Key Engineering Materials Vol. 503

Abstract: In order to realize more compact and in particular cost-effective spectrometers MOEMS technology offers attractive possibilities. Based Littrow spectrometer structure for the near-IR, a micro mirror grating spectrometer has been designed and developed. The ZEMAX was used for designed this structure. The resolution of this design is 10nm, the spectral range from 900nm to 1400nm. A scanning micro mirror is the key element of this IR spectrometer set-up. This micro mirror is driven by electromagnetic force. Before fix the micro mirror, it was calibrated. Meanwhile, for reducing the cost of this system, the silicon silt was designed and fabricated. For resolution testing of this spectral system, we used one light correction filters finished this experiment. The test result has shown the resolution of this spectrometer is16.8nm. Finally, the relation between the spectral line scanning characteristic and wavelength spectral resolution was discussed.

Abstract: Aiming at the problem that the dynamic attitude of small UAVs can’t be measured accurately, this paper describes a ground target positioning method based on the multi-images forward intersection. The parameters of the corresponding image rays are carried out in the local geographic coordinate system, and then these parameters are used to get the target 3-D coordinates. The flight tests have been finished. The test system is composed of a small UAV with a wingspan of 1.2 meters, a miniature vidicon and the micro autopilot developed by our laboratory. The miniature vidicon is calibrated with the active method and a red target is placed on the ground beforehand. In flight, the flight information including attitude, position .etc, is measured and recorded, and the video is collected isochronously. The error of the target position is about 5 meters at the flight height of about 250 meters.

Abstract: With development of MEMS pyrotechnics devices such as semiconductor bridge/metal bridges, the energy required to fuze ignition becomes smaller and smaller. The energy needed for traditional short-circuit is far greater than MEMS pyrotechnics devices explosive, and takes a large space of fuze, which does not accord with the smaller trend in fuse volume and ignition energy. This paper describes a MEMS short-circuit fuse based on electro-thermal theory, it has similar volume with MEMS pyrotechnics devices, and the energy required is less than the traditional shorts fuse. This short-circuit fuse has well safety features, short action time, small volume, low cost, and it is suitable to be used in fuse or other areas .

Abstract: This paper describes analysis of the S parameter of an X-band (8-12GHz) Wilkinson power divider by using odd-even mode, as well as full circuit analysis technique. The closed-form model of the S parameters versus normalized frequency response of the power divider is proposed for the first time according to our acknowledgement. The expressions are compared with the results obtained from a full-wave electromagnetic simulator (ADS) and found to yield acceptable agreement: the insertion loss is -3dB, the maximum difference of return loss of port 1 and isolation is about 0.17dB, the return loss of port 2 is less than -38dB.

Abstract: It is presented a fabrication processing of a two step method in deep silicon etching for MEMS applications using an the UK company Surface Technology Systems plc (STS), inductively-coupled plasma (ICP) etch technique STS ICP deep dry etching system. A brief introduction of schematic process of etching deep trenches on silicon substrate is first given, then with two step method for etching deep trenches. The film bulk acoustic resonator (FBAR) devices have been fabricated using STS ICP deep dry etching system with maximum etch rate of 4.6μ m/min, depth more than 450μm and sidewall roughness no more than 0.14μm. At the end of the second step process, the etch selective ratio of silicon to silicon oxygen is enhanced to ensure the device yield. At the same time, the negative effects such as microloads effects, footing effects, lag effects and micrograss effects are suppressed effectively.

Abstract: Wire bonding is one of the critical technologies of devices production, assembly and packaging in the microelectronic and MEMS field. During bonding process, the gold wires break easily, because the wires are repeatedly operated with high-speed. Therefore, the experiments were performed to analyze bonding process and the reason causing wire break. The results show that it is critical to prevent the broken wire to control the pressure wire pressure, the speed and angle of the pulling wire structure, the clamp gap, the capillary tip gap, and discharging energy in bonding process. the broken wire doesn’t occurs when the pressure wire pressure, the speed of the pulling wire structure, the angle of the pulling wire structure, the clamp gap, the capillary tip gap, the time and the current are 3-5g, 5rad/s and 10rad, 0.1-0.3mm, 1mm, 35ms and 10mA , respectively.

Abstract: This paper presents a fourth-order sigma delta (ΣΔ)modulator applied in micro-inertial sensors. After a introduction of sigma-delta modulator and its application in micro-inertial sensors, the system-level analysis and design is given and the gain coefficients is calculated. By the use of root locus, the stability of high order ΣΔ modulator is analyzed and it is got the minimum value of quantizer gain k is 0.287. The simulation shows that the signal to noise ratio (SNR) is 121.6 dB and the effective number of bits (ENOB) is 19.91 bits. When input level is smaller than -6 dBFs, the quantizer and integrators would not be overload and work well.

Abstract: Large-scale measurement of material property is not suit for the MEMS thin-film. Research the in-situ measuring method for material property of the MEMS thin-film is urgently. A center-anchored circular plate is adopted as the test structure here. The resonance frequency of the circular plate is measured to extract the Young’s modulus of a MEMS thin-film. The accuracy of this non-contact in-situ measuring method has been verified by CoventorWare. The inferences of the stress gradient have been analyzed. The advantages of the test structure and the measuring method present here also have been discussed.

Abstract: This paper presents analytical models for tri-axial accelerometer based on one seismic mass and eight beams. The model makes it possible to better understand and to predict the behavior of the accelerometer. The accelerometer discussed in this paper was designed to measure high g-forces in every single axis. We use finite element mechanics analysis and design for optimization of the device structure. FEA software ANSYS was used to simulate the behavior of the accelerometer when it was subjected to static high-g forces. The analytical results of simulation and theoretical demonstrate that the accelerometer we designed is feasible.

Abstract: Only when the tunneling gap is maintained near 10Å can the micromachined tunneling gyroscope operate regularly to generate tunneling current which is so weak that it would be submerged by the thermal-mechanical noise, 1/f tunneling noise and so on. At the meantime, the dynamic range of the device will be reduced drastically by the nonlinearity of the tunneling effect. So a controller must be designed for the miniature tunneling gyroscope to realize a 10 Å tunneling gap to decrease the nonlinearity and so as to enlarge the band-width of the device. At the other hand, the signal-to-noise ratio can be raised by the controller. Because of the anti-interference and robusticity of the LQG control theory and the time-varying characteristic of Coriolis acceleration, the preview-LQG control strategy is selected to design the closed-loop system. The simulation results suggest that the tunneling gap can be controlled near its nominal value and the measured input angular rate can be estimated accurately by the preview-LQG controller even if the input angular rate is a slowly time-varying random signal.