三明治电容式MEMS加速度计的器件级真空封装

Device-Level Vacuum Packaging for a Sandwich Capacitive MEMS Accelerometer

为了降低微电子机械系统(MEMS)加速度器件的热机械噪声,提高信噪比,使之能应用于石油勘探和地震监测中,对一种三明治式电容加速度传感器的器件级真空封装工艺进行了研究。这种器件级真空封装方法采用可编程高真空封装设备和MEMS工业中常用的材料、工艺,可适用于不同尺寸或布局的MEMS芯片。利用该封装方法,对一种采用自停止腐蚀工艺在中间质量块键合层上制作出2个对称"V"型槽的三明治式电容加速度计进行了真空封装,并对封装后的器件进行性能测试。结果表明,该加速度计在有吸气剂的情况下,品质因子(Q)可达到76,理论热机械噪声为0.026μg/槡Hz,腔体内部压强小于13 Pa,He气细漏检测漏率低于3×10-10Pa.m3/s,氟油粗漏无气泡,满足地震监测要求。

A device-level vacuum packaging process was studied to reduce mechanical-thermal noise and improve signal to noise ratio（S/N） of micro-electro-mechanical systems（MEMS） accelerometers,which were needed in oil exploration and earthquake detection.The procedure took advantage of processing steps and materials used throughout the MEMS industry while providing maximum flexibility for changes in die size and layout.Prototypes of an accelerometer with two grooves,which formed passages used to remove air from cavity within the accelerometer,were packaged using the presented package techniques.The combination of getter with the packaging process results in a stable quality factor of 76,with the pressure of less than 13 Pa in the cavity.The theoretical value of thermal-mechanical noise is 0.026 μg/Hz,helium leakage is lower than 3×10-10 Pa·m3/s and gross leakage has no bubble.And it can meet the earthquake monitoring requirements.