Printed MEMS membranes on silicon

We report a new method for additive fabrication of thin (125±15 nm thick) gold membranes on patterned silicon dioxide (SiO₂) substrates for acoustic MEMS. The deflection of these membranes, suspended over cavities in a SiO₂ dielectric layer atop a conducting electrode, can be used to produce sounds or monitor pressure. This process uses a novel technique of dissolving an underlying organic film using acetone to transfer membranes onto SiO₂ substrates. The process avoids fabrication of MEMS diaphragms via wet or deep reactiveion etching, which in turn removes the need for etch-stops and wafer bonding. Membranes up to 0.78 mm² in area are fabricated and their deflection is measured using optical interferometry. The membranes have a maximum deflection of about 150 nm across 28 μm diameter cavities. Young´s modulus of these films is shown to be 74±17 GPa, and their potential sound pressure generation at 15 V is calculated.