Design of Monolithic Electret Condenser Microphone

• Main Authors: Shi San Wang, 王世賢
• Other Authors: Hong Chin Lin
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/42744674471469166223

碩士 === 國立中興大學 === 電機工程學系 === 93 === Recently, more and more researchers have studied silicon - micromachined capacitive microphones due to their superior performance, such as, high sensitivities, low noise, flat frequency response in wide bandwidth, high stability and reliability. A pure condenser microphone requires an high external bias for operation. However, an electret microphone does not, since it has an internal built-in bias. Therefore, the electret microphone only needs a low supply voltage for sense circuits, including a preamplifier, an operational amplifier. In this thesis, new structures of electret condenser microphones are proposed. The bottom electrode of microphone and the electret is being or was fabricated by National Nano Device Laboratories (NDL) and Chip Implementation Center (CIC). After that, fabrication of the diaphragm of microphone will be performed in our lab. The method to inject charge into the 1×1mm² electret is using FN tunning. Note that the arsenic doping concentration of electret is as high as possible to improve the charge distribution. In order to store the charge in the electret as much as possible, various charge injection methods were also investigated.