MEMS Cantilevers Actuated By PNZST Antiferroelectric Film

Since the electrostrictive effect is caused by the electric field,the antiferroelectric films have the advantages of large strain,short response time,and large driving force,which can significantly improve the properties of MEMS actuators.Based on the properties of antiferroelectric films,a cantilever MEMS actuator based on(Pb_0.99Nb_0.02)[(Zr_0.85Sn_0.13Ti_0.02)]_0.98O₃(PNZST)antiferroelectric film is proposed in this paper.And,the constitutive relation of the actuator is analyzed theoretically.Then,the microstructure and energy storage properties of the antiferroelectric film on different bottom electrodes are analyzed by preparing PNZST antiferroelectric films.Lastly,combined with MEMS processing technology,the MEMS Cantilevers actuated by PNZST antiferroelectric film is fabricated,and its properties are tested.The actual production process is to sputter LaNiO₃(LNO)bottom electrode on silicon substrate by RF magnetron sputtering.Then,the PNZST antiferroelectric thin films were prepared on the LNO/Si and Pt/Ti/SiO₂/Si substrates by the sol-gel method.The results of X-ray diffraction(XRD)indicated that the orientation of(001)/(100)diffraction peaks were observed in both films.However,the splitting of(002)/(200)peak is not significant in both films,which indicates that the ferroelectric rhombic phase(F_R(LT))may exist in the films.Atomic force microscopy(AFM)results show that the average roughness and grain size of PNZST/LNO film are about 3nm and52nm,and PNZST/Pt are 2.5nm and 51.8nm,respectively.The surfaces of the films are relatively smooth and the grain sizes are average.The influence of the bottom electrode on the surface morphology of the film can be ignored.The ferroelectric test shows that the ferroelectric loop of antiferroelectric films on LNO substrate is closer to the antiferroelectric phase,while PNZST/Pt is close to the ferroelectric phase.Then the effects of two substrates on the dielectric properties and energy storage properties of PNZST films are analyzed.The MEMS Cantilevers actuated by PNZST antiferroelectric film was fabricated by MEMS device integrated manufacturing process.The frequency response properties of the actuator were tested and analyzed by the equipment.The test results show that the resonance frequency is 21.38kHz and the vibration mode is good when the beam length and width are 750mm and 200mm.According to the theoretical analysis,the young's modulus of antiferroelectric cantilever MEMS actuator is 33.7GPa.The quality factor Q is 667,indicating that the energy loss is small.The measurement of driving voltage and tip displacement shows that the tip displacement increases nonlinearly with the driving voltage before the phase transition at the resonance frequency,and hardly changes with the driving voltage after the phase transition.At this time,the tip displacement remains about 0.91mm,and the displacement of each point in the profile increases with the length and AC voltage.At low frequency,the tip displacement and rate of change decrease obviously,which indicates that the linearity of tip displacement is good at low frequency.