| Lead zirconate titanate(PZT) materials with excellent piezoelectric, ferroelectric and dielectric properties are widely used in the control part of the memory devices, sensors, drivers, and various precision instruments. PZT thin film electrical properties and crystal structure has a close relationship, prepared films with good crystallization is a guarantee of excellent electrical properties. Due to many factors affecting the properties in the film preparation process, and the crystallization mechanism of thin film growth is unclear; master the crystallization mechanism and film microstructure control growth is still the focus of the research. The most hope of researchers is mastering the growth characteristics of the film, and finding the optimized process conditions for controlling the orientation growth of the films.(111) oriented PZT thin film has excellent ferroelectric properties,it is an important material for preparation of ferroelectric random access memory(FRAM).In this paper, nucleation theory, interface energy and grain boundary diffusion theory were used to study the crystallization mechanism of PZT thin films, the effect of film microstructure on ferroelectric properties is discussed. Infrared rapid crystallization of PZT thin films, segmented fast annealing, and plasma assisted microwave annealing process for radio frequency(RF) magnetron sputtering respectively were studied.In this paper, the(Zr0.52Ti0.48O3) thin film with 200 ~ 300 nm thickness is sputtered on /Ti/SiO2/Si(111) Pt(100) substrates by RF magnetron sputtering. The effects of sputtering power, sputtering pressure and sputtering substrate temperature on the crystallization of PZT thin films were studied. The infrared rapid annealing process of the PZT thin films was adopted and the interface and grain boundary diffusion theory were used to study the relationship between the crystallization parameters and PZT thin films with preferred orientation growth. It is found that changing the crystallization temperature, heating rate and holding time can obtain the(111) preferential orientation film, and optimizing process parameters have been found, The relationship chart of the influence of orientation(111) orientation on the ferroelectric properties was drawn.The influence of PZT film thickness and grain size on the crystalline orientation and ferroelectric properties of the films were studied... It is found that the thickness of the film is determined by the lattice matching degree of the interface layer, the number of nucleation agent in the interface layer, and the grain boundary diffusion rate. After the thickness increases, the minimum principle of the interface determines the crystallization orientation. The more obvious the self polarization of the thin film is, the more the remnant polarization is. The grain size of the grain size is close to the domain wall, which is not good for the growth of the domain. That caused the small remnant polarization value.By studying the effect of substrate interface layer on the nucleation and preferential orientation of PZT film, The idea that the Pt and the surplus Pb can easily form PbxPt cluster molecules at high temperature are presented., The structure of PbxPt clusters is optimized by the software of Gauss at the level of TPSS/def2-TZVP., It is found that the molecules of the interface layer belong to the quantum dot category and the structure is similar to the PZT film(111) crystal plane., which can reduce the nuclear power of the orientation of the film(111) crystal plane. The effects of three substances PbO, PbxPt and Ti on the interface energy were studied., It is considered that(110) the crystal plane has the smallest interface energy, and the impurities at high temperature are easy to precipitate at the grain boundary of(100)(110) crystal grain. Control of the formation and diffusion of these substances on the interface layer can control the orientation growth of PZT film(111).By analyzing the experimental data, it is pointed out that the crystallization of PZT thin film in different growth periods were balance model or the grain boundary diffusion model. The preferential orientation of the thin film can be controlled by controlling the interfacial energy and the grain boundary diffusion rate at different growth modes.Based on the analysis of the PZT film growth mode, the fast crystallization and second crystallization process of the PZT film were designed. When the temperature was higher than 650℃, the nucleating agent PbxPt form and the(111) orientation nucleation density increase. It is good for the thin film grain to grow up uniformly when reduce the crystallization temperature and prolonging the holding time. The nucleation phase and grain boundary diffusion of the film crystallization process were controlled respectively, and the(111) oriented PZT film can be obtained. The growth mode of PZT film was verified.In order to reduce the crystallization temperature and solve the problems under high temperature, such as PbO volatile of the thin film, a higher residual stress and so on, the crystallization process of the plasma assisted microwave annealing is applied to the crystallization of PZT thin film. The influence of microwave crystallization process on the crystallization and ferroelectric properties of the films was studied. The optimal crystallization process of microwave power 800 W and crystallization for 5 min was obtained and the PZT films were well crystallized in this condition, Pr=38μC/cm2,Ec=170kv/cm. At the same time, the microwave crystallization mechanism of PZT film is preliminarily discussed. In the initial stage of crystallization, oxygen plasma is the main source of energy. At low temperature(450℃), pyrochlore phase form, With the increase of the temperature, the microwave absorption enhancement, the microwave thermal effect is gradually obvious. The temperature is too high will lead to the dissolution of atomic diffusion reaction; the key factor of obtaining the preferential orientation film is the microwave power and the crystallization time. |
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