用于器件级真空封装的MEMS加速度传感器的设计与制作
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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6.8 mm×5.6 mm×1.72 mm,其中,敏感质量块尺寸为3.2 mm×3.2 mm×0.86 mm,检测电容间隙2.1μm。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1.53V/gn,C-V特性正常,氦气细漏<1×10-9atm-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 1.53V/gn.The resonant frequency is 861 Hz and quality factor Q is 76.The fine leakage of He is lower than 1×10-9atm-cm3/s and has no bubbles during gross leakage test.
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 1.53V/gn.The resonant frequency is 861 Hz and quality factor Q is 76.The fine leakage of He is lower than 1×10-9atm-cm3/s and has no bubbles during gross leakage test.
引文
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[2]Levinzon F A.Fundamental noise limit of piezoelectric accelero-meter[J].IEEE Sensors Journal,2004,4(1):108-111.
[3]Gabrielson T B.Mechanical-thermal noise in micromachined a-coustic and vibration sensors[J].IEEE Transactions on Elec-tron Devices,1993,40(5):903-909.
[4]Shahriar R M,Chitteboyina M M,Butler D P,et al.Device-levelvacuum packaging for RF MEMS[J].Micro-Electro-MechanicalSystems,2010,19(4):911-918.
[5]李童杰,董景新,刘云峰.梳齿式微机械加速度计的研制[J].传感技术学报,2009,22(3):320-324.
[6]李伟.高gn值硅微加速度计的结构设计与分析[D].南京:南京理工大学,2005.
[7]Xiao F,Che L F,Xiong B,et al.A novel capacitive accelerometerwith an eight-beam-mass structure by self-stop anisotropic etchingof(1 0 0)silicon[J].Journal of Micromechanics and Microengi-neering,2008,18(7):1-7.
[8]徐玮鹤,林友玲,车录锋,等.一种圆片级硅三层键合的三明治加速度传感器[J].传感技术学报,2008,21(2):230-232.
[9]Qu H,Fang D,Xie H.A monolithic CMOS-MEMS 3-axis accele-rometer with a low-noise,low-power dual-chopper amplifier[J].IEEE Sensors Journal,2008,8(9):1511-1518.
[10]Jiang X.Capacitive position-sensing interface for micromachinedinertial sensors[D].Berkley,California:University of California,2003.
[11]戚玉婕,车录锋,孙腾,等.反馈补偿对高Q值加速度计动态性能的影响[J].半导体技术,2011,36(1):26-30.
[12]Bao M H.Analysis and design principles of MEMS devices[M].Shanghai:Fudan University Press,2005:135-136.
[13]Selvakumar A,Goldberg H D,Yu D,et al.Sensor design andprocess:US,274,079 B2[P].2000—09—21.
[14]毛健,车录锋,林友玲,等.一种电容间隙精确可控的高对称加速度传感器[J].固体电子学研究与进展,2009,29(1):143-146.
[15]尹颢,杨恒.驱动信号对电容式传感器特性的影响分析[J].传感技术学报,2000,13(3):168-173.
[16]李锦明,张文栋,李林.电容式微机械陀螺品质因子测试方法研究[J].中北大学学报,2006,27(4):357-360.