The Research On Perparation Process On Si-Substrate Flexural Plate Wave Sensors

With the increasing emphasis on environmental protection, more and more peoplebegin to pay attention to the air quality. In the various inspecting methods, MEMS FPWsensor has attracted much attention. The sensitivities of FPW sensor increase with thedecrease of film thickness. FPW sensors are fabricated with MEMS micromachiningtechnique, which can reduce the film thickness and improve the sensitivity. This researchwork has the important researching value.Si-substrate FPW sensor structure is properly optimized with the theoretical analysismethod. The layout size of interdigitated electrode and the multilayered compositemembrane structure are in detail designed. The properties of different thin films and theeffect of material parameters on sensor performance are in-depth investigated fromtheoretical aspect. Two pairs of interdigital electrodes are designed on the multilayercomposite board respectively, being the A0 mode Lamb wave excitation electrode andreceived electrode. The layout sizes of the interdigital electrode are determined. DC andRF magnetron sputtering are applied to deposit the ZnO films, respectively. The crystalstructures are investigated with XRD and SEM. The electricity performance is indirectlyanalyzed with the fabricated high-harmonic bulk acoustic resonator (HBAR). The stressis analyzed with the fabricated multilayer composite membrane. AlN piezoelectric thinfilms are also prepared with the RF magnetron sputtering. Then, the impacts of sputteringpressures and different gas ratio on preferred orientation of AIN films are analyzed.Finally , the MEMS FPW device based on the ZnO film is fabricated with the DCmagnetron sputtering. And ZnO film prepared with the RF magnetron sputtering isapplied for the MEMS Lamb device. The frequency responses of MEMS FPW deviceand MEMS Lamb wave device are measured with the network analyzer. The responsefrequency is calculated, and the measured results are compared, which show that theapproximate theoretical analysis can be applied to measure the response frequency ofFPW devices.