Ribbing of micro-plates as a remedy for stiffening and curling resulting during fabrication

The reliability of MEMS devices is significantly harmed by residual stresses arising from fabrication. These stresses usually yield to the stiffening and/or curling of the micro-plate. Previous literature shows that it is challenging to reduce both phenomena simultaneously. This paper proposes ribbing of the micro-plate as a remedy. A simple model for a fixed-fixed beam is first presented. The analytical solution of the beam model depicts that stiffening can be controlled by controlling the ratio between the cross-sectional area and the area moment of inertia. A non-linear finite element 3D model is developed. Results show that ribbed micro-plates are superior to conventional flat ones in many aspects. Stiffening and curling are both reduced by about 50 % and 64 %, respectively. The fundamental natural frequency is increased by 34 %. It is predicted that ribbing can improve the reliability of MEMS devices including pressure sensors, resonators, micro-mirrors, and switches.