Nowadays capacitive MEMS microphones are state of the art for mobile phones. Requirements for the microphones are a narrow sensitivity distribution, a high signal to noise ratio and a small microphone package. To fulfill these requirements a capacitive programmable MEMS microphone was developed. For this purpose a differential sensor chip and a programmable ASIC chip were combined into a microphone package. The new flip-chip package (3,35 x 2,5 x 1,0 mm3) has a large backvolume of 3,4 mm3 which allows a high signal to noise ratio of 65 dB(A) at a sensitivity of -38 dBV/Pa. The accuracy of the sensitivities is limited by fabrication tolerances of the MEMS microphones. Sensitivity tolerances below ±1 dBV/Pa were reached by adjusting the bias supply voltage and the gain. The standard deviation of sensitivity was reduced to values below 0,1 dBV. Further the signal to noise ratio was improved and the total harmonic distortion at high sound pressures was reduced by programming. The signal to noise ratio was improved by 1 dB(A). The total harmonic distrotions for sound pressures of 110 dBSPL were reduced from 0,8 % to 0,5 %. For this work lumped-element simulation models and a programming and measurement setup were developed. The measurement setup is based on a pressure chamber principle and allows programming and measuring the microphones. The measurement setup could be used in the laboratory as well as for production.    «

Nowadays capacitive MEMS microphones are state of the art for mobile phones. Requirements for the microphones are a narrow sensitivity distribution, a high signal to noise ratio and a small microphone package. To fulfill these requirements a capacitive programmable MEMS microphone was developed. For this purpose a differential sensor chip and a programmable ASIC chip were combined into a microphone package. The new flip-chip package (3,35 x 2,5 x 1,0 mm3) has a large backvolume of 3,4 mm3 which...    »