基于硅硅键合技术的高精度压力传感器的研究

硅压阻压力传感器核心部件一般是由单晶硅和玻璃组成的微结构,由于单晶硅和玻璃的材料特性存在差异,在制造过程中会引入封装应力对传感器的性能产生不利影响。采用硅硅键合技术制造压力传感器核心部件的微结构,以同质材料替代异质材料实现器件的封装,可有效减少封装应力,提升压力传感器的性能。文中通过结合硅压阻压力敏感芯片的制造工艺和硅硅键合工艺,实现了敏感芯片与硅衬底间的硅硅键合,键合强度达到体硅强度。研制的差压型压力敏感芯片装配成传感器的零点温度漂移下降60%,静压误差下降约1个数量级。     

一种梳齿力平衡式微加速度计

讨论了一种多梳齿力平衡式微机械加速度计表头系统工作原理。因加速度计制造中存在的间距不对称,提出通过调节正负反馈电压比的方法来减小输出非线性误差,并得到了调节的约束关系式。通过体硅深宽比刻蚀和微键合工艺制造了加速度计并进行了封装,闭环电路实验测试得到在未修正系数前,加速度计在量程为-60～65 g时最大非线性误差为-0.8%,修正后满量程最大非线性误差为0.08%。试验结果与理论分析能很好地吻合,验证了方法的有效性。     

硅微陀螺仪器件级真空封装

为实现硅微陀螺仪真空封装以提高其性能,对硅微陀螺仪器件级真空封装技术进行研究.首先,设计硅微陀螺仪的专用陶瓷封装管壳,并采用钎焊技术进行封帽,采用金锑合金为焊料以满足封装过程中的高温.分析除气工艺对硅微陀螺仪品质因数的影响,除气试验结果表明,将硅微陀螺仪芯片和封装壳体放置在真空炉中进行高温烘烤,能有效地提高硅微陀螺仪的品质因数.制定硅微陀螺仪器件级真空封装的工艺流程,封装好的硅微陀螺仪的品质因数约为10 363.7,约为空气下的50倍.硅微陀螺仪品质因数跟踪测试结果表明,真空封装的硅微陀螺仪存储5个月后,其品质因数降低为最初的55.1%,这表明采用该器件级真空封装技术封装的硅微陀螺仪的真空保持度较差,有待进一步研究.     

谐振式MEMS压力传感器的制作及圆片级真空封装

为了提高传感器的品质因数,有效保护谐振器,提出了一种基于绝缘体上硅(SOI)-玻璃阳极键合工艺的谐振式微电子机械系统(MEMS)压力传感器的制作及真空封装方法。该方法采用反应离子深刻蚀技术(DRIE),分别在SOI晶圆的低电阻率器件层和基底层上制作H型谐振梁与压力敏感膜;然后,通过氢氟酸缓冲液腐蚀SOI晶圆的二氧化硅层释放可动结构。最后,利用精密机械加工技术在Pyrex玻璃圆片上制作空腔和电连接通孔,通过硅-玻璃阳极键合实现谐振梁的圆片级真空封装和电连接,成功地将谐振器封装在真空参考腔中。对传感器的性能测试表明:该真空封装方案简单有效,封装气密性良好;传感器在10kPa~110kPa的差分检测灵敏度约为10.66 Hz/hPa,线性相关系数为0.99999 542。     

内置皮拉尼计的硅通孔圆片级MEMS真空封装研究

针对现有的圆片级真空封装存在检测难、易泄漏等问题,提出了内置皮拉尼计的硅通孔圆片级MEMS真空封装方法。研制了用于圆片级真空封装导线互连的硅通孔,探讨了玻璃盖板与硅圆片之间阳极键合工艺与硅圆片与硅圆片之间的金硅共晶键合工艺,研制了用于检测封装壳体内部真空度的皮拉尼计; 研制了内置皮拉尼计的4英寸硅通孔圆片级真空封装,研制了低温激活非蒸散型吸气剂。实验研究表明,该研究解决了长时间保持真空度的问题。     

MEMS封装中阳极键合技术的影响因素研究和设计因素分析

结合MEMS气密性封装的需要,以玻璃与硅晶片阳极键合为例,给出阳极键合的封装工艺,从键合机理的角度研究了玻璃与硅阳极键合的影响因素,并就玻璃与硅阳极键合的设计因素做了分析,得到直径为100mm的Pyrex7740玻璃晶片和硅晶片在键合温度为500℃时,硅晶片的径向应力σrr=134.29MPa;键合后晶片的径向膨胀μ=0.1274mm。     

硅微陀螺仪器件级真空封装技术研究

为进一步提高硅微陀螺仪的品质因数及其稳定性,研究了硅微陀螺仪器件级真空封装的高真空获取技术和真空保持技术。首先,以硅微陀螺仪动力学方程为基础,分析了硅微陀螺仪的误差信号与品质因数之间的关系,并采用稀薄气体动力学分析具有高品质因数陀螺仪的空气阻尼。根据早期真空封装陀螺仪的品质因数跟踪测试曲线,分析了品质因数下降原因。采用程序升温脱附职谱分析法（TPD-MS）分析陶瓷管壳和金属盖板的放气特性,并选用了合理的吸气剂。最后,改进了器件级真空封装流程。测试结果表明,采用改进的器件级真空封装的陀螺仪品质因数最高可达162660,约为早期真空封装陀螺仪品质因数的14倍,且在一年内的变化小于0.05%。     

基于超声振动的阳极键合试验台设计

基于超声振动理论,针对当前阳极键合面临的键合温度较高、易产生残余应力对器件结构造成破坏等问题,在分析超声在机械加工中的应用后,创造性地将超声振动应用到MEMS封装中的阳极键合工艺中来,设计了一种键合强度高、试验温度低、结构简单、工作可靠的超声振动阳极键合试验台,为研制超声振动阳极键合机奠定了坚实基础,对于缩短阳极键合时间、降低阳极键合所需温度、提高MEMS器件的键合性能、满足实际生产需要具有重要意义。     

静电键合力引起硅微结构畸变的研究

硅微机械力敏器件在封装时往往采用硅—玻璃静电键合的方法。但在静电键合时静电力也往往作用于不需要键合的结构部分。并可能引起这些结构的畸变，造成器件特性劣化或破坏。本文分析了静电力的这些影响，并结合实践提出了一些解决方法     

MEMS器件的W2W真空封装研究

开发了一种适于MEMS器件的基于W2W(圆片对圆片)工艺的简易的圆片级真空封装方法。通过电镀工艺在MEMS器件圆片和封盖圆片上各沉积含5μm Cu和1.5μm Sn金属层的键合环。器件圆片和封盖圆片在160℃及0.01Pa的真空环境中保持10 min以形成真空,之后在270℃及4 MPa保持30 min通过Cu和Sn的互溶扩散工艺完成键合。测量键合区内Cu元素和Sn元素的重量比,证实形成了Cu3Sn和Cu6Sn5金属间化合物。通过剪切力测试对单个芯片的键合面强度进行标定,计算剪切强度达32.20 MPa。     

新型侧壁绝缘体硅微机械工艺

介绍了一种全新的体硅微机械工艺，可以取代SOI硅片而直接在普通硅片上对不同的侧壁电学导通部分进行绝缘。该工艺在DRIE形成的绝缘深沟内进行SiO2绝缘薄膜填充，并用填充后形成的SiO2条对器件侧壁进行电学绝缘。对于该工艺的原理、可能出现的问题、制作流程的摸索等进行了探讨，并且给出使用该工艺实现的一个带自检驱动功能的加速度计。该加速度计采用压阻原理，器件的压阻敏感电阻部分，通过在侧面进行半导体杂质扩散而形成。     

大尺寸垂直梳齿驱动MOEMS扫描镜

提出了一种采用垂直梳齿驱动器驱动的大尺寸、大扭转角度、低驱动电压微光机电系统（MOEMS）扫描镜。理论分析了垂直梳齿驱动器的工作原理,研究了垂直梳齿的制作工艺,采用体硅加工工艺结合硅-硅键合工艺制作了垂直梳齿驱动的MOEMS扫描镜。制作的扫描镜镜面尺寸为3 mm×2 mm,谐振频率为1.32 kHz。测试表明,该扫描镜镜面具有很好的光学表面,其表面粗糙度的均方根只有8.64 nm;扫描镜在驱动电压为95 V时可以实现最大2.4°的扭转角度;测得其开启时的响应时间为1.887 ms,关断时的响应时间为4.418 ms。     

电容式加速度计读出电路芯片设计

针对实验室的差分电容变化量为fF量级、频带宽度为0~20kHz的电容式加速度计,设计了一种可以有效减少噪声、失调电压和寄生电容影响的读出电路。该电路由开关电容积分电路、低噪声运放和单位增益采样保持电路组成。在0.5μm 2P3MCMOS工艺下完成该电路设计,通过仿真结果表明,该电路的输出电压与差分电容变化量成很好的线性关系,可以检测差分电容变化量达到fF量级。     

A monolithic silicon multi-sensor for measuring three-axis acceleration,pressure and temperature

A monolithic multi-sensor for small unmanned aerial vehicles is presented in the paper; it consists of a three-axis piezoresistive accelerometer, a piezoresistive absolute pressure sensor and a silicon thermistor temperature sensor. The accelerometer is designed with four silicon beams supporting the seismic mass and appropriate piezoresistors arrangement to detect three-axis acceleration and greatly reduce cross-axis sensitivities. For minimizing the effect of stress on the temperature sensor, the thermistor is designed along [100] and [010] crystal orientation. The multi-sensor is fabricated on SOI wafers by using MEMS bulk-micromachining technology. Some effective micromachining steps are applied in the fabrication. The two-step wet anisotropic etching process on the backside of the wafers can form the whole backside shape of the multi-sensor. The metal electrode sputtered on the Pyrex glass can avoid sticking between the Pyrex glass and the seismic mass in the process of anodic bonding. The die size of the multi-sensor is 4×6×0.9mm³. The measured results show that the multi-sensor is appropriate for its application field.     

Design and Analysis of MEMS Comb Drive Capacitive Accelerometer for SHM and Seismic Applications

This work presents the design of a MEMS accelerometer that is specifically intended for Structural Health Monitoring (SHM) applications where sensing low frequency low amplitude accelerations with high resolution is essential. The surface micromachined comb drive capacitance accelerometer structure has been considered in this design. The simulation experiments conducted on these devices using IntelliSuite MEMS design tool show that it has excellent displacement sensitivity of 21.39 μm/g, a capacitive sensitivity of 1.22 pF/g and voltage sensitivity of 1783 mV/g/V when it is designed to measure 0–0.1 g. Further, it is seen that it has a very low noise floor of 1.32 μg/√Hz and therefore high resolution. Since the accelerations can be as low as 0.04 g in SHM applications, excellent resolution is the primary goal in this design. Further, one more sensor specifically meant for strong motion seismic application has also been reported. This device has a bandwidth of 0–250 Hz and a noise floor of 5.612 μg/√Hz in addition to a sensor level voltage sensitivity of 97.9 mV/g/V. Finally, the comparison of these results with other similar devices reported in the past clearly illustrates the comparable performance of the present devices. Further, these devices, unlike the commercial low frequency accelerometers and other similar devices reported in the past can be fabricated by surface micromachining and CMOS compatible processes.     

Superconducting accelerometer using niobium-on-sapphire rf resonator

An accelerometer is described which uses a rf niobium-on-sapphire resonator as its sensor element. The accelerometer uses a magnetically levitated spool as a test mass and the spool modulates the inductance of the resonator; its position is servo controlled to maintain the resonator at the external rf excitation frequency. The accelerometer has high sensitivity over the full audio frequency range, but is optimized for frequencies between 100 Hz and 1 kHz, where the calculated displacement sensitivity approaches 10(-15) cm for a 1 Hz measurement bandwidth. The system noise sources are analyzed and possible improvements are discussed.     

基于MEMS技术梁膜结合压阻式加速度计的设计

提出了一种压阻式加速度计的新结构模型,采用梁膜结合结构方式,提高了低量程微硅压阻式加速度计的固有频率,减小了挠度对加速度计输出线性度的影响.通过有限元ANSYS仿真软件对结构模型进行静态和模态分析,发现在相同的负载条件下,新结构与传统结构相比,其固有频率平均提高了39%,挠度平均下降了39%,并对影响灵敏度、固有频率等主要指标的因素讨论分析,确定传感器的电阻分布和结构参数,对其结构进行优化.最后设计了版图及一套可行的工艺流程,采用各向异性化学腐蚀技术在单晶硅上制作压阻式加速度计,并与玻璃衬底阳极键合,从而提高加速度计的可靠性.该加速度计具有小尺寸、高频响、高精度的优点.     

Hardware comb filter enhances dynamic range and noise performance of sensors in noisy environments

We present the results of combining a hardware implementation of an analog comb filter with an ultralow noise electromagnetic sensor. The comb filter is designed to attenuate mains related interference, at either 50 or 60 Hz, and related harmonics. The sensor chosen for this work is an induction magnetometer, but the method is applicable to any low noise high dynamic range sensor. The resultant system, in this case, uses only a single coil, not a gradiometric configuration, thus providing a magnetometer capable of sensing field as opposed to field gradient. This combination of filter and sensor allows additional gain to be added and the full sensitivity of the system to be achieved, previously only realized in an electromagnetically screened room. At the same time, the high dynamic range, low noise performance, and original bandwidth of the sensor are maintained. The technique is illustrated by using the system in an urban environment to observe Schumann resonance phenomena. This approach to acquiring small signals in a noisy environment is compared with conventional analog filter and digital signal processing techniques.     

簧片式硅弹性膜应力分布的计算和加速度传感器的优化设计

为了提高我们已研制成功的新型簧片式硅加速度传感器的性能,用有限元法计算了不同形状和尺寸的质量块在４０ｇ值加速度作用下产生的应力分布,使我们优选了最佳的质量块设计方案,显著地提高了灵敏度,取得了与理论计算符合得很好的实验结果。     

Adsorption of fatty acids from alkane solution studied with quartz crystal microbalance

This paper describes the adsorption of the unsaturated fatty acids, oleic-, linoleic-, and linolenic acid onto steel coated quartz crystal surfaces from 2,2,4,4,6,8,8-heptamethylnonane as monitored by the quartz crystal microbalance (QCM) technique. It is shown that addition of fatty acid to the oil results in changes in bulk density and viscosity and that these changes must be considered before the sensed mass can be evaluated. The change in viscosity of the solution is larger for oleic acid than for linoleic acid and linolenic acid, which results in a larger correction for oleic acid with respect to bulk effects. After considering the effects due to changes in bulk properties, the influence of the viscoelastic properties of the adsorbed layer on the sensed mass was evaluated. The correction for the viscoelastic properties of the adsorbed layer was found to be very small for the systems studied. The sensed mass, at 1.1 weight percent, ranged from 0.5 mg/m² for oleic acid to 5 mg/m² for linolenic acid.