Microelectromechanical (MEMS) VLSI structures for hearing instruments

In this thesis two microelectromechanical (MEMS) structures have been designed for use in a hearing instrument. MEMS realization of a capacitive microphone has been designed that has a higher sensitivity in mV/Pa than the sensitivity of the existing MEMS microphones together with an extended audio frequency response range. The microphone is designed using a low residual stress polysilicon germanium diaphragm of thickness 0.8 mum and an area of 2.5 x 2.5 mm2, an airgap of thickness 3.0 mum and a silicon nitride backplate of thickness 1.0 mum with 1280 acoustical ports. Each acoustical port has a dimension of 30 x 30 mum2. The microphone is constructed using a combination of surface and bulk micromachining techniques in a single wafer process to achieve a sensitivity of 52 mV/Pa and a frequency response extending up to 18 kHz. The electromechanical analysis of the microphone structure is carried out using IntelliSuite MEMS software with an accuracy of convergence of 0.005 mum. (Abstract shortened by UMI.)...