced,which shows the scalability of the radiation-resistant HZO-based Fe RAM.After exposure to a dose of up to 10 Mrad（Si）,the remnant polarization of the HZO ferroelectric thin film with a thickness of 12 nm only decreased by 5%,and the relative dielectric constant decreased by 0.04%;moreover,the surface morphology,local domain switch,leakage current characteristics,retention performance and fatigue resistance have not changed significantly,which indicates that the HZO ferroelectric thin film has higher stability under high radiation dose environment.