Key Engineering Materials Vols. 562-565

Abstract: Silicon nano pin arrays with heights of 1.3-3.66um and diameter of 315-899nm, are fabricated by CsCl self-assemble for CsCl nano islands for mask and ICP etching for silicon pins. CsCl film is firstly deposited on the wafer by thermal evaporation and putted in the humid controlled environment to be developed to the CsCl islands with diameter of 341-915 nm as self-assembled technology. Then the ICP etching with SF6, CCl4, He gas is introduced to make the silicon nano pin by the mask of CsCl nano islands, and the silicon nano pins with the different height of 1.3-3.66 um are finished for field emission. The gated FEA templates are fabricated by photolithography process and the lift-off technology with Ti-Si film as the gate electrodes. The final template for field emission has the silicon nano pins with diameters of 31.7 nm on top, Ti-Ag film with thickness of 105nm and gate holes of 30um in diameter, and SU8 resist insulator structure with thickness of 4um and holes of 10um in diameter. The optimization of the fabrication process and the performance for the configuration will be made.

Abstract: The surface with different water contact angle (θ_AW) was prepared through the use of self-assembled monolayers (SAMs) and the effect of water contact angle on the colonization of diatoms (Navicula sp and Pinnularia sp) and Ulva spores (Pertusa) was researched in an optional environment. Results revealed that the statistical adhesion density of colonized diatoms have a reciprocal-proportional relationship with θ_AW, and the adhesive force increase with the increase of θ_AW. However, it was the other way round for Ulva spores. Different with previous primary adhesion study, it also was revealed that diatoms have selectivity in colonization stage. All of these must due to their different reproduce (or grow) mode and extracellular polymers (EPS) composition.

Abstract: This paper presents the realization of omnipolar integrated magnetic switch based on GMR sensor, which was integrated with a specifically designed process IC by SiP technology. This integrated switch introduced hysteresis and adjustable sensitivity to improve its performance. When the gain was set to 2, its operation point and release point are 2.7|Oe| and 1.8|Oe| respectively. Its characteristics and function are verified by 2D Helmholtz coils and gear sensor test platform.

Abstract: In this paper the oxygen plasma dry release process for membrane-bridge RF MEMS switches is studied and several methods are used to improve the dry release process. The residual PR (Photoresist) on the device substrate after different process time are observed and measured in this paper. The measured data shows that the residual PR exponentially reduces with etch time. It is found that the residual PR on the bottom surface of the membrane bridge is more than that on the substrate. The completely released RF MEMS switch using oxygen plasma dry etch process is obtained.

Abstract: This article mainly focuses on the reliability of micro-spring, which as a typical component of MEMS device, applies electrodeposited nickel material and is fabricated by LIGA process, being used under the circumstances like transporting and restoring which may induce shock and crash. Griffith theory of brittle fracture and Abaqus FEA simulation software are applied for analyzing the probable failure modes of the micro-spring as overloaded. And the principle of elastic deformation, energy-time and displacement-time variation curves are given by three groups of simulation experiments. It proves to be one novel method to evaluate the reliability and accelerate exposing the failure mode of these MEMS components under dynamic circumstances in short period. After comparison, this method is proved reliable for analyzing and providing evidence for enhancing the reliability of the micro-spring, also improving the performance in micron size.

Abstract: Surface Acoustic Wave Filter (SAWF) is widely applied in military and civil fields as Radar, Broadcast, Television, etc. The SAWF that the central operating frequency exceeds 1 GHz is one of the key elements in modern high frequency communication system. In this paper, on the free-standing diamond film and silicon wafer substrates, two kinds of SAWF are manufactured. Based on the same IDT structure that the interdigital width is 3μm, the center frequency of ZnO/diamond structures can reach to 1.03 GHz, while the ZnO/Si structures is 120 MHz. The result express that the SAWF on the base of diamond can work in high frequency mode, while the Insertion Loss is high, reach to 23dB.

Abstract: Micro vibration energy harvesters have received much attention due to their potential application of low power wireless sensor networks and embedded systems. This paper studies three mechanisms to scavenge the ambient vibration energy, discusses the power management circuit and the application of the converter, investigates the prospective development and ongoing challenges in MEMS-based vibration energy harvester.

Abstract: A high-resolution humidity sensor based on MEMS FBAR with spin-coated PVA thin film is reported. The sensors exhibit very high sensitivity to water vapor and are able to detect down to 0.08 % change in relative humidity by monitoring the shift in series resonant frequency of the FBARs. The integration of these devices with CMOS oscillating circuits and RF front-end chips will create great potential of FBAR based mass sensors in a wide variety of applications in chemical and biological sensing.

Abstract: The characteristics of the ultrasonic energy transference system with MEMS ZnO square piezoelectric thin films array (SPTFA) structure has been investigated in the article. Design principle of the system has been introduced, and the ultrasonic directivity has been enhanced by the films array structure. The silicon panel with the SPTFA structure has been successfully fabricated based on MEMS technology. The ultrasonic energy transference experiment has been carried out as well in order to check the capability of the system by means of two SPTFA panel. Experiment results show that the maximum power density is 2.581mW/cm2 when the amplitude of exciting voltage is 10V, and the light emitting diode is lightened successfully by the system in a distance of 3mm.

Abstract: In order to obtain uniform temperature distribution in an embossing mold heated by induction used for replica of plastic gratings, temperature fields in the mold are analyzed by using electromagnetic-thermal coupling field of ANSYS software. The results indicate that the air gap between the induction heating coils and heating element, and the coils current density, have a great influence on the temperature distribution, while the exciting frequency has little. When an exciting current of 1636 A*N, frequency 25 kHz and heating time as 70 seconds, the optimal air gap width is of 4 to 5 mm. At the same time, reduce the exciting current densities can improve temperature uniformity on mold surface.