Design and characterization of a buckling-resistant perforated MEMS membrane under residual stress

Abstract

Micro Electro Mechanical Systems (MEMS) membranes are utilized as both transmitter and receiver in acoustic and ultrasound applications. Their operating frequency ranges are determined by their resonance frequencies. Thus, the resonance frequency estimation is one of the most critical parts of the membrane design. In this study, two perforated circular MEMS membranes are designed, microfabricated and characterized to get proper operation under residual stress since this stress might cause buckling of the membrane. Finite element methods (FEM) are applied and optical measurements are taken to extract the resonance frequencies. For the fundamental mode, the FEM results deviate 5.5% and 6.7% from the experimental work. 33.4% stress relaxation is achieved for the proposed perforated membranes. Furthermore, eight different circular membranes are simulated and compared with the analytical solutions. The minimum and maximum average percentage errors are acquired as 0.5% and 3.3% for the fundamental mode. The electrical characterizations are carried out with the impedance analyzer and results are supported by FEM. Stress was successfully managed with the help of the perforation as verified by the experimental work and simulations.