Design And Fabrication Of Micromirror Arrays

Micromirrors array, which is one of the most important devices in the Micro-Optical-Electro-Mechanical-system field, can be widely used in various macro optical areas, such as scanner, spatial modulator, etc. What is more, many functional systems which seem to be impossible have been realized by using micromirrors array, including image project display, adaptive optics, optical beam scanning system, etc. With the development of microfabrication technology, micromirrors array is developed with high frequency, large deflection angle, low driving power and large-scale array. The research presented in this thesis concentrates on the design, model and fabrication process of electrostatically actuated micromachined micromirrors array for the optical scanning system. In this thesis, the emphasis is placed on the following four parts.(1) The mechanism and structural characteristics of micromirror are analyzed systematically and the dimensions are given by combining the structural design principles and labortary conditions. A complete surface micromaching process is put forward to fabricate the micromirror and correspondent resist masks have been designed by LEDIT for fabrication processes.(2) The simulation with finite element analysis software ANSYS is presented in which the static and dynamical characteriastics of micromirrors array in the electro-mechanical coupling field are analyzed, such as stress, modal, transient respondence, etc.(3) The micro-fabrication processes are studied specifically, especially the double layer wiring and sacriface layer processes. Metal lift-off, PECVD SiO2 as interlayer dielectrics and reactive ion etching of SiO2 are researched for double layer wiring. What is more, the characteristics of ZKPI are analyzed, and then, vertical trenches on sacrifice layer are achieved by the wet etching method which has been optimized. Eventually, the sacrifice layer with designed hight, flat surface, stable chemical and mechanical performance is acquired by adjusting multi-coating and phased anneal. Additionaly, the optimal conditions to release the sacriface layer with O2 plasma is also studied in this thesis. (4) The process of forming posts of 12×10μm2 which serve as the electricity interconnection and the structual support by using electroless deposition of nickle on the aluminium layer is improved by optimizing the pretreatment.