Search

This study has demonstrated the design and fabrication of wearable piezoelectric PDMS rubber microstructures with d31 and d33 modes. This PDMS microstructure shows a strong piezoelectricity with effective piezoelectric coefficient (d31) and (d33) of approximately 235 and 3350 pC/N, the lower effectively elastic modulus (E) and spring constant (k) are approximate 300 kPa and 250 N/m, respectively. PDMS microstructures have micrometer-sized voids inside and open channels, which can connect to ambient atmospheres. Internal patterns inside rubber electrets can be designed and adjusted its piezoelectricity, by means of utilizing multi-layer casting, stacking, surface coated with PTFE films, elastic gold films as flexible electrodes, and micro plasma discharge processes applied with a triangular waveform and electric field of 35 MV/m for 15 minutes at 100 °C to produce the functions as electrets. In conclusion, the piezoelectricity of PDMS microstructures could be tailored by adjusting the dimensions of the cellular voids, and potentially serve as wearable, stretchable MEMS devices with high sensitivities.

This study investigates the damage of the heterogeneous interface either dielectric oxide or metal materials induced by through silicon deep reactive ion etching (DRIE) process at the predefined bottom cavity area first time and establishes the failure model of the interface damage as well as metal re-deposition introduced by the silicon DRIE process. Thus, the DRIE process of low power and low frequency bias-RF is proposed to resolve the aforementioned problems by electrical testing verification. In applications, the Si-above-CMOS (TSMC 0.18μm generic CMOS process) process platform has been employed to demonstrate the present process approach. The fabrication results demonstrate that the problems of metal (or oxide) interface-layer damage and current leakage of CMOS-to-MEMS (or MEMS-to-MEMS) are prevented. Thus, the yield and performances of the capacitive motion sensors implemented using the Si-above-CMOS platform are significantly improved.

This study presents a novel "3D multi-function bio-sphere Drosophila (fruit fly) behavior platform" implemented by Micro Electro Mechanical System (MEMS) and flexible electronics technology. The 3D multi-function bio-sphere behavior platform has three merits: (1) The 3D MEMS bio-sphere provides a natural like testing environment (sphere space) for fly's behavior observation, (2) The integration of micro transducers (i.e. electric shock punisher, thermal punisher, and position sensor) enables various bio-experiments and the future potential of automatic training and recording, and (3) The transparent bio-sphere enhances the flexibility of bio-experiments through adding external visual learning targets and behavior monitoring camera. This is the first 3D Drosophila behavior training and recording platform for brain (learning and memory) experiments.

This study demonstrates a SOI condenser MEMS microphone consisting of planar interdigitated sensing electrodes, deformable diaphragm, and back chamber. No back-plate is required for this design, thus, the acoustic impedance is reduced. The merits of this study are: (1) the back-plate is replaced by planar interdigitated sensing electrodes to prevent in-use pull-in and process stiction between diaphragm and back-plate, (2) out-of-plane area-changing capacitive sensing provides a better linearity to sound pressure variation, (3) large and flat diaphragm implemented by SOI and DRIE process increases the acoustic sensitivity. The proposed microphone with 600µm diameter diaphragm and 42 pairs sensing electrodes is realized and tested. Measurements show a flat response between 1 kHz to 20 kHz. The sensitivity of microphone is −60.1dB (ref. 1V/1Pa) at 1 kHz.

A novel heater-with-holes design is developed to realize a CMOS-MEMS Pirani vacuum gauge. The Pirani vacuum gauge is a thermal-based pressure sensor consisting of heater and heat-sink units. The heat is conducted from heater to heat-sink through gas whose thermal conductivity changed with pressure. The proposed design has the following merits: (1) The holes on heater increase the thermal resistance and then improve the efficiency of heat transfer; (2) The heat-sink mesas are added to compensate the lost active area between heater and heat sink; (3) Easily integrate with other packaged CMOS-MEMS devices for pressure monitoring [1]. This study demonstrates two heaters with different hole-designs for concept proven. The devices have total die size of 206µm×82µm and 0.53µm sensing gap. Preliminary results show that the gauges have sensing range of 0.8–200torr and 0.2–200torr with sensitivity of 6.99×103(K/W)/torr and 8.15×103(K/W)/torr. The power dissipations are respectively 179.43µW and 127.59µW. In comparison, the conventional gauge containing heater w/o holes has sensing range 1–200torr with sensitivity of 0.91×103(K/W)/torr and power dissipation of 1117.34µW.

This study presents a large-area chip-network using polymer stretchable spring with embedded carbon nanotubes (CNTs). The CNTs as piezo-resistive sensing element and metal routing was located on the node and spring to achieve functional device. The mechanical and electrical connections of surrounding devices were linked by CNTs-polymer stretchable spring. The polymer spring stretches and expands the device nodes by several times of magnitude area to establish a 2D chip-network system. Merits of this approach: (1) polymer stretchable spring with large fracture strain acts as mechanical connection; (2) the polymer spring has better recoverability after stretching; (3) vertically-aligned CNTs are exploited as electrical routing and promising sensing material for different stress state; (4) the chip-network with flexibility can apply to curved surfaces.

This study has successfully designed and implemented the first normally-closed (NC) micro reed switch (Fig.1). The NC-type reed switch consists three separate metal structures (hinge, movable pad/spring, and fixed-pad) and is assembled by an attractive magnetic force exerted by an out-of-plane magnetic field. Furthermore, as applying a strong enough in-plane magnetic field, the spring is deformed by repulsive magnetic force to separate the pads and turn-off the switch (Fig.2). Merits of this NC reed switch: (1) liquid-metal to ensure electrical connection at hinge, (2) UV-gel fixed hinge structure, and (3) magnetized repulsive actuating mechanism. Experiment demonstrates a typical fabricated NC reed switch with driving magnetic field of near 160Gauss (G), and releasing at near 150G. The contact resistance is between 0.2–5Ω. The contact resistance variation is near 13% under a 20G excitation.

This study demonstrates the structural design and implementation of a single-axis MEMS vibratory rate gyroscope for the robustness improvement. As in Fig.1, features of this study are: (1) the employment of the fully-decoupled mechanism minimizes the mechanical cross-coupling between the drive-mode and the sense-mode; (2) the tuning fork structure combined with differential sensing architecture increases the resistance against external vibrations; (3) a compact structural design consists of the structurally forced (by rigid lever mechanism) anti-phase sense-mode and the linear-coupled anti-phase drive-mode. Preliminary results show a reduced coupling signal of near 500°/s, and the vibration resistances along different directions are also investigated. Moreover, the angular rate sensitivity is 17.7µV/°/s, which can be further improved using a mode-matched operation.

This study has presented a novel two-stage CMOS-MEMS capacitance-type tactile sensor with ER-fluid fill-in to extend the sensing range. Merits of the sensor are: (1) small tactile force (mN) is detected by first-stage sensing-unit with sensing range modulated by driving-voltage through ER-fluid; (2) larger tactile force (N) is detected by the second-stage sensing-unit. Moreover, sensing range and sensitivity can be further modulated using different ER-fluid. This tactile-sensor is implemented using TSMC 0.18µm 1P6M CMOS process, in-house post-CMOS releasing, ER-fluid filling, and parylene sealing process. Measurement results demonstrate the modulation of sensing ranges are 0∼50mN (as the bias-voltage for ER-fluid is 0–1V), and 0∼90mN (as the bias-voltage for ER-fluid is 10V); sensitivities are 0.15fF/mN (bias-voltage for ER-fluid is 0-1V) and 0.1fF/mN (bias-voltage for ER-fluid is 10V) for first-stage. Moreover, the second-stage has a larger sensing range (0∼2.5N) and the sensitivity can also be modulated by bias voltage (3.55fF/N for 0.5V and 3fF/N for 5V).

This study is an extension of MR fluid (MR fluid: liquid glycerol polymer with magnetic-particles) applications on MEMS devices [1-2], presenting a novel moving technology for MR fluid using the rotation of chainlike magnetic particles (Fig.1). When driven by in-plane dynamic magnetic field, the chainlike magnetic particles inside MR fluid are rotated out-of-plane and further encourage the motion of MR fluid (Fig.1b). MR fluid movement speed and direction can be modulated by (1) weight fraction and chain length of magnetic powder; (2) strength and angular speed of applied magnetic field (Fig.1b); (3) pattern of spiral channel (Fig.1c-d). MR fluid movements are demonstrated on three PDMS dome shaped substrates [3] with no channel, clockwise spiral and counterclockwise spiral channels (Fig.1b-d). Measurement results are summarized in Table 1. Detail investigations are still required to quantitatively predict and precisely control the movement of the MR fluid.

Vertical comb drive actuator has been widely employed in MEMS scanning mirror, but more process challenges occur when it goes to high aspect ratio comb structures for high stroke application. This paper reports a novel process to fabricate self-aligned vertical comb drive actuator with aspect ratio up to 40. With this process platform, some process limitations can be lifted, while a vertical comb drive actuator with non-resonant scan angle larger than 20° can be obtained. A 2D scanning mirror with large scan angle is taken as an example to demonstrate this platform.

This study has demonstrated a novel micro testing device to easily fabricate/integrate the thin film specimen, and further improve the measurements of thin film tensile test by considering the out-of-plane deformation (Fig.1). Due to “nominally-clamped” boundary condition [1] from microfabrication, additional bending moment is introduced during tensile test and cause the specimen an out-of-plane deformation. This study exploits such characteristic to determine thin film elastic modulus and modify the measured fracture strain. Merits of proposed tensile test approach: (1) the presented processes could fabricate/integrate different thin film specimens for testing; and (2) out-of-plane deformation of specimen is considered and precisely measured by interferometer (sub-nm resolution). The test-unit is implemented on Silicon-on-insulation (SOI) wafer. In applications, the mechanical and electrical properties of evaporated gold films are characterized.

Effect of pre-nucleation techniques on enhancing nucleation density and the adhesion of ultra-nanocrystalline diamond (UNCD) deposited on the Si substrates at low temperature were investigated. Four different pre-nucleation techniques were used for depositing UNCD films: (i) bias-enhanced nucleation (BEN); (ii) pre-carburized and then ultrasonicated with diamond powder solution (PC-U); (iii) ultrasonicated with diamond and Ti mixed powder solution (U-m); (iv) ultrasonicated with diamond powder solution (U). The nucleation density is lowest for UNCD/U-substrate films (∼ 10 8 grains/cm 2 ), which results in roughest surface and poorest film-to-substrate adhesion. The UNCD/PC-U-substrate films show largest nucleation density (∼ 1 × 10 11 grains/cm 2 ) and most smooth surface (8.81 nm-rms), whereas the UNCD/BEN-substrate films exhibit the strongest adhesion to the Si substrates (critical loads = ∼ 67 mN). Such a phenomenon can be ascribed to the high kinetic energy of the carbon species, which easily form covalent bonding, Si–C, and bond strongly to both the Si and diamond.

This paper presents a simplified friction clutch design, which consists of the dual Belleville spring and the friction plates. This design exploits the preset angle on the Belleville spring to increase the friction area during operation; thus, the load on spring is reduced at a given transmitted torque. Due to the increasing of friction area, the Belleville spring can also act as a friction plate, and the components required for the clutch can be reduced. The maximum transmittable torque of the clutch is easily adjusted by varying the preload on the Belleville spring. Moreover, it is very easy to assemble the components of the present clutch. To demonstrate the present design, a prototype friction clutch with a Belleville spring has been fabricated and tested. We showed that the transmitted torque remained constant for different operating speeds.

A novel method has been developed for the manufacture of a three-dimensional multi-electrode array (3D MEA), particularly, the shape of micro-tips can be varied by MEMS technology to construct different multi-electrode array. It improved the disadvantage of single electrode, which meant that it was available for multi-recording and analysis of a series of signals. Overcoming the difficulty of making interconnection line on 3D MEA chips via innovative fabrication process design. Using local isolation and removal of oxide films to forming electrodes and interconnections with oxide isolation covers. A 10 × 10 3D MEA with a distance of 100m between each other for further bio-neural signals was demonstrated, and a test on rabbit retina was also available. Besides, integrating pre-amplifier and built-in resistors with 3D MEA was brought out to hopefully increase the efficiency of sensing.

This study reports a novel method for tuning the deflection profile of micromachined cantilever by means of multiple plasma surface modification. In short, the shape and curvature of the cantilever can be tuned using the combination of plasma treatments along the beam length and the beam width, respectively. To demonstrate the feasibility of this approach, various NH 3 plasma treatments were employed to tune the deflection profile of cantilevers made of SiO 2 film. The deflection profiles predicted by the simulation and analysis agree with that determined from measurement.

This work presents a miniaturized tracking and focusing optical pickup head implemented using MEMS technology. The device was fabricated by poly-Si trench-refilled technology and used a UV-cured polymer droplet or micro ball lens as the objective lens. A bidirectional vertical comb-drive actuator and V-beam thermal actuator drove the objective lens for the out-of-plane (focusing) and in-plane (tracking) motion, respectively. In applications, various tracking and focusing devices have been successfully fabricated and characterized. The upward and downward displacement of the focusing optical pickup head is 2.9 and 1.7 µm, respectively; the in-plane displacement of the tracking optical pickup head is ± 46.7 µm. The resonant frequencies of the focusing and tacking systems are 2.3 and 8.5 kHz respectively. In addition, the UV-cured polymer lens and solid micro ball lens were both successfully integrated with a MEMS device to create an objective lens.

Magnetic induction heating is a promising heating approach for MEMS processes and devices. This study has discussed the scale effect of induction heating for thin-film microstructures through analytical and experimental means. The results show that the temperature increase varies with the in-plane surface area of the microstructure and the relative permeability of thin-film materials. Moreover, the shape of the microstructure also leads to the difference of temperature increase. In applications, localized heating and various temperature regions can be simultaneously achieved on the substrate by applying an external high-frequency magnetic field.

This work presents a miniaturized two-degree-of-freedom (2-DOF) optical pick-up head implemented using MEMS technology. This device contains novel bi-directional vertical comb-drive actuators to act as the focusing positioner, and V-beam thermal actuators to serve as the tracking positioner. In addition, a UV-cured polymer droplet is used for an objective lens. Particularly, the focusing and tracking actuators are monolithically fabricated and integrated in a single device. Electrical routing and isolation is also available by poly-Si and Si3N4 multi-layers for 2-DOF operation. In applications, the proposed device has been successfully fabricated and characterized. The upward and downward displacements of the focusing optical pick-up head are 4.6 ?m and 4.1 ?m, respectively, at a 30 V driving voltage. And the in-plane displacement of the tracking optical pick-up head is ?16.3 ?m, at a 5 V driving voltage. The resonant frequencies of the focusing and tacking systems are 1.9 kHz and 4.1 kHz, respectively.

This work attempts to integrate poly-Si thin film and single-crystal-silicon (SCS) structures in a monolithic process. The process integrated multi-depth DRIE (deep reactive ion etching), trench-refilled molding, a two poly-Si MUMPs process and (1 1 1) Si bulk micromachining to accomplish multi-thickness and multi-depth structures for superior micro-optical devices. In application, a SCS scanning mirror driven by self-aligned vertical comb-drive actuators was demonstrated. The stiffness of the mirror was significantly increased by thick SCS structures. The thin poly-Si film served as flexible torsional springs and electrical routings. The depth difference of the vertical comb electrodes was tuned by DRIE to increase the devices' stroke. Finally, a large moving space was available after the bulk Si etching. In summary, the present fabrication process, named (1 1 1) MOSBE (molded surface-micromachining and bulk etching release on (1 1 1) Si substrate), can further integrate with the MUMPs devices to establish a more powerful platform.

In this study, a novel HARM (high aspect ratio micromachining) micromanipulator fabricated on (1 1 1) silicon wafer is reported. The micromanipulator consists of a positioning stage, a robot arm, supporting platforms, conducting wires, and bonding pads. These components are monolithically integrated on a chip through the presented processes. The three-degrees-of-freedom (3-DOF) positioning of the micromanipulator is realized by using the integration of two linear comb actuators and a vertical comb actuator. The robot arm is used to manipulate samples with dimension in the order of several microns to several hundred microns, for instance, optical fibers and biological samples. The robot arm could be a gripper, a needle, a probe, or even a pipette. Since the micromanipulator is made of single crystal silicon, it has superior mechanical properties. A micro gripper has also been successfully designed and fabricated. © 2005 Published by Elsevier B.V.

This study has successfully demonstrated a process to localize, assemble and weld microstructures using an external magnetic field. The primary three merits of this technology are as follows. (1) The magnetic field is not only to assemble the microstructures but also to fix them by induction welding. (2) The assembly and welding can be localized by the magnetic film. However, a global wafer level process can be achieved by the magnetic field. (3) It is easy to tune the heating temperature by varying the area of the magnetic film; in other words, photolithography can define various temperature regions on a substrate.

Combining a new H-beam actuator, movement link structure, reflective micro-mirror, and arched buckle spring to demonstrate a new compact latched 2 × 2 optical switch device is first reported. This novel H-beam actuator can generate bi-directional static displacement and bi-directional motion. Optical switch using this H-beam actuator is well functioned and exhibits good optical characteristics with industrial level performance. The measured optical switching characteristics include switching time of 5 ms under a 25 V dc pulse, back reflection loss of −52 dB, cross-talk of −60 dB, insertion loss of 0.8 dB, polarization-dependent loss of 0.03 dB, and wavelength-dependent loss of 0.11 dB.

A simple method of protecting film bulk acoustic resonator (FBAR) filters by wafer-level packaging is proposed. This method employs a reliable silicon microcap structure to encapsulate FBAR filters. Since only conventional processes and facilities were required to accomplish this work, it is a cost-effective way to package FBAR filters. The fabrication process consists of three steps: cavity etching, wafer bonding and wafer singulation. In this study, the design and fabrication processes are described in detail. Moreover, a filter designed for personal communication systems (PCS) transmitter band is measured to demonstrate the performance variation after the microcap process. The fabrication results and measurement results have ensured the effectiveness of this process.

This study presents a bulk micromachining fabrication platform on the (100) single crystal silicon substrate. The fabrication platform has employed the concept of vertical corner compensation structure and protecting structure to integrate the wet anisotropic etching and DRIE processes. Based on the characteristics of wet anisotropic etching and DRIE, various MEMS components are demonstrated using the bulk micromachining platform. For instance, the free suspended thin film structures and inclined structures formed by the {111} crystal planes are fabricated by the wet etching. On the other hand, the mesas and cavities with arbitrary shapes and the structures with different leve l heights (or depths) are realized by the characteristics of DRIE. Since the aforementioned structures can be fabricated and integrated using the presented fabrication platform, the applications of the bulk micromachining processes will significantly increase.

The technology challenges for miniature optical pickups include high-numerical-aperture objective lens design, servo actuator functions and performance, and component assembly tolerance. In this paper, a microelectromechanical systems (MEMS)-based miniature optical pickup is proposed for DVD and blue disk systems. A high-order diffractive objective lens with a continuous surface relief is designed. Focus, tilt, and tracking servos are implanted with MEMS micro actuators. Preliminary design and test results are presented.

A novel dual-directional actuation technique to determinate the in-plane and out-of-plane dynamic response of the microstructure is presented in this study. The dual-mode ultrasonic array transducer has been realized to simultaneously generate the in-plane and the out-of-plane pulsed bulk acoustic waves (BAW). Thus the array transducer can be exploited to excite the micromachined structures. This array transducer, which acts as a vibration exciter during the vibration test, is named the dual-mode BAW hammer. The performance of the dual-direction hammer was designed and simulated by the commercial finite element analysis software. In application of this technique, the micromachined cantilevers were employed to conduct the vibration test. Experimental results showed that the in-plane and the out-of-plane vibration modes of micro beams were simultaneously excited using the dual-mode BAW hammer. Since the sample and the measurement apparatus are very simple, this approach has the potential for wafer level on-line testing.

The nanoindenation testing system has been extensively applied to determine mechanical properties of thin film presently. However, the contact surface between the indenter and the thin film may arise a sliding friction. The existing report ignores such a friction force effect at the contact surface. This study will present several experimental results to demonstrate the existing of the friction force between the tip of the indenter and the test sample. In this regard, the effect of the sliding friction on thin film mechanical property measurement will be discussed. According to the experiment results, the friction force effect is influenced by the indent depth. In addition, the interface friction force is more significant for the brittle material due to its larger elastic restoring force. The ignorance of the friction effect may lead to significant error when extracting elastic modulus of thin films from the indentation test.

This work integrates multi-depth DRIE etching, trench-refilled molding, two poly-Si layers MUMPs and bulk releasing to improve the variety and performance of MEMS devices. In summary, the present fabrication process, named MOSBE II, has three merits. First, this process can monolithically fabricate and integrate poly-Si thin-film structures with different thicknesses and stiffnesses, such as the flexible spring and the stiff mirror plate. Second, multi-depth structures, such as vertical comb electrodes, are available from the DRIE processes. Third, a cavity under the micromachined device is provided by the bulk silicon etching process, so that a large out-of-plane motion is allowed. In application, an optical scanner driven by the self-aligned vertical comb actuator was demonstrated. The poly-Si micromachined components fabricated by MOSBE II can further integrate with the MUMPs devices to establish a more powerful MOEMS platform.

The study investigates the vibration characteristics of the micromachined free–free beam through analytical and experimental means. In application, this study employed the resonant frequency of the micromachined free–free beam to successfully extract the elastic modulus of a thin film. As a comparison, the vibration characteristics of a micromachined cantilever have also been studied. This study demonstrates that the micromachined free–free beam is a better test key to extract the thin film elastic modulus when the wafer experiences a relatively long etching time. Moreover, the micromachined cantilever gives a lower bound and the micromachined free–free beam gives an upper bound while determining the thin film elastic modulus. Since the free–free beam is a previously fabricated and modeled micromachined structure, it can be employed as a supplement test key to the cantilever beam approach.

In general, convex corner structures and non {111} crystal planes will be undercut during wet anisotropic etching. These characteristics have been extensively exploited to fabricate freely suspended thin film structures. On the other hand, these effects have to be reduced or prevented in various applications. This study has successfully demonstrated a novel process to exploit the characteristics of DRIE to assist wet anisotropic etching. To this end, protecting structures including vertical posts and vertical walls were employed to protect convex corners and non {111} crystal planes from undercutting. In applications, the experimental results show that mesas and cavities with arbitrary shapes can be fabricated using wet anisotropic etching. Moreover, these mesas and cavities can further integrate with suspended thin film structures and the structure formed by the inclined {111} crystal planes. Hence, the variety of bulk micromachined MEMS devices will significantly increase.

The BELST process has been proposed and it has demonstrated the capability to overcome anchoring and depth controlling issues in many high-aspect-ratio micromaching (HARM) processes. However, the actuation mechanisms are still restricted to in-plane motion only. In this study, a novel fabrication process called BELST II has successfully been developed. Moreover, the BELST II process was employed to fabricate a novel electrostatic vertical comb actuator (VCA). Three advantages for this VCA can be observed. First, through some exquisite designs the fabrication process has no critical alignment and bonding problems. Secondly, the relative vertical position between the moving and the stationary fingers can be adjusted freely to optimize the performance of the VCA. Thirdly, both a large mirror structure and trimmed torsional spring are available through this process. Thus, improved performance regarding enlarged traveling distance with reduced driving voltage can be obtained. In the application of the BELST II process, various HARM devices were realized, such as an optical scanner mirror and variable optical attenuator driven by the VCA.

In this paper, we give the reasons for the phenomenon of adhesion of U-shaped electrothermal actuators onto substrates which is commonly observed for such devices. Next, we identified a significant advantage for operating these U-shaped actuators on top of a polysilicon layer with a suitable pattern design. A thorough investigation on the deflection behavior of actuators with different dimensional parameters, i.e., cold arm width, flexural beam length and hot arm length, was carried out. Finally, we discussed the effects of electrostatic force on the actuator due to these parameters. Based on these analyses, we suggested optimized dimensions for the U-shaped actuator.

A novel micromachined torsional mirror for use as an optical scanner is reported in this study. The proposed micromachined torsional mirror exploits novel electrostatic actuators and a reinforced thin-film mirror plate to improve the performance of the device. The electrostatic actuator is actuated by near gap-closing electrodes so as to decrease the driving voltage. Moreover, the actuator employs a lever mechanism to magnify its output displacement. A torque generator is implemented by combining two electrostatic actuators, which prevents the mirror plate from wobbling. A reinforced rib is used to stiffen the thin-film mirror plate to improve the optical performance of the scanner. In order to demonstrate the proposed concept, micromachined torsional mirrors were fabricated through the integration of DRIE, surface, and bulk micromachining processes. Measurements revealed that the proposed torsional mirror could operate at a low driving voltage, the scanning frequency of the mirror can reach 17.7 kHz, and the optical scan angle is 5°.

In this study, a resonant technique to characterize the Poisson’s ratio of thin film materials is proposed. The diagnostic micromachined cantilevers are fabricated using the thin film to be determined. The Poisson’s ratio of the thin film can be determined after the bending and torsional vibration modes are measured. To obtain cantilevers with prismatic cross section, the micromachined beams were fabricated on the (1 1 1) silicon substrate. The primary advantage of this technique is that the error of Poisson’s ratio due to the deviation of film thickness can be significantly reduced. In application of this technique, the Poisson’s ratio of thermally grown silicon dioxide is measured to be 0.202±0.021.

Out-of-plane electrothermal actuators have been applied to a variety of fields with the bimorph effect being the most commonly used driving method, due to simple fabrication process. However, such an actuator experiences a shear force at the interface of different materials, while actuated. Delamination therefore takes place and decreases its lifetime. In this study, a novel bi-directional out-of-plane electrothermal actuator is designed and fabricated. Unlike the bi-metal and hot–cold arm thermal actuator, this actuator can move in two directions. Since this actuator is consisted of only single-layer thin film material, it can prevent from delamination. According to the static load–deflection test, this actuator can achieve bi-directional actuation with amplitude near 6–7 μm when driven at 5 V. According to the vibration test, the dynamics of the actuator is influenced not only by the thermal characteristics but also by the vibration modes. Consequently, the thermal actuator still has a significant output when driven near 40 kHz. The actuator were experienced a fatigue test which shows that its resonant frequency remains unchanged after 10 9 cycles of continuous operation with driving voltage at 2.25 V.

A fully differential CMOS-MEMS double-ended tuning-fork (DETF) oxide resonator fabricated using a 0.18-μm CMOS process has been demonstrated with a Q greater than 4800 and more-than-20-dB stopband rejection at 10.4 MHz. The key to attaining such a performance attributes to the use of oxide structures with embedded metal electrodes, where SiO2 offers a Q enhancement (at least a 3-times-higher Q) as compared to other CMOS-MEMS-based composite resonators with similar structures and vibrating modes and where flexible electrical routing facilitates fully differential configuration to suppress capacitive feedthroughs. In addition, the resonators developed in this work possess a positive temperature coefficient of frequency (TCf) and mode-splitting capability, therefore indicating a great potential for temperature compensation and spurious-mode suppression, respectively. This technology paves a way to realize fully integrated CMOS-MEMS oscillators and filters which might benefit future single-chip transceivers for wireless communications.

A novel integrate micro magnetic pillar array with anisotropic magneto-resistive (AMR) structure for out-of-plane magnetic field detection has been proposed and demonstrated. The merits of this study are: (1) The magnetic pillar converts magnetic field from out-of-plane to in-plane and provide magnetic gain (G) where G≈1/N (N:demagnetization factor) [1]; (2) The micro magnetic pillar array can be batch fabricated and defined at appropriate locations, and further monolithically integrated with AMR sensor; and (3) The magnetic conversion efficiency can be easily further enhanced by increasing the density of magnetic pillar array. The AMR sensor with different magnetic pillar density has been implemented and measurements indicate that the AMR sensor with larger density of magnetic pillar array has better sensitivity and resolution for detecting out-of-plane magnetic field.

This paper reports a high-sensitivity and high-speed capacitive humidity sensor. A novel capacitive vertical parallel-plate (VPP) array had been monolithically integrated with an on-chip ring oscillator (RO) using the standard TSMC 0.18µm CMOS process and subsequent in-house post-processes. Resorcinol-formaldehyde (RF) aerogel, a new kind of moisture-sensitive polymer, was deposited and defined in columns in the VPP array. Measurements show that the typical fabricated device has a sensitivity of 0.566% capacitance change per percent-relative-humidity (%RH) and a response time of 6s. The monolithic integration of the humidity sensor with RO is also demonstrated to provide a sensitivity of 3.8 kHz/%RH. Further improvement in sensitivity is required by varying the operating frequency of RO.

Improvement of a bulk acoustic wave (BAW) hammer for vibration test of microstructures using 1-3 composite transducers is presented. The characteristics of a BAW hammer produced with the 1-3 composite transducer were simulated by commercial software PIEZOCAD. The composite transducer excited by the pulse waveform acted as a BAW hammer will be evaluated by the vibration testing of microstructures. The experimental results of a BAW hammer with composite structure agree well with the simulation predictions. Moreover, based on the vibration testing result of silicon dioxide beams, 1-3 composite transducers excited by a pulse can improve the waveform duration and bandwidth of BAW hammer used in the vibration testing. Furthermore, the program code can be exploited to design the composite BAW hammer to excite the interested frequency range of the microstructure. The BAW hammer produced by the 1-3 composite transducers is also applicable to the on-line testing of microstructures.

High-aspect-ratio micromachining (HARM) developed in recent years has made many devices more versatile compared to the surface micromachining process, but it has also met some challenges which have not occurred before. Those issues made many restrictions on HARM structure design, including structure thickness/width limitations, anchor-induced design problems, thickness uniformity and sidewall conductivity problems, which are discussed in this paper. Accordingly, we propose a novel boron etch-stop assisted lateral silicon etching (BELST) process which employs the (111) wafer process and heavy boron diffusion. Many design constraints have been reduced through some delicate designs of the BELST process. Furthermore, the process is capable of various applications, and has been applied in fabricating a dual mass-spring resonator and a micro vibrating gyroscope in this work. In summary, the developed BELST process can possess most existing merits as well as reducing many design constraints in the existing HARM process, and is expected to contribute in making HARM more competitive and convenient.

A novel testing technique to determinate the dynamic response of the microstructure is presented. In this study, a bulk acoustic wave (BAW) hammer generated by a pulsed ultrasonic transducer is used to excite the microstructures. Thus, the dynamic response of the microstructure in a wide frequency range is excited. Based on this novel method and test apparatus, the dynamic response of the microstructure including the resonant frequency, mode shape and the modal damping of the microstructure can be measured in a single excitation. Experimental results of the microbeams with different length agree well with theoretical predictions. In summary, the proposed BAW hammer technique has the following advantage: the sample preparation for this approach is very easy since it is not necessary to deposit an additional film for thermal or electrical purpose. In this regard, the experimental results of this technique are more accurate since there is no additional film to influence the dynamic behavior of the test sample. Moreover, there is no uncertain side effect such as thermal and acoustic coupling, caused by this approach. Since the test apparatus is also very simple, this approach has the potential to do the on-line test for batch production.

A micro-electro–mechanical system (MEMs) technique, the bilayer cantilever beam method was used to examine the residual stress and the thermal expansion coefficient (α) of TaOxNy films by measuring the changes in radius of curvature. Residual stresses of all the TaOxNy films RF-deposited onto SiO2/Si (100) are compressive and varied from 2.5 to 12.5 MPa. The compressive stress is inversely proportional to the N2/O2 flow ratio except that appears at the flow ratio 0.5. However, the calculated α values, ranging from 7×10−7 to 2×10−5 °C−1, increase proportionally with the N2/O2 flow ratio, except the value appears at the flow ratio 2. Comparing the α values of ZnS/SiO2 and Si3N4 films, the properties of TaOxNy films being optimizable by adjusting the N2/O2 flow ratios are obviously promising candidates in optical recording applications. Effects of other processing parameters on the α value and stress, such as the film thickness, RF power and reactive gas ratios during deposition, are also elucidated. Furthermore, a load-sensing nano-indentation method was used to examine the elastic property of the films. The obtained reduced elastic modulus Er values of TaOxNy films are nearly constant (∼200±15 GPa) at the N2/O2 flow ratio from 0.25 to 2.

The undercut process of the micromachined structures on a (1 1 1) oriented silicon wafer is studied in this paper. As observed in the experiment, the undercut of a cantilever on (1 1 1) wafer is along the width of the beam. According to the undercut mechanism, the advantages of fabricating a cantilever on (1 1 1) wafer are three-fold: (1) significantly reduce the etching time and obtain an ideal clamped boundary in the mean time; (2) the thickness as well as the moment of inertia of the cantilever is closer to the ideal case; (3) the flexural rigidity of the cantilever is constant along the beam axis. Consequently, the micromachined cantilever on a (1 1 1) wafer is more appropriate in various applications. For instance, it is more appropriate to fabricate the diagnostic microstructures on the (1 1 1) wafer than on the (1 0 0) wafer in determining the thin film residual stress.

A novel antistiction method using harmonic excitation on the microstructure is presented. We exploit a simplified model consisting of a single-degree-of-freedom mass-damping-spring system to simulate the drying process of the microstructure. Based on this proposed method, we can predict the dynamic response of the microstructure including the resonant frequency and the damping characteristic of the drying system. And then adequate harmonic excitation is applied to release the microstructure during drying process. Silicon dioxide beams with 0.7-μm-thick, 16-μm-wide, 120-μm-long, 4 μm gap, were released successfully by this method. Theoretical predictions of the dynamic behavior of microstructures during the drying process agree well with experimental results. The proposed approach effectively improves the yield rate of the microstructure without additional masks and complicated process during the postetch release process.

V-shaped beams are widely applied for the suspension of the sensors, fiber holders, and the suspension arms of atomic force microscopes. The performance of the V-shaped beam is highly dependent upon its initial out-of-plane deflection. This paper reports on the exploration of the out-of-plane deformation of V-shaped micromachined beams. A finite element model has been established to predict the deformation of a V-shaped micromachined beam. The fabrication and characterization of various shapes of SiO2 V-shaped micromachined beams has been performed to observe the out-of-plane deformation caused by residual stress. With the difference between the analytical and experimental results, an etching process dependent mechanism has been discussed. Thus the design criteria to fabricate a flat V-shaped beam is accomplished.