Growth And Application Of PZT Thin Films

As the appearance of integrated ferroelectrics technology,which develop by combining ferroelectric thin films with micro-electronic technology.Preparation, structure,properties and applications of ferroelectric thin films has become very active researching in the field of new materials.Among this,Lead Zirconate Titanate Pb(Zr_x,Ti_1-x)O₃(PZT) ferroelectric thin films which has perovskite structure because of its excellent properties of ferroelectric,dielectric,piezoelectric,pyroelectric and compatible with semiconductor technology that it becomes widely applications in Micro-electromechanical system(MEMS).It can be used for various applications, such as piezoelectric actuators,random access memories,pyroelectric infrared detectors,and ultrasonic devices,since PZT-based devices can own advantages of wide working bandwidth,fast response,and high sensitivity.Along with the increasing demand of micro/nano mechanical devices and their integration into silicon-based devices,it is desirable that high quality PZT thin films can be grown on semiconductor substrate.In this paper,we described the growth of PZT spin-coating thin films on different substrates,included Si,Si₃N₄/Si,Ti/Siå'ŒPt/Ti/Si,by using Sol-gel method. The XRD method is employed to characterize the preferential orientation of PZT thin films,and then we have studied the influence of different treatment temperature on Pt/Ti/Si substrate on the orientation and crystalline quality of PZT thin film.The residual stresses of PZT thin films on the Ti and Pt/Ti layer are investigated as well. The results show that the residual stress of PZT films on the Pt/Ti layer is lower than that on the Ti layer,which indicates that the crystallization of PZT thin films on the Pt/Ti layer is better and thus the Pt/Ti composite layer is a good choice as the bottom electrode for practical MEMS and nano devices.The SEM and AFM are used to study the polycrystalline structures and morphologies of the thin films.Tested results show that the prepared PZT thin films on Ti and Pt/Ti layers exhibit well-developed crystal characteristics with the single perovskite phase and good surface morphology.The AFM micrographs of these PZT thin films show that the quality of thin films is significantly enhanced and the grain size increases after annealing.Then we used the MEMS techniques in Pen-Tung Sah MEMS Research Center of Xiamen University.We developed the process flow of measuring the electrical characteristics of PZT thin films by using the Sol-gel method and tested the electrical characteristics of PZT thin films.Measurement results show that the PZT film with single-layer heating treatment at 400℃and annealing treatment at 650℃on the Ti electrode,resulting in remanent polarization(P_r) of 8.6μC/cm² under an applied voltage of 3V.The PZT thin film with single-layer heating treatment at 400℃and annealing treatment at 650℃on the Pt/Ti electrode has remanent polarization of 11.0μC/cm²,owing to the preferential orientation of PZT(100).Based on these,PZT thin films prepared by using the sol-gel method in our study can be applied to developing PZT-based ferroelectric MEMS devices.Finish,we set up the equivalent circuit model of the mechanical structure of micro bulk acoustic wave resonator(BAWR).We use PSPICE software to obtain the resonator characteristics of the resonator.Aim at the various parts of resonator,we analyze the size parameters of resonator on the impact of frequency-based.