Research On High Performance And High Reliability RF MEMS Device Baced On Flexible Substrate

The 21 st century is the era of informatization.With the rapid development of the communication industry and the continuous improvement of communication methods,electronic devices in the field of radio frequency and microwave have received much attention.RF MEMS(radio frequency microelectromechanical system)electronic devices have been widely used in information,national defense,medical treatment and other aspects due to their high linearity,low loss and small size.As the increasingly complex application space and application environment in airborne,satellite-borne radar and Internet of Things communication systems,RF MEMS devices based on flexible substrates have become research hotspots in recent years due to their small size and flexibility.At present,the main research content is around device design,preparation,and device performance research and testing under non-bending.There is little theoretical analysis and experimental verification of device performance drift under bending conditions,and even less prematching design under bending conditions to optimize device performance under bending conditions.However,combined with scientific research and engineering application of actual demand,the establishment of a typical flexible RF MEMS devices for the substrate bending response theory model,the preliminary matching to the device designed to eliminate the effects of substrate bending,according to the theoretical model for the simulation and experimental verification work to promote the research and application of flexible RF MEMS devices is of great significance.Based on the typical RF MEMS devices with flexible substrates,The bending characteristics model of the device under different bending conditions was established in the thesis.The influence of substrate bending on the mechanical properties,microwave performance and dynamic characteristics of typical RF MEMS devices in complex environments was studied in this thesis.After analyzing and summarizing the development process and application scenarios of flexible RF MEMS devices,the following work was carried out:(1)Build 2D and 3D models of typical RF MEMS devices based on flexible substrates.According to the working principle of different typical devices,the mechanical properties,microwave performance and dynamic characteristics models of the electrostatically driven switch after bending and the capacitance change model of the four-terminal fixed capacitor under different bending conditions are established.The main parameters were extracted and analyzed,and the mechanical /microwave pre-matching design scheme of the RF MEMS switch under bending was proposed.(2)According to the typical RF MEMS bending theory model based on flexible substrate,combined with the LCP process limitations,the structure and size of several typical RF MEMS devices were determined,including double-ended fixed beam switch,cantilever beam switch,filter,capacitor and other RF MEMS devices.Then the mechanical properties and microwave performance of typical RF MEMS devices under different bending conditions are simulated.The simulation results are in good agreement with the calculated values of the theoretical model.(3)Design and prepare the layout of the typical RF MEMS device,test the performance parameters of the sample under different bending conditions.The results show that the mechanical properties,microwave properties and dynamic properties of the switch with the substrate bending are consistent with the theoretical model,and the matching structure significantly improves the microwave performance of the switch with the substrate bending under the bending condition.The filter length of the filter structure is different and the substrate bending performance changes are consistent with the simulation results.A typical RF MEMS device bending characteristic model is established in this thesis.For the first time,a three-dimensional bending theoretical model of a four-terminal fixed capacitor under different bending conditions is proposed.A pre-matching structure under bending conditions is designed to eliminate the effect of substrate bending on the device.The bending characteristics of typical RF MEMS devices are simulated,designed,fabricated and verified by experiments.