Characteristics of Thick Sol-Gel Lead Zirconate Titanate Films for Angular Rate Sensor Application
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Characteristics of Thick Sol-Gel Lead Zirconate Titanate Films for Angular Rate Sensor Application S. H. Lee1, T. Iijima1, K. Nakamura2, S. Tanaka2, M. Esashi2 1 Smart Structure Research Center, AIST, Tsukuba, Ibaraki 305-8568, Japan 2 Department of Mechatronics and Precision Engineering, Tohoku University, Sendai, Miyagi 980-8579, Japan ABSTRACT In this study, thick sol-gel PZT(Pb(Zr1-xTix)O3) films were fabricated and their characteristics were investigated for angular rate sensor applications. The crack-free thick sol-gel PZT films were successfully deposited on silicon substrates by multiple spin-coating technique combined with rapid thermal annealing(RTA). The thickness of the PZT films is 1.5
μm, which is required by a vibration angular rate sensor for a good actuation and sensing. The remnant polarization of the PZT films is 12.0μC/cm . The PZT films were applied to the vibration angular rate sensor structure, and the vibration of 1.78μm in amplitude at the resonant 2
frequency of 35.8kHz was obtained. In this case, the driving voltage of 5Vp-p by bulk piezoelectric materials was applied to the driving electrode with out of phase signal through voltage and inverting amplifier. The oscillating output voltage obtained by external actuation using a stacked piezo-actuator showed the values of 0.76V and 0.87V in outer/inner driving electrode at driving voltage of 5Vp-p. INTRODUCTION Development of reliable actuation and high sensitivity to vibration is one of many challenges in thin film MicroElectroMechanical Systems(MEMS) devices. Piezoelectric actuation using bulk ceramic materials is well known, but widespread use in MEMS requires suitable deposition and integration methods, which are compatible with large-scale manufacturing[1]. Micromachined vibration inertial sensors are very promising devices for many applications in such areas as automotive safety, consumer products, various industries, medicine and space. Conventional piezoelectric vibration angular rate sensors use bulk PZT material[2]. These sensors have a non-piezoelectric (usually metal) oscillating body on which PZT resonators are attached with adhesive. This structure, however, needs complicated B5.46.1
manufacturing techniques such as the bonding of the PZT resonators, and is not suitable to mass production. Also, these sensors have the severe drawback of the low thermal stability, because the large difference of thermal expansion coefficients between the metal oscillating body and the PZT resonators generates large thermal mechanical stress. Using PZT films as the resonators of vibration angular rate sensors is the promising way to overcome the above-mentioned drawback. Several methods such as sputtering, chemical vapor deposition(CVD) and sol-gel method have been used to deposit PZT films[3-5]. Among these methods, the sol-gel method has the advantages of easy control of chemical composition and low good piezoelectric property. A
μ
thick PZT film of more than 1 m in thickness often suffers from cracks and bad crystal orientation. In this p
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