Development Of Wireless Multi-function Integrated Sensors Based On MEMS Technology

SAW(Surface Acoustic Wave) was first discovered by Lord Rayleigh, a physicist in UK, in 1885. Hereafter, SAW attractted much attention of researchers, and then it was applied to the fields of communication, radar, broadcast and TV. SAW sensor is an important branch of SAW technology. Its development began in the 1980s and SAW sensor has the characteristics of high accuracy, high sensitivity, low cost, low power loss, stable and smart and so on. It is easy to realize the parameter-measurement in many fields of physical, chemistry and biologic, therefore SAW sensor becomes more and more important in the sensor world.On the basis of SAW technology, a SAW temperature and gas sensor is designed in this thesis, including the design of IDT (interdigital transducer), the thin film as well as the frequency measurement system. Each parameter of IDT and the thin film material is selected carefully. The main contents are listed as follow:1) Introduction of the basis theory of SAW and the analytical model of SAW device.2) Introduction of the selection of Piezo-materical and comparison on the output voltages of IDT in which the substrate are the different crystals or the different cut of the same crystal.3) Developing a number of Parallel IDT arrays which constructed multi-channel SAW sensors for delay and resonance types by adopting 1/4 and 1/8 Wavelength interdigital splits, respectively.The center frequencies of the SAW sensors are selected as 99.85MHz and 174.5MHz respectively.4) Analysis particularly on the main physical properties of various films which adsorbed gases. The influence of the thickness of the films on the sensitivities of the sensors is derived theoretically, and the optimal thickness was obtained.5) The practical technical conditions and experiments are studied. In this section, analysis in detail is performed on the whole making technical project and key process such as anisotropic etching silica cup and plating film, especially on the anisotropic etching by using sputtered chrome as mask. Sensor chip was produced by advanced technology, and its working conditions and surface morphology are studied.A summary of the thesis and the views on future research of the designed sensor are given at last.