Rectangular polysilicon diaphragms: fabrication and characterization

Rectangular air-gap diaphragms are difficult to mechanically characterize. A standard fabrication process developed utilizing the smallest efficient etching access ports relative the diaphragm sizes, which ranged from 1406 μm² to 36864 μm². Polysilicon diaphragms having a thickness of 1 μm above a 1 μm air gap were fabricated on a silicon substrate and mechanically tested to determine the amount of force relative to geometry and size required to achieve maximum deflection and initial membrane sag using a standard Berkovich tip. The results showed that the force, maximum displacement, and unloading force curve fits followed power law distributions.