一种低温制备的高灵敏度MEMS电容传声器

摘要

MEMS传声器是将声音信号转换成电信号的传感器.目前,MEMS传声器的研究主要涉及 MEMS电容传声器和MEMS压电传声器压阻传感器2种.与其它类型的MEMS传声器相比,MEMS电容传声器具有高灵敏度、高信噪比、频率响应平坦、低温度系数等突出的优点,被广泛使用在便携式设备、多媒体系统、助听器、信息采集等方面.设计和制备了一种高灵敏度的MEMS电容传声器,而且制备器件的工艺温度最高为300 ℃,可以兼容IC工艺.在本文,利用牺牲层的方法实现圆形振动薄膜,避免了方形薄膜存在的应力集中问题,并克服了干法制备圆形薄膜成本高的问题.基于聚酰亚胺材料,优化成膜工艺参数,实现低应力的圆形振动薄膜.通过设计防粘连结构,避免器件释放干燥过程中出现的薄膜粘连问题.根据振动膜应力为5 MPa,半径为2.5 mm,厚度为1 μm,电极半径为380 μm,间隙为1 μm的设计参数进行理论计算,该器件的电容在1 Pa 声压下的变化量为千分之一.与市场流通的MEMS传声器相比,高出约一个数量级,可被用于远场拾音,从信噪比极低的环境中拾取关键的声音信息.%MEMS Microphone is the sensor converting the sound signal into the electrical signal. At present,the re-searches of MEMS Microphone mainly refer to condenser microphone,piezoelectric microphone and piezoresistive microphone. Compared with the other MEMS microphone,MEMS condenser microphone possesses prominent advan-tages of high sensitivity,high signal to noise ratio( SNR) ,flat frequency response and low temperature coefficients, which is widely applied in portable device, multimedia equipment, hearing-aid, information acquisition. A MEMS condenser microphone with high sensitivity is designed and prepared at temperature of less than 300°C which is compatible with IC processing. The method of sacrificial layer is used to develop the circular vibrating membrane which avoids stress concentration question in quadrangular membrane, which overcomes expensive dry etching. Based on polyimide material and optimized processing parameters of membrane preparation,low stress circular mem-brane is developed. The question of film adhesion in release process is avoided by designing anti-adhesive structure. According to the theoretical computation,the capacitance change of the device with the stress in vibrating membrane of 5 MPa,the radius of 2.5mm,the thickness of 1um and the electrode radius is thousandth at 1 Pa sound pressure. Compared with MEMS microphone being sold,the above capacitance change is an order of magnitude larger than that. The MEMS condenser microphone in this paper can be applied in far-field pickup that picking important sound signal from low SNR circumstance.