Preparation Of AlN Piezoelectric Thin Films And A Hinged Micromachined Piezoresistive High-g Accelerometer

With the development of Science and Technology, inertial sensors are employed in industry much more widely, such as accelerometers for airbag crash systems and gyroscope for navigation systems in automotive industry. Inertial sensors fused by microelectronics and micromachining technology have shown vast vitality compared to conventional sensors technology. In this thesis, two sections are involved. One is the advance research of preparation of AlN thin films for Surface-Acoustic-Wave (SAW) gyroscope, and the other is focused on a hinged accelerometer, including design, fabrication, packaging and testing.In the first two chapters, the preparation of AlN thin films is studied. In Chapter 1, the motivation of research on SAW gyro and the progress of AlN thin films preparation and their application are addressed.In Chapter 2, the principles of DC reactive magnetron sputtering and SAW are introduced first. Then, to fit the requirements of thin films for SAW devices, preferred orientation and surface morphology of AlN thin flims are investigated by orthogonal design. The sputtering parameters, such as the sputtering pressure, the substrate temperature, and the nitrogen concentration, are discussed for their effects on thin films properties. Also expectation optimal conditions are carried out statistically, and this results will benefit for the application on SAW devices especially SAW gyroscope.In the last four chapters, a hinged silicon micromachined High-g accelerometer is discussed. This structure could increase the nature frequency significantly while maintaining a high sensitivity so that it could reproduce the input shock signal accurately. In this section, the design, fabrication, packaging and testing of devices are investigated. In Chapter 4, the device mechanism and mechanical models are described. FEM simulation is also used to verify and compare with simplified model and optimized model. Two optimized structures are concluded with sensitivity of 0.9, 1.2μV/5V/g and nature frequency of 577KHz, 494KHz respectively under 20000g range.In Chapter 5, two optimized accelerometer were fabricated, which demonstrated a high ability to control the process.In the last chapter, appropriate materials are chosen for the requirements of packaging. Then static and dynamic testings are introduced briefly.