Haoxu Wang

A

This paper proposes a novel quartz micromachined gyroscope. The structure is designed by using shear stress detection method which can simplify the sidewall electrodes obviously. Furthermore, a tuning fork is introduced by the structure to obtain better differential vibrations. In order to increase the sensitivity of the sensor, the sense beam is designed to be a symmetric tapered beam. The device was fabricated using quartz anisotropic wet etching process. The drive mode frequency is 14.99 kHz, and the quality factor is 7600 in air. The sense mode frequency is 14.25 kHz, and the quality factor is 600 in air. Therefore, this gyroscope can operate at atmosphere pressure properly. The sensor is tested on a rate table through a specially designed readout circuitry. The sensitivity is 23.9 and the nonlinearity is 1.1% in range of . The noise floor is 0.1 .

{\rm Z}

Here we propose a novel quartz micromachined gyroscope. The sensor has a simple cross-fork structure in the x-y plane of quartz crystal. Shear stress rather than normal stress is utilized to sense Coriolis’ force generated by the input angular rate signal. Compared to traditional quartz gyroscopes, which have two separate sense electrodes on each sidewall, there is only one electrode on each sidewall of the sense beam. As a result, the fabrication of the electrodes is simplified and the structure can be easily miniaturized. In order to increase sensitivity, a pair of proof masses is attached to the ends of the drive beam, and the sense beam has a tapered design. The structure is etched from a z-cut quartz wafer and the electrodes are realized by direct evaporation using the aperture mask method. The drive mode frequency of the prototype is 13.38 kHz, and the quality factor is approximately 1,000 in air. Therefore, the gyroscope can work properly without a vacuum package. The measurement ability of the shear stress detection design scheme is validated by the Coriolis’ force test. The performance of the sensor is characterized on a precision rate table using a specially designed readout circuit. The experimentally obtained scale factor is 1.45 mV/°/s and the nonlinearity is 3.6% in range of ±200 °/s.

-Axis Quartz Tuning Fork Micromachined Gyroscope Based on Shear Stress Detection

A simple, fast, and cost-effective method was developed in this paper for the high-throughput fabrication of nanohole arrays on silicon (Si), which is utilized for antireflection. Wafer-scale polystyrene (PS) monolayer colloidal crystal was developed as templates by spin-coating method. Metallic shadow mask was prepared by lifting off the oxygen etched PS beads from the deposited chromium film. Nanohole arrays were fabricated by Si dry etching. A series of nanohole arrays were fabricated with the similar diameter but with different depth. It is found that the maximum depth of the Si-hole was determined by the diameter of the Cr-mask. The antireflection ability of these Si-hole arrays was investigated. The results show that the reflection decreases with the depth of the Si-hole. The deepest Si-hole arrays show the best antireflection ability (reflection 600 nm), which was about 28 percent of the nonpatterned silicon wafers reflection. The proposed method has the potential for high-throughput fabrication of patterned Si wafer, and the low reflectivity allows the application of these wafers in crystalline silicon solar cells.

A Z-axis Quartz Cross-fork Micromachined Gyroscope Based on Shear Stress Detection

The vibration characteristic analysis method for a quartz microgyroscope based on the admittance circle is reported in this paper. Admittance theory is introduced and the admittance circle principle is analysed to study the vibration characteristics of the quartz microgyroscope. The prototype gyroscope was fabricated by micro-electromechanical systems (MEMS) technology. The admittance and phase diagram of the work mode were obtained by vibration mode test systems. Then the admittance circle of the work mode was drawn, and the parameter identification of the transfer function between the voltage and current was completed to analyse the vibration characteristics. Therefore, the vibration characteristic analysis method based on the admittance circle can be used to build the transfer function of the quartz microgyroscope, which is helpful for the design of a high performance quartz microgyroscope.

Simple, fast, and cost-effective fabrication of wafer-scale nanohole arrays on silicon for antireflection

A novel quartz micromachined gyroscope is proposed in this paper. The novel gyroscope is realized by quartz anisotropic wet etching and 3-dimensional electrodes deposition. In the quartz wet etching process, the quality of Cr/Au mask films affecting the process are studied by experiment. An excellent mask film with 100 A Cr and 2000 A Au is achieved by optimization of experimental parameters. Crystal facets after etching seriously affect the following sidewall electrodes deposition process and the structure’s mechanical behaviours. Removal of crystal facets is successfully implemented by increasing etching time based on etching rate ratios between facets and crystal planes. In the electrodes deposition process, an aperture mask evaporation method is employed to prepare electrodes on 3-dimensional surfaces of the gyroscope structure. The alignments among the aperture masks are realized by the ABM™ Mask Aligner System. Based on the processes described above, a z–axis quartz gyroscope is fabricated successfully.

Vibration characteristic analysis method for the quartz microgyroscope based on the admittance circle

Structure optimization and simulation analysis of the quartz micromachined gyroscope are reported in this paper. The relationships between the structure parameters and the frequencies of work mode were analysed by finite element analysis. The structure parameters of the quartz micromachined gyroscope were optimized to reduce the difference between the frequencies of the drive mode and the sense mode. The simulation results were proved by testing the prototype gyroscope, which was fabricated by micro-electromechanical systems (MEMS) technology. Therefore, the frequencies of the drive mode and the sense mode can match each other by the structure optimization and simulation analysis of the quartz micromachined gyroscope, which is helpful in the design of the high sensitivity quartz micromachined gyroscope.

Fabrication of a novel quartz micromachined gyroscope

The design method for increasing gyroscope sensitivity is studied. By designing lumped parameter models of uni-mass, bi-mass, and tri-mass gyroscope structures, the influence between sensitivity and model parameters is analyzed. These three gyroscope structures are optimized in the same condition and the result shows that the sensitivity ratio of the three structures is 1:7:800 in the condition of frequency matching. Tri-mass structures high sensitivity shows its advantage in high performance design.

Structure optimization and simulation analysis of the quartz micromachined gyroscope

A simple and effective process based on nanosphere lithography for the fabrication of periodic inverted nanopyramid structure is presented in this article. The prepared nanostructure has almost a drop of 40% in the average reflectance at normal incidence, when compared with its corresponding bare silicon surface. Moreover, we obtained the reflection spectra for bare silicon substrate and prepared nanostructure through experiments and numerical calculations, and the results agreed well with each other, respectively. Therefore, we can combine the simulation method and fabrication method together to optimize the nanostructured antireflection coatings for better antireflection characteristics, and this methodology is robust and promising for the development of crystalline silicon solar cells. We further discussed the influences of pyramid size and the lattice constant of the nanopyramid array on the antireflection effect by numerical calculation, and we got a conclusion that the antireflection effect is positively correlated with the area-ratio defined as the ratio of the sum of the area of the nanopyramid holes in a unit cell to the area of a unit cell. Finally, we provide some direction and help for other researchers about the antireflection application of inverted nanopyramid arrays.

Sensitivity analysis and structure design for tri-mass structure micromachined gyroscope

The fabrication of quartz gyroscope is studied through the quartz wet etching experiments in this paper. The quartz gyroscope is made of quartz wafer covered by Cr/Au mask in etchant and need to form electrodes on the sidewall of quartz beam. The key problem in fabrication is two steps arris in on the sidewall because of anisotropy in quartz etching. 100Å Cr and 2000Å Au films are deposited at double sides of 500μm Z-cut quartz wafer as the etch mask. The quartz etchant was a mixture of HF and NH4F in proportions HF:NH4F = 1:1. Wet etching experiments are carried out every 5°C from 50°C to 80°C. Etch rate nonlinearly increases with temperature, and high temperature makes the roughness of sidewall surface increase. After 27h etching, the two steps arris are flatted because the etch rates of main surface on the quartz sidewall are different. This flatting process has been used in the fabrication of the gyroscope.

Antireflection characteristics of inverted nanopyramid arrays fabricated by low-cost nanosphere lithography technology

Schematic of a new type of Mach-Zehnder interferential magnetic sensor is illustrated. TbDyFe is used as the magnetostrictive material which is coated on the round surface of the sensing optical fiber. The deposition experiments are done using electron beam evaporation system. Three main process parameters, temperature, vacuum and deposition rate, which affect the TbDyFe deposition quality seriously, are analyzed by experiments. The deposited TbDyFe film is observed using electron microscope. The optimized parameters of TbDyFe coating with electron beam evaporation deposition method are acquired: temperature 350°C, vacuum degree 9.6×10−5 Pa and deposition rate 1Å/s.