Modeling of diaphragms for micromachined condenser microphones

We present and compare the different kinds of diaphragms for micromachined condenser microphones. The aim is to develop the microphones with high sensitivity. For micromachining diaphragm, there is significant internal (residual) stress, which strongly decreases the mechanical sensitivity of diaphragm. An analysis was performed using the MATLAB software. According to our calculations, a corrugated diaphragm can greatly increase the mechanical sensitivity of the microphone diaphragms due to the reduction of the initial stress effect without changing the process conditions. A planar diaphragm is more rigid than a corrugated diaphragm at either small and large deflections (or pressures) when both diaphragms have same level of initial stress. Flat diaphragms show a nonlinear relation between the deflection and the applied pressure. The nonlinearity is caused by stress due to stretching of the diaphragm. It has been shown that corrugated diaphragms have a larger linear range than flat diaphragms, because of the achieved reduction of the initial stress in the diaphragm.