Simulation and fabrication of a MEMS optical scanner device considering deformation caused by internal stress

We fabricated a MEMS actuator device that is used as an actuator component of an optical scanning device without deflection of the device using finite element method (FEM) software. When Pt/Ti/PZT/Pt/Ti/SiO2 multilayers were deposited on a silicon-on-insulator (SOI) wafer in order to fabricate the MEMS actuator device, the wafer was deflected because of inner stress generated by thin-film deposition, and as a result, the MEMS actuator device using the deflected wafer was also deflected. We aimed to define the relationship between the deflection of the SOI wafer and the deflection of the MEMS actuator device by simulation. Moreover, by using this relationship, we determined the optimal deflection of the SOI wafer after the deposition of thin films, enabling the fabrication of a MEMS actuator device without deflection, by simulation. From the simulation result, when the changes in the deflection of SOI wafers were 14.1 and 7.4 μm, the displacements of the MEMS actuator device were 1.1 and 5.7 μm, respectively. The simulation results were in good agreement with the experimental results. From the simulation results, the optimal wafer deflection for preventing the deflection of the MEMS actuator device was 15.6 μm. This value was close to the experimental value, 14.1 μm. This method enables easy simulation of any MEMS device that is complicated in design and which uses multilayer thin films.