MEMS mirro modelling : literature review

The subject of the overall master thesis project is failure in resonant MEMS mirrors as used in for example pico projectors. Fracture is a realistic problem, because the MEMS is manufactured from silicon, which is a very brittle material. This problem should be taken into account as early as possible, i.e. during the design process, to create a robust and reliable product. The first step towards this is to gain insight in the fracture limit. This report presents an overview of all relevant literature information subdivided in three main categories: material, manufacturing and modeling. It forms the basis on which the master thesis project will continue. Firstly, chapter one provides the required information regarding possible applications and the design of the device. Furthermore, the problem of the overall master thesis project and goal of this literature review are presented in chapter one. The next chapter contains all relevant material properties for both silicon and silicon dioxide. These are the main materials used in the MEMS. Silicon is a well investigated material, because of its use in semiconductor industry. Elastic properties, crystal orientation, dislocation properties and fracture mechanisms are reported to complete this overview. Chapter three focuses on the manufacturing processes and describes their relevance with respect to fracture. Some processes, e.g. etching can introduce small defects in the geometry of the MEMS. These defects are important to consider when investigating fracture problems, because they typically introduce stress peaks which might lead to crack initiation or growth. Finally chapter four discusses three different modeling methods, i.e. cohesive zone model, virtual crack closure technique and j-integral. The latter method is most preferable, because it does not rely on the stress state in the singular crack tip. The report ends with a final overview of all relevant information as presented throughout the report.