The Research Of PT/PZT/PT Micro-force Sensor

The study of micro electromechanical systems (MEMS) has shown significant opportunities for microsensors and microactuators based on piezoelectric films and silicon micromachining technology. The piezoelectric microforce sensors offer a lot of advantages for MEMS applications such as low energy loss, high sensibility, and easily integrated with piezoelectric microactuators. The microforce sensors based on the PZT, PT/PZT/PT piezoelectric thin films are regarded as the research objects in this thesis, the preparation and properties of the thin films are researched. And the simulation, fabrication and testing of the microforce sensors based on microcantilever structures are done.Static analysis, modal analysis and harmonic response analysis of the microcantilever structure with piezoelectric thin films are done using ANSYS10.0 software. It is obtained that the effects of the structure size of the microcantilever with piezoelectric thin films on the sensitivities of the microforce sensors under static state and dynamic state.The PT, PZT and PT/PZT/PT piezoelectric thin films are deposited by sol-gel method on Pt/Ti/SiO₂/Si substrates. The preparation technologies of the three kinds of piezoelectric thin films and the relations of the orientation and crystallization of PZT thin film and different PT seeding layer thickness are researched. It is obtained that the result of the 20 nanometer thickness PT seeding layer has an obvious effect on the orientation and crystallization of PZT thin film. The properties of the PZT and PT/PZT/PT thin films are compared under two kinds of annealing process. The PT/PZT/PT thin film has more complete crystallization than PZT thin film under the annealing process one; The PT/PZT/PT thin film also has more complete crystallization than PZT thin film under the annealing process two, and it has (100) preferred orientation, better dielectric property, but the leakage current is increased little.The two different microcantilevers with the PZT or PT/PZT/PT piezoelectric thin film are fabricated with bulk silicon technique of dry etching and wet etching and their elastic coefficients and sensitivities are measured. The sensitivities of the 1000μm×200μm×10μm size's microforce sensor with PZT, PT/PZT/PT piezoelectric thin films are 0.042mV/μm×N and 0.045mV/μN; the sensitivities of 500μm×100μm×10μm size's microforce sensor with PZT, PT/PZT/PT piezoelectric thin films are 0.004mV/μN and 0.007mV/μN. The microforce sensor with PT/PZT/PT piezoelectric thin film has more sensitivity than the microcantilever with PZT piezoelectric thin film when the microcantilever has the same size.