Reliability Investigation And Testing System Development Of MEMS Devices

At present, MEMS devices have a huge potentison to be widely used in many fields. Compared with other industries, its production is very limited. The bottleneck for mass production and application of MEMS devices is manufacturability, testability and reliability.For the diversity of MEMS devices and related material, and the complexity of manufacturing technology, it is impossible to characterize the properties of all MEMS devices in a dissertation. In this paper, two typical MEMS devices i.e. RF MEMS capacitive switch and capacitive MEMS pressure sensor were used for developing the techniques for investigation of reliability and testability of MEMS devices.Radio frequency (RF) microelectromechanical system (MEMS) capacitive switches has a promising prospect on applications for military and commercial telecommunication systems. However, despite these highly attractive advantages, there are still some unsolved problems, which currently prevent MEMS switches from successful integration into practical RF systems and commercial products. The main problem is dielectric charging effect, which will cause irreversible stiction of the switch movable part. In this project, a new theoretical model based on metal-insulator-semiconductor (MIS) structures was established for stiction modeling to investigate the charging and discharging mechanism within the dielectric of MEMS capacitive switches. Two technical schemes for reducing charge accumulation without changing the basic principle of the switch were proposed: (1) reducing charge injection and (2) increasing the speed of charge combination within the dielectrics. In experiments, three methods were conducted to reduce charge accumulation:①Designing the multi-magnitude wave for actuation voltage for injecting both negative and positive polarity charges to neutralize the injected charge;②Doping dielectric layer with donor or acceptor type impurity for creating recombination centers to speed up relaxation process of injected charge;③Depositing multi-layer dielectric layer for creating interface recombination mechanism to assist the vanishing process of the injected charge. The research work can provide theoretical background and practical techniques to improve the reliability of MEMS capacitive switches.As second part of this thesis, we presents a construction project which based on virtual instrumentation, data acquisition card and LabVIEW graphical programming language for the MEMS pressure sensor test system. Using computer as the control center, the test environment parameters, such as temperature, can be settled. Dynamic signal is obtained by the data acquisition card, handled by the data-processing module of LabVIEW toolkit, displayed and printed automatically. The system can realize multiple functions, such as signal acquisition, processing and presentation, and can be used as in house test tool.This paper mainly includes two kinds of typical MEMS devices and has made some progress. However challenges still hinder the development of MEMS, which requires continuous scientific research and technological exploration in future.