Based On Mems Optical Modulator Design And Process

The development of MEMS(Micro-electro-mechanical system) technology brings up brand-new methods in designing and fabricating optical devices. Many novel MOEMS(Micro-opto-electro-mechanical system) devices are presented in recent years. However, the traditional thin film technology is not compatible with MEMS fabrication. Most of MOEMS devices are constructed on Silicon substrate by semiconductor technology. These devices are commonly used in infrared wave band because of the transmission character of Silicon, which limits the application of devices on visible wave band especial display field.In chapter 2, the typical micromachining technology for MOEMS device is studied and two kinds of micro optical modulators are designed by MEMS technology, especially thin film technology. These devices are fabricated on K9 glass substrate and based on principium of electrostatic tunable F-P cavity. The characteristics of basic structure of these devices are analyzed theoretically. A self-consistent method is introduced to solve the coupling problem between the electrostatic force and the structure. Using this method, FEA(Finite Element Analysis) software Ansys is aided to calculate the deformation of the membrane at various voltages applied. The electromechanical performance is analyzed and simulated using finite element analysis method.In chapter 4, three kinds of fabrication processes are mentioned and compared according to the designed structure. Both advantage and disadvantage of these processes are analyzed. The film technologies involved in these processes are practised. The relationship of SiNx and SiOxNy thin film's refractive index, extinction coefficient and composition with coating conditions is studied. As a result, SiNx thin film with high refractive index and low extinction coefficent can be fabricated by keeping the total pressure at 0.5 Pa and the flow rate N2-to-Ar at 3:14. While SiOxNy thin film's refractive index can be controlled from 1.92 to 1.46 by adjusting the gas flow, and the optical gap calculated using Wemple DiDomenico single-oscillatormodel lies between 5eV~6.5eV.During the process of releasing sacrificial layer, the stiction effect and buckling effect are studied. Stiction effect is caused by capillary force during liquid-gas phase transition while buckling effect relates to the film stress. We do solve stiction effect by modifying the membrance's structure and using isopropyl alcohol. In the analysis of buckling effect a new method is applied in the determination of film stress. With MEMS structure, film stress can be measured precisely at real time.Through the work presented in this thesis, we achieve many advances both at theory and practice. At last, the conclusion and advice for future work are made.