Towards high fidelity high efficiency MEMS microspeakers

This paper presents simulations and microfabrication of different parts of high fidelity electrodynamic MEMS loudspeakers with high electroacoustic conversion efficiency. The originality of the structure lies on the use of rigid silicon membranes suspended by a whole set of silicon beams instead of flexible polymer membranes usually found in MEMS loudspeakers. The microspeaker structure includes a planar copper microcoil electroplated on the silicon membrane and permanent magnets bonded on the substrate. Microstructure of the silicon membrane was optimized using FEM simulations for providing both rigidity and lightness of the mobile part. The results presented on a deep RIE etched 15 mm diameter silicon membrane structured with 40 stiffening ribs and on a 30 µm thick microcoil with 35 turns experimentally show the feasibility of key stages required for manufacturing of MEMS microspeakers with outstanding properties.