用于器件级真空封装的MEMS加速度传感器的设计与制作

摘要

设计了一种可用于器件级真空封装的三明治电容式MEMS加速度传感器.该传感器被设计为四层硅结构,其中上下两层为固定电极,中间两层为硅-硅直接键合的双面梁-质量块结构的可动电极.利用自停止腐蚀工艺在中间质量块键合层上腐蚀出2个深入腔内的V型抽气槽,使得MEMS器件在后续的封装中能够实现内部真空.为防止V型抽气槽在划片中被水或硅渣堵塞,采用双面划片工艺.划片后,器件的总尺寸为6.8mm ×5.6mm ×1.72 mm,其中,敏感质量块尺寸为3.2mm×3.2mm ×0.86mm,检测电容间隙2.1 μm.对器件级真空封装后的MEMS加速度传感器进行了初步测试,结果表明:制作的传感器的谐振频率为861 Hz,品质因数Q为76,灵敏度为1.53 V/gn,C-V特性正常,氦气细漏＜1×10-9 atm-cm3/s,粗漏无气泡.%A sandwich type of capacitive MEMS acceleration sensor used for device-level vacuum packaging is designed. The sensor is made of four-layer silicon wafers bonded together while the top and bottom wafers are the fixed electrodes and the cantilever-mass structure is made on the middle two wafers. Two grooves are etched in the middle mass block bonding layer by self-stopped etching process and used to remove air from cavity within the acceleration sensor, creating vacuum environment in subsequent packaging. A double-sided dicing process is developed to protect V-shaped grooves from water or silicon scrap. The total size of the sensor is 6.8 mm ×5.6 mm × 1. 72 mm and the size of mass is 3.2 mm ×3. 2 mm ×0. 86 mm. The interval of detecting capacitor is 2.1 μm. The performance of the device-level vacuum packaged sensor is tested. The C-V plot is normal and the sensitivity is about 1.53 V/gn. The resonant frequency is 861 Hz and quality factor Q is 76. The fine leakage of He is lower than 1 ×10-9 atm-cm3/s and has no bubbles during gross leakage test.