Micromachined accelerometers are one of the most widely used MEMS transducers. The theory of force-balance MEMS
accelerometers is presented in the thesis. Meanwhile the paper accomplishes the system-level simulation and analysis of
the force-balance MEMS accelerometer with different structure parameters. Based on the analysis, the conclusion is that
the parameters of folded-spring (such as the length of the beam, the width of the beam) especially influence the output
This paper presents a bulk micromachined gyroscope with fully symmetric and doubly decoupled structure. The fully
symmetric structure enables matched resonant frequencies of the drive and sense modes. The doubly decoupled
mechanism, which reduces the cross-coupling and the quadrature error, is realized by independent and folded
suspensions for restricting the drive and sense moveable fingers' degree of freedom (DOF). Additionally, the gyroscope
has large quality factors even operating at atmospheric pressure, which is designed by utilizing slide film damping
effects in drive and sense modes. Simulation results show that the resonant frequency for the drive and sense modes are
2776Hz and 2777Hz, respectively, and the cross-coupling is less than 0.2%. The gyroscope chip is fabricated by silicon-glass
anodic bonding and deep reactive ion etch (DRIE) technology. The fabricated gyroscope has a structure thickness
of 80 μm and a whole chip size of 5.5×5.5 mm<sup>2</sup>. The gyroscope has a static sense capacitance of 3.5 pF with minimum
capacitive gaps of 4 μm. The measured resonant frequency with damping is 2581 Hz with the quality factor of 195 at
The damping effects of MEMS inertial devices like micro accelerometers is studied. The damping analysis governing equation, the Reynolds equation, is the fundamental equation in this work. For small amplitude sinusoidal motions, which are governed by the linearized form of the Reynolds equation, both damping and compressibility effects are modeled numerically. Analytical solutions of the linearized Reynolds equation for micro inertial structures with various simple geometries are summarized. A procedure of solving the linearized model using typical commercial finite element analysis software is demonstrated. A numerical example of dynamical macromodel for a capacitive accelerometer indicates that viscous damping dominates at the dynamic characteristic of inertial devices. The theory and method of estimating damping effects for inertial devices with small amplitude motions are also presented. The theory is derived from the structural dynamic modal analysis and the simulation of the linearized Reynolds equation. The theoretical damping analysis equation for inertial microstructures is derived for the application of the small deflections. Simulation analysis can be used to compute the damping including the squeeze film and slip film cases. The method is applicable for general conditions, and makes it easy to make the dynamic lumped simulation model. It is useful at the beginning of the design of MEMS inertial devices affected by the damping effect.
A hybrid two-chip micro-accelerometer system consisting of a novel lateral capacitive silicon micro-acceleration sensor and a CMOS readout circuit is presented. The micro-acceleration sensor has a proof mass with the size of 0.6×2.4×0.1mm<sup>3</sup>, the mass of 380 μg and the capacitive gap of 6μm, fabricated by deep reactive ion etching (DRIE) and anodic bonding, using three masks. The CMOS readout circuit with a dynamic range of 75dB, a measured capacitive sensitivity of 10.7V/pF, can offer a self-test voltage of 7V by utilizing a charge pump circuit. The hybrid-integrated system with power supply of DC5V has a measured sensitivity of 18mV/g, 1KHz frequency bandwidth and nonlinearity of 0.18% within the measured range of 50g.
The miniaturized system is fabricated on the PMMA substrate including the CE separation chip and the PZT micropump chip. Adopted the PZT materials deformation as actuation force, the micropump is of the bi-direction flow capability to finish the self-rinsing process. The dimension of this micropump is 14×14×3 mm<sup>3</sup>. The volume of the pump chamber is about 20mm<sup>3</sup>. The pump can produce a maximum back pressure of 2m H<sub>2</sub>O and a maximum flow rate of 13 mL/min under 145 V, 100Hz squired wave power supply. The optimized capillary channel structure is chosen by the width of 50 μm, the depth is 20μm and the effective separating length is 50mm with round corner sinuous channel. The whole chip area is 55×20mm<sup>2</sup>.
A high-g overload protected piezoresistive accelerometer with the cave form section and two-end-fixed beams was introduced in this paper. Based on the finite element method (FEM) simulation, an optimal design of the microstructure was presented. The accelerometer was fabricated by standard IC process, ICP plasma etching and silicon anodic bonding technique. The testing results show that the accelerometer can bear 20,000g shock, the non-linearity reaches to 0.5% in the ±50g full scale, sensitivity reaches 0.8mV/g, and the operation frequency range is from DC to 2kHz.
In this paper a novel capacitive micro-vibration sensor with multi-folding beams, fabricated by bulk micromachining, is presented. The microstructures of the vibration sensor are simulated by the finite element method (FEM). The relations between the structural parameters and the sensitivity and frequency response of the sensor were considered in the simulation. The static and modal analyzing results of the sensors show that the higher sensitivity and mechanical strength with multi-folding beam structure were achieved. The microstructure with beam thickness under 400um can be fabricated with DRIE technology. When the area of silicon proof mass is 2.5×10<sup>5</sup> μm2, and the thickness of the proof mass vary from 40 μm to 80 μm, the mechanical noise is about 9×10<sup>-6</sup>g/√<i>Hz</i>. The sensor with resonant frequency up to 5kHz can be used to measure the vibration signal in a wider frequency range.
The configurations of electrochemical silicon etch-stop are discussed in this paper. An electrochemical etching machine with software and hardware, which can control the etching process of silicon very well, is designed and fabricated bas don the theory of electrochemical etching. Accurate etching temperature is obtained by modified integral algorithm of PID presented in temperature control in software. With an algorithm presented in control of etch-stop, the tech-stop point can be detected according to the characteristics of p- n junction current-time in electrochemical etching. The machine with hardware including S/H, controller and actuator can adapt to all wet etching configurations such as poly- electrode electrochemical etch-stop.
In this paper, the micro-fluxgate model of single core is presented. Under different excitation or external magnetic field conditions, the characteristics of the model were analyzed and then the structural parameters of the core were optimized by FEM. The simulation results show that: (1) the linear measurement range is 5.2e-7 to approximately 2.6e-4T; (2) the sensitivity is linear with the excitation frequency; (3) for Typel micro-fluxgate, a maximal sensitivity can be reached at 200KHz with the core width near to 0.7mm.