基于自解耦三明治结构的横向运动栅场效应晶体管MEMS微力传感器

本文介绍了一种基于横向可移动栅极场效应晶体管(LMGFET)的新型微型力传感器的开发。提出了一种精确的电气模型,用于小型LMGFET器件的性能评估,与以前的模型相比,其精度有所提高。采用了一种新型三明治结构,该结构由一个金交叉解耦栅阵列层和两个软光阻层SU-8组成。通过所提出的双差分传感结构,LMGFET横向工作在垂直干扰下的输出电流被大大消除,所提出传感器的相对输出误差从4.53%(传统差分结构)降低到0.01%。提出了一种实用的传感器制造工艺,并对其进行了模拟。基于LMGFET的力传感器的灵敏度为4.65μA·nN^(-1),可与垂直可移动栅极场效应晶体管(VMGFET)器件相媲美,但非线性度提高了0.78%,测量范围扩大了±5.10μN。这些分析为LMGFET器件的电气和结构参数提供了全面的设计优化,并证明了所提出的传感器在生物医学显微操作应用中具有良好的力传感潜力。

Monolithically integrated triaxial high-performance micro accelerometers with position-independent pure axial stressed piezoresistive beams

With the increasing demand for multidirectional vibration measurements,traditional triaxial accelerometers cannot achieve vibration measurements with high sensitivity,high natural frequency,and low cross-sensitivity simultaneously.Moreover,for piezoresistive accelerometers,achieving pure axial deformation of the piezoresistive beam can greatly improve performance,but it requires the piezoresistive beam to be located in a specific position,which inevitably makes the design more complex and limits the performance improvement.Here,a monolithically integrated triaxial high-performance accelerometer with pure axial stress piezoresistive beams was designed,fabricated,and tested.By controlling synchronous displacements at both piezoresistive beam ends,the pure axial stress states of the piezoresistive beams could be easily achieved with position independence without tedious calculations.The measurement unit for the z-axis acceleration was innovatively designed as an interlocking proof mass structure to ensure a full Wheatstone bridge for sensitivity improvement.The pure axial stress state of the piezoresistive beams and low cross-sensitivity of all three units were verified by the finite element method(FEM).The triaxial accelerometer was fabricated and tested.Results showing extremely high sensitivities(x axis:2.43 mV/g/5 V;y axis:2.44 mv/g/5 V;z axis:2.41 mV/g/5 V(without amplification by signal conditioning circuit))and high natural frequencies(x/y axes:11.4 kHz;z-axis:13.2 kHz)were obtained.The approach of this paper makes it simple to design and obtain high-performance piezoresistive accelerometers.

Novel resonant pressure sensor based on piezoresistive detection and symmetrical in-plane mode vibration

In this paper,a novel resonant pressure sensor is developed based on electrostatic excitation and piezoresistive detection.The measured pressure applied to the diaphragm will cause the resonant frequency shift of the resonator.The working mode stress–frequency theory of a double-ended tuning fork with an enhanced coupling beam is proposed,which is compatible with the simulation and experiment.A unique piezoresistive detection method based on small axially deformed beams with a resonant status is proposed,and other adjacent mode outputs are easily shielded.According to the structure design,high-vacuum wafer-level packaging with different doping in the anodic bonding interface is fabricated to ensure the high quality of the resonator.The pressure sensor chip is fabricated by dry/wet etching,high-temperature silicon bonding,ion implantation,and wafer-level anodic bonding.The results show that the fabricated sensor has a measuring sensitivity of~19 Hz/kPa and a nonlinearity of 0.02%full scale in the pressure range of 0–200 kPa at a full temperature range of−40 to 80°C.The sensor also shows a good quality factor>25,000,which demonstrates the good vacuum performance.Thus,the feasibility of the design is a commendable solution for high-accuracy pressure measurements.

Piezoelectric-AIN resonators at two-dimensional flexural modes for the density and viscosity decoupled determination of liquids

A micromachined resonator immersed in liquid provides valuable resonance parameters for determining the fluidic parameters.However,the liquid operating environment poses a challenge to maintaining a fine sensing performance,particularly through electrical characterization.This paper presents a piezoelectric micromachined cantilever with a stepped shape for liquid monitoring purposes.Multiple modes of the proposed cantilever are available with full electrical characterization for realizing self-actuated and seif-sensing capabilities.The focus is on higher flexural resonances,which nonconventionally feature two-dimensional vibration modes.Modal analyses are conducted for the developed cantilever under flexural vibrations at different orders.Modeling explains not only the basic length-dominant mode but also higher modes that simultaneously depend on the length and width of the cantilever.This study determines that the analytical predictions for resonant frequency in liquid media exhibit good agreement with the experimental results.Furthermore,the experiments on cantilever resonators are performed in various test liquids,demonstrating that higher-order flexural modes allow for the decoupled measurements of density and viscosity.The measurement differences achieve 0.39%in density and 3.50%in viscosity,and the frequency instability is below 0.05%o.On the basis of these results,design guidelines for piezoelectric higher-mode resonators are proposed for liquid sensing.