Actuation force analysis and design optimization of microshutter array by numerical simulation method

Abstract

Next Generation Microshutter Array (NGMSA) is an electrostatically operated micro electro-mechanical system (MEMS) device for programmable spatial light filtering application. Original microshutter array (MSA), which is magnetically operated, was developed for the James Webb Space Telescope (JWST) NIRSpec multi-object spectrometer, and NGMSA inherited its design from the original MSA. Even though there has been incremental design changes in order to achieve stable electrostatic actuation, NGMSA operation still requires further study. Previous simulation efforts to model NGMSA’s actuation mechanics allowed to gain only general understanding of the behavior due to inadequate simulation and experimental methods. In this study, a novel electrostatic numerical simulation model is presented using COMSOL Multiphysics to accurately predict microshutter’s motion during actuation. The new model addresses all the issues that hinder realistic modeling. Current Microshutter Array yield and operation performance issues related to fabrication process are analyzed with this numerical model and a potential optimized design is proposed. The result shows that a few μm shorter shutter blade allows stable electrostatic actuation as well as better tolerance to the fabrication accuracy. Also, modified blade side shape reduces undesirable asymmetrical motions which cause failed stuck shutters.