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This paper presents a pair of trapezoid microcantilever probes with a monolithic micromachined thermocouple for inspecting the electrical and thermal properties of Micro-LED. To meet testing requirements, one of the microcantilevers was designed as a single-layer Ni structure for electrical conduction, while the other one, which consists of n-type poly-Si, SiO₂ and Ni layers, was used for temperature sensing. Both microcantilevers were fabricated by using Si bulk micromachining, thin film deposition, and electroplating processes. Fabrication result shows the length of each probe is about 78 μm and 118 μm, and the thicknesses of the microcantilevers and probe tip are 7.2 μm and 5.5 μm. Experiment results depict that the thermocouple junction between Ni layer and poly-Si achieves a good ohmic contact, and the measured sheet resistances for poly-Si and electroplated Ni are 150 Ω /sq and 0.01 Ω /sq. This suggests that the induced thermoelectric voltage can be generated and detected in response to a temperature difference. Mechanical tests verified that the probes provide an available elastic deflection to guarantee that the probe tips can exactly contact the Micro-LED electrodes, with a low contact force. The thermoelectric characteristics of the device have been further confirmed and calibrated on the basis of the measurement results of a commercial mm-sized LED in cooperation with an infrared camera. For the subject of the Micro-LED chip with a square size of 75 μm, its electrical and thermal properties were successfully determined, as the measured chip temperature is 52 °C at the applied current of 100 μA. [2021-0053]

A 1D MEMS (Micro-Electro-Mechanical Systems) mirror for LiDAR applications, based on vertically asymmetric comb-drive electrostatic actuators, is presented in this work employing a novel fabrication process. This novel micromachining process combines typical SOI-based bulk micromachining and grayscale lithography, enabling the fabrication of combs actuators with asymmetric heights using a single lithography step in the active layer. With this technique, the fabrication process is simplified, and the overall costs are reduced since the number of required lithography steps decrease. The fabricated mirrors present self-aligned electrodes with a 2.8 mu m gap and asymmetric heights of the movable and the fixed electrodes of 20 mu m and 50 mu m, respectively. These asymmetric actuators are an essential feature for the operation mode of this device, enabling both in resonant and static mode operation. A mirror field of view (FOV) of 54 degrees at 838 Hz was achieved under low-pressure, when resonantly operated, and a FOV of 0.8 degrees in the static mode., This work was supported by the European Structural and Investment Funds in the FEDER Component through the Operational Competitiveness and Internationalization Programme (COMPETE 2020) under Project 037902 (POCI-01-0247-FEDER-037902). The work of Carlos Ferreira was supported by the Fundacao para a Ciencia e Tecnologia (FCT) under Grant PD/BDE/135102/2017. Subject Editor M. Rais-Zadeh.

MEMS Safety-and-Arming device is the new generation of S&A device, which integrates the mechanism of actuation and barrier. Fabricated by Micro-Nano processing, its minimized structure and easy integration make it indispensable support to the development of weapon miniaturization, integration and intelligence. Confined by the material and fabrication process, the current MEMS S&A device displays such problems as the tiny output displacement, weak structural strength and low functional integration. In order to solve these technical difficulties, the silicon based MEMS S&A device with metal enhanced structure is proposed in this paper. The process of bulk micromachining and electroplating are integrated together. Based on the SOI substrate, the fabrication of movable structure can be realized. This novel combination equips the device with the qualities of high structural strength and miniaturization. With specific control signal, the MEMS S&A device can generate 1 mm output displacement, and change the device status smoothly (safe to armed, or armed to safe). The micro detonator has been integrated in the system. Stimulated by the surge voltage (1400 V), the flyer can be accelerated to the speed of 1370 m/s. The safety and armed function is validated by the high pressure sensor. The test results show that the metal enhanced layer can stay intact after being stroked by the flyer, and the collision pressure has decreased almost 21.4 times (from 13.5 GPa to 632 MPa). [2019-0184]

Optomechanical SiN nano-oscillators in high-finesse Fabry–Perot cavities can be used to investigate the interaction between mechanical and optical degree of freedom for ultra-sensitive metrology and fundamental quantum mechanical studies. In this paper, we present a nano-oscillator made of a high-stress round-shaped SiN membrane with an integrated on-chip 3-D acoustic shield properly designed to reduce mechanical losses. This oscillator works in the range of 200 kHz to 5 MHz and features a mechanical quality factor of $Q\simeq 10^{7}$ and a Q-frequency product in excess of $6.2 \times 10^{12}$ Hz at room temperature, fulfilling the minimum requirement for quantum ground-state cooling of the oscillator in an optomechanical cavity. The device is obtained by MEMS deep reactive-ion etching (DRIE) bulk micromachining with a two-side silicon processing on a silicon-on-insulator wafer. The microfabrication process is quite flexible such that additional layers could be deposited over the SiN membrane before the DRIE steps, if required for a sensing application. Therefore, such oscillator is a promising candidate for quantum sensing applications in the context of the emerging field of quantum technologies. [2018-0186]

In the microelectromechanical systems (MEMS) field, low-range (e.g., kPa or sub-kPa) differential pressure sensors have remained difficult for decades. Generally, there are two unsolved problems that hinder volume production and wide applications in consumer-electronics. First, high sensitivity required very thin and large sensing diaphragm normally fabricated with low yield, and thus, high selling price. Second, high sensitivity required large deflection of the diaphragm easily causeing severe output of non-linearity that degrades the detecting precision. This paper reports a so-called thin-film under bulk (TUB) MEMS technique to high-yield fabricate high-performance low-range pressure sensors for smart central air-conditioning systems. With the single-wafer-based TUB structure, pressure-induced stress is highly concentrated in a bulk-silicon beam-island structure for piezoresistive readout, where a very thin but uniform poly-silicon diaphragm can be formed beneath the bulk-silicon structure to sustain the pressure. The beam-island reinforced structure brings about decreased deflection and highly linear output. Micro-columns are also formed under the bulk-silicon islands as over-range protection stoppers that are important for low-range pressure sensor. After the description about the 1.2 mm $\times 1.2$ mm tiny-sized sensor-chip design and its single-wafer fabrication process, a test is conducted that results in 22-mV output for 1.2-kPa measure range and very good linearity of ±0.05% (FS). About $100\times $ over-range protection capability of the sensor is also achieved. The novel high-yield TUB process can be used for low-cost production of high-performance pressure sensors for the applications of new-generation smart central air-conditional systems and spirometers, etc, and the bulk/surface combined TUB micromachining technique promises to be widely used for the formation of various complex MEMS structures. [2016-0309]

In this paper, we present the design, fabrication, and characterization of a long-arm comb-drive actuator with an externally mounted large mirror for optical applications. The provision for an externally mounted mirror can be useful for many optical applications, which require large and high-quality reflecting surfaces. The angular stretch of the comb fingers at the far end is kept smaller than those near the anchor point. This structural feature allows the design of actuator arm lengths of over 5 mm. The truss of the actuator is designed carefully to support the large movable arm. An analytical model for the electrostatic forces in the actuator was developed, and detailed analyses for side instability and resonance frequency were performed. The complete fabrication process involving bulk micromachining of silicon-on-insulator (SOI) wafer using a two-mask process is described. A procedure for efficient mounting of the mirror utilizing die bonder, vacuum tip, and silver epoxy is demonstrated. Static characterization measurements show that the actuator can achieve a rotational angle of 3° with an applied voltage of 130 V. A resonance frequency of $\sim 246$ Hz for a mirror size of $2~\textrm {mm} \times 100~\mu \textrm {m} \times 1$ mm was determined by optical characterization; this closely matches with the simulation results and the analytical model. [2014-0318]

This paper presents a micromachined claw probe with electroplating nickel for microsolder ball electrical testing applications. The suspension claw structure consists of two bridges and four curved cantilevers, which have a flexible spring constant in a small region. The out-of-plane claw-probe unit was fabricated using silicon bulk micromachining, titanium deposition, and nickel electroplating processes. The typical bending cantilever structure, made by nickel electroplating, had a thickness of 6.5 μm, a width of 10 μm, and a length of 80 μm. The maximum out-of-plane deflections of the fabricated 40 × 40 claw-probe array were approximately 50 ± 1.2 μm, under the effect of residual tensile stress of 923 MPa. For the probing test of the microsolder ball with a diameter of 200 μm, under the contact force of 1.75 mN, the measured path resistance was about 30 Ω, and the moving stroke of the microsolder ball was 14 μm. The extendable overdrive stroke was over 30 μm, after probe contact with the microsolder ball, and obvious damage was not observed on the surfaces of the claw probe except for several slight scrapes on the sidewall of the microsolder ball. This probe card is potentially capable of providing a very large number of micromachined probes in an array format and can also satisfy the requirements for a fine-pitch ball grid array and low-cost wafer-level testing.

In this paper, we introduce a 2-D microelectromechanical systems scanner for 3.2-mm-diameter dual-axis confocal microendoscopes, fabricated exclusively by front-side processing. Compared to conventional bulk micromachining that incorporates back-side etching, the front-side process is simple and thus enables high device yield. By eliminating the back-side etch window, the process yields compact and robust structures that facilitate handling and packaging. An important component of our front- side fabrication is a low-power deep reactive ion etching (DRIE) process that avoids the heating problems associated with standard DRIE. Reducing the RF etch coil power from 2400 to 1500 W leads to elimination of the spring disconnection problem caused by heat-induced aggressive local etching. In our scanner, the outer frame of the gimbal is split and noncontinuous to allow the scanner to be diced along the very edge of the scanning mirror in order to minimize the chip size (1.8 mm × 1.8 mm). The maximum optical deflection angles in static mode are ±5.5° and ±3.8° for the outer and inner axes, respectively. In dynamic operation, the optical deflection angles are ±11.8° at 1.18 kHz for the outer axis and ±8.8° at 2.76 kHz for the inner axis.

We present a wireless and power-free, optomechanical, implantable microsensor that can potentially be used to accurately monitor intracranial pressure (ICP) over long periods of time. The developed microsensor vertically integrates a glass mini-lens with a two-wavelength quantum dot (QD) micropillar that is photolithographically patterned on an ICP-exposed silicon nitride membrane. The operation principle is based on a novel optomechanical transduction scheme that converts ICP changes into changes in the intensity ratio of the two-wavelength, near-infrared fluorescent light emitted from the QDs. The microsensor is microfabricated using silicon bulk micromachining, and it operates at an ICP clinically relevant pressure dynamic range (0-40 mmHg). The microsensor has a maximum error of less than 15% throughout its dynamic range, and it is extremely photostable. We believe that the proposed microsensor will open up a new direction not only in ICP monitoring but in other pressure-related biomedical applications.

Accepted: 2011-06-17, 資料番号: SA1003111000

A single-side processed dual-cantilever high-shock accelerometer in (111) silicon wafers is proposed in this paper. The device is formed by using advanced silicon surface and bulk micromachining technologies, including deep-reactive ionic etch and lateral under-etching structural release. Because the sensor is fabricated in (111) silicon wafer and has a single-chip single-side structure, it facilitates simple post-packaging, reduced device dimension, and low cost mass production. The controllable gap distance between the bottom surface of the cantilever and the substrate can be used for restraining cross-sensitivity of orthogonal direction. The performance of the accelerometer is examined by using a free dropping hammer system. The results of the shock test show the acceleration sensitivity of 0.71 μVg-1 for a 20 500 g shock acceleration under 3.3 V power supply and the resonant frequency of 79 kHz. The zero-point offset temperature drift of the sensor is 89 within the temperature range of to 120 .

This paper presents an RF microelectromechanical systems (MEMS) switch based on hybrid technology. Electromechanical, microwave, and fabrication design considerations are presented. The methodology is illustrated using shunt contact MEMS switches. The fabrication of the MEMS devices was performed using bulk micromachining processing of a silicon-on-insulator wafer, followed by vertical (3-D) integration with a microwave coplanar transmission line on a GaAs and silicon substrates. The electromechanical and RF performance of the switch were characterized. An isolation of 34 dB at 35 GHz and an insertion loss of 0.1 dB at 35 GHz for a shunt switch were achieved. The concept of a packaged RF switch described in this paper enables a modular implementation of a flexible switch design, independent of the RF circuit substrate material or technology being used.

An accurate alignment of surface-to-bulk features (within ±2 μm) during a double-sided silicon wafer processing can be extremely difficult. This is due to a combination of mask misalignment errors and unreliability of bulk etching techniques in translating the bulk feature shapes down to the surface side. In this paper, we present a fabrication process for an electrostatically actuated cantilever device where an accurate surface-to-bulk feature alignment is imperative to the operation of the device. The fabrication process compensates for the bulk etch-induced feature size variation and mask misalignment errors using a combination of self-aligning features and C4F8 plasma polymer passivation.

This paper presents a 2-DOF silicon-on-insulator (SOI) microelectromechanical systems (MEMS) mirror with sidewall (SW) electrodes. The biaxial MEMS mirror with SW is actuated by electrostatic actuators. The dimension of mirror plate is 1000?m × 1000?m, with a thickness of 35 ?m. The analytical modeling, fabrication process, and performance characteristics are described. This paper analyzes the effects of the three-end single crystal serpentine torsion bar width and the bottom and SW electrodes on the performance of the mirror. A new fabrication process based on SOI wafer, hybrid bulk/surface micromachined technology, and a high-aspect-ratio shadow mask is presented. In comparison to previous fabrication processes and the Optical iMEMS process, the process is novel, easily understood, and simple to realize. The measured maximum angular deflection achieved is ±11°(mechanical angle) at a static operating voltage and is ± 21°(mechanical angle) at resonance frequency driving. This mirror is well suited for applications where these characteristics are critical, such as in confocal or endoscopic scanning elements

In this paper, a silicon bulk micromachined lateral-axis tuning-fork gyroscope (TFG) with a decoupled comb drive and torsional sensing comb capacitors is presented. The novel driving comb capacitors are used to suppress the parasitic out-of-plane electrostatic force and, hence, can decouple the mechanical crosstalk from the sensing mode to the driving mode in a simple manner. The torsional sensing combs are designed to differentially sense the out-of-plane rotational moment and are arranged centroidally to be immune to fabrication imperfections for good linearity and electrostatic force balancing. The torsional sensing combs adopted in the TFG help to lower the air damping of the sensing mode while the driving mode of the gyroscope is dominated by slide-film air damping; hence, it can work even at atmospheric pressure. The process for this lateral-axis gyroscope can also be used to fabricate z-axis gyroscopes; therefore, low-cost miniature monolithic inertial measurement units can be realized without vacuum packaging. The TFG is tested at atmospheric pressure with a sensitivity of 17.8 mV/°/s and a nonlinearity of 0.6% in a full-scale range of 1000°/s. The bias stability is measured to be 0.05°/s (1 ?) in 30 min with an equivalent noise angular rate of 0.02°/s/Hz1/2.

This paper describes a bulk-micromachined electrostatically tunable Fabry-Perot interferometric filter. The device is a hybrid optical filter combining fiber optics and microelectromechanical systems (MEMS) technologies. The static mirror is a Bragg grating mirror built on the end face of an optical fiber that is integrated with a MEMS device, which includes the tunable gold-coated mirror. The MEMS device is fabricated in ?100?-oriented silicon wafers using modified and optimized batch MEMS processes. A two-stage approach was used to achieve high finesse (F) and broad tunability simultaneously. In the first stage, actuator issues and mirror structural defects were corrected for by optimizing the fabrication-process parameters. In this stage, near-theoretical performance has been achieved with a pure Si MEMS tunable etalon. In stage two, optical fibers with dielectric stack mirrors from Micron Optics, Inc. have been integrated with the MEMS devices to form tunable cavities. The device insertion loss was below 15 dB and was mostly attributed to absorption losses in the gold coating. We measured a pass bandwidth of around 0.54 nm and a tuning range of nearly 120 nm resulting in an F of over 220.

We report a dual-color total-internal-reflection (TIR)-based chip that can generate two overlapping evanescent fields with different wavelengths for simultaneous imaging of two types of fluorophores. We derived a general relationship among the dimensions of the components of the chip to guarantee the overlap of two evanescent fields. Optical simulation results also confirm the generation and overlap of two evanescent fields. Using Si bulk micromachining and poly(dimethylsiloxane) (PDMS) casting, our fabrication method integrates all miniaturized optical components into one monolithic PDMS chip. Thus, assembly is unnecessary, and misalignment is avoided. Our PDMS chip can be employed with various sample delivery platforms, such as glass slide, flow cell, microchannel, etc. We first demonstrated the capability of the chip by imaging TIR fluorescent spots of a mixture of two fluorophores, namely, fluorescein and tetramethylrhodamine. We then employed the chip to observe the Brownian motion of a mixture of nile-red and dragon-green 500-nm microbeads. Our chip could potentially be integrated into a micro-total analysis system for highly sensitive and high-resolution dual-fluorescence imaging applications.

This paper presents the design, optimization, fabrication, and test results of an electrothermally actuated tip-tilt-piston micromirror with a large optical aperture of 1 mm. The fabrication of the device is a combination of thin-film surface micromachining and bulk silicon micromachining based on silicon-on-insulator wafers. The device has 3-DOF of actuations, including rotations around two axes in the mirror plane, and out-of-plane piston actuation. The micromirror shows an optical scan range of plusmn30deg about both x- and y-axes and displaces 480 mum in the z-axis, all at dc voltages that are less than 8 V. Dynamic testing of the micromirror shows that the thermal response time of each actuator is about 10 ms. Resonant frequencies of the piston and rotation motion are 336 and 488 Hz, respectively. The unique structural design of the device ensures that there is no lateral shift for the piston motion and no rotation-axis shift for the rotation scanning. With the large tip-tilt-piston scan ranges and low driving voltage, this type of device is very suitable for biomedical imaging and laser beam steering applications.

A simple and new technique for interlayer electrical interconnection for silicon-on-insulator microelectromechanical systems (SOI-MEMS) micromachining was developed without using additional device layers or patterning processes. A part of the SOI microstructure was shaped into a slender cantilever and intentionally brought into contact onto the substrate surface by surface stiction force after sacrificial release. The contact resistance between the stiction bar and the substrate was studied with and without a subsequent metallization process. The stiction bar was found to improve the MEMS design flexibility in allocating electrical components (comb-drive electrodes and interconnection tethers) and mechanical components (suspensions and frame) to the SOI and the substrate layer and to make a high-density complex double-deck structure in a small footprint. As an example of the high-density design, we developed a micro-XYZ stage with the lateral and vertical comb-drive mechanisms and compared the design with the conventional bulk micromachined structures.

A small-signal model that describes the energy exchange between surface micromachined beams and bulk-lead zirconium titanate (PZT) actuators attached to the silicon substrate is presented. The model includes detection of acoustic waves launched from electrostatically actuated structures on the surface of the die, as well as their actuation by bulk waves generated by piezoelectric ceramics. The interaction is modeled via an empirical equivalent circuit, which is substantiated by experiments designed to extract the model parameters. The equivalent model is valid for cases where the beam resonance frequency is much smaller than the thickness mode resonance of the PZT/silicon stack. In this paper, the resonance frequency of the beams ranges between 200 and 300 kHz. As energy transfer between bulk-PZT and electrostatic actuated beam resonators must be reciprocal for small signals, this paper uses the extracted equivalent model to describe the physical sources of error that account for discrepancies in reciprocity.

A thin-film electrode array with integrated position sensors has been developed for a cochlear prosthesis. The array is designed to minimize tissue damage during array insertion and achieve deep implants that hug the modiolus inside the cochlea. The array is fabricated using bulk micromachining technology and contains embedded polysilicon piezoresistive sensors for wall-contact detection and array-shape recognition. Nine strain gauges are distributed at the tip and along the array, covering the 8-mm-long shank. Each sensor is arranged in a half Wheatstone bridge whose output signal is time multiplexed, amplified (10 or 30 times), and band limited. The equivalent gauge factors are typically about 15, permitting array-tip position to be determined within a 50-mum resolution while providing wall-contact output signals of more than 50 mV at the tip. The arrays use a parylene-silicon-dielectric-electrode structure, improving flexibility while maintaining enough robustness to facilitate a modiolus-hugging shape defined by a polymeric backing device. Integrated with an articulated position-control device, such arrays are the first step toward providing closed-loop control of array insertion and improved perception of speech and music.

This paper presents the design, fabrication, and measurement results for a novel non-contact-type radio-frequency (RF) microelectromechanical systems switch for 24-GHz radar applications. The proposed switches are free from unavoidable microwelding and stiction problems in other contact types, which in turn guarantee high reliability and long lifetime. The developed switch is a capacitive shunt type using a variation of the capacitance between the signal line and ground lines. The capacitance is precisely regulated by comb-drive actuators. This concept is simple, but the design requires a large and precise mechanical motion. In addition, for a low-loss switch structure, an air bridge with a large air gap is required. Therefore, the selective silicon-on-insulator process, based on the sacrificial bulk micromachining process, is designed for this switch fabrication. First, large insulating supports are fabricated 60 ?m below the wafer surface, and then, the RF switch is fabricated on these insulating supports. The measured actuation voltage is 25 V, and the actuation stroke is 25 ?m. The switching times are 8 ms in the off to the on state and 200 ?s in the on to the off state. In the RF characteristic measurements, the insertion loss without the long coplanar waveguide line loss is 0.29 dB and the isolation is 30.1 dB at 24 GHz. The bandwidth is relatively narrow, and the isolation is 25 dB or better in the range of 23.5-29 GHz. The reliability test for the switch was performed 109 times with 18-mW RF power. We observed no mechanical failure or RF performance degradation. A power handling capacity of 0.9 W with a hot-switch condition was achieved.

A microelectromechanical system device fabricated by deep reactive ion etching for friction characterization was developed with single-crystal silicon in this paper. Two orthogonally placed electrostatic comb-drive actuators were adopted to apply the normal load and generate the tangential motion. A sensing plate for sliding contact and a driving plate with two bumps designed for the Hertzian contact are included in the testing device. With an image processing technique developed, experimental displacement data were extracted from the captured video frames. A quasi-static stick-slip model was developed to predict the transitions between static and kinetic friction at the contacting sidewall surfaces. Both static and kinetic friction coefficients can be determined by using this model, and these measured results are shown to be insensitive to errors in the calculation of the electrostatic forces. The measured displacements of the driving and sensing plates are in good agreement with the trend predicted by the model. Based on the Hertz theory, the contact silicon interface has been found to be in an elastic regime at the scale of the designed bumps. With the aid of the quasi-static stick-slip model, a saturation phenomenon of the kinetic friction at the sidewall surfaces was observed while the normal load was increased.

This paper presents the design and fabrication of a single-layer out-of-plane thermal actuator. The step-bridge structure design enables bending and then buckling of the actuator in the out-of-plane direction by Joule heating. Moreover, the moving direction of the actuator can be specified by the step structure. In summary, the step-bridge actuator design has the following five merits: (1) The load-deflection relation is easily tuned; (2) the bistable buckling behavior is prevented; (3) the unwanted vibration modes can be suppressed; (4) the delamination problem is prevented; and (5) the bridge structure is stiffer and more stable. The actuator and its application on a lens positioning stage have been implemented using p++ Si layer by bulk micromachining. It demonstrates that a typical actuator would move upward with an amplitude near 13 mum when driven at 54 mW.

The paper deals with the new 3D structures fabricated by the bulk micromachining of (110), (112), and (522) silicon substrates. The structures employ a specific arrangement of {111} planes on these substrates and are entirely bounded by these slowly etching planes. Design rules and complete structures of new seismic-mass systems, suspended on two or four beams, composed of the {111} planes, are presented. The beams supporting the masses are inclined toward the substrate at different angles, which can be adjusted by an appropriate selection of crystallographic orientation of the etched substrate. The structures seem to be interesting as structural components of multiaxes accelerometers. Slanted membranes fabricated by the double-sided etching of (112) and (552) substrates have also been presented. The structures utilize the {111} planes, inclined at a low angle toward the etched substrate, both as structural elements, as well as a natural etch stop. It can be claimed that the application of Si substrates with unconventional crystallographic orientations opens new possibilities in the micromachining of 3D structures.

This paper reports on novel coilless microscanning mirrors driven by the magnetostatic force that resulted from a magnetic interaction as well as the Lorentz force that is induced by an eddy current. This eliminates complicated coil routing and insulation layer deposition and simplifies fabrication allowing easy integration with micromachining and complementary metal-oxide-semiconductor processes. Bulk micromachined one-axis and two-axis scanning mirrors are demonstrated, displaying 1-D and 2-D scanning patterns. Two-dimensional scanning patterns are easily tuned by varying the combination of driving frequencies. The results show that the diamagnetic (Cu) mirror is mainly driven by the eddy-current-induced Lorentz force, whereas the ferromagnetic (Ni) mirror is mainly driven by the magnetostatic force.

Microneedle-based drug delivery has shown considerable promise for enabling painless transdermal and hypodermal delivery of conventional and novel therapies. However, this promise has yet to be fully realized due in large part to the limitations imposed by the micromechanical properties of the material systems being used. In this paper, we demonstrate titanium-based microneedle devices developed to address these limitations. Microneedle arrays with in-plane orientation are fabricated using recently developed high-aspect-ratio titanium bulk micromachining and multilayer lamination techniques. These devices include embedded microfluidic networks for the active delivery and/or extraction of fluids. Data from quantitative and qualitative characterization of the fluidic and mechanical performance of the devices are presented and shown to be in good agreement with finite-element simulations. The results demonstrate the potential of titanium micromachining for the fabrication of robust, reliable, and low-cost microneedle devices for drug delivery

Multimaterial, microelectromechanical systems-based cantilever probes were developed for high-frequency magnetic field imaging. The basic configuration of the probe consists of a cantilever beam fabricated using surface micromachining and bulk micromachining techniques with dielectric silicon nitride and silicon oxide materials on a silicon wafer. A gold patterned metallization at the tip of the cantilever provides a source of eddy current heating due to the perpendicular component of the high-frequency magnetic field. This thermally absorbed power is converted to mechanical deflection by a multimaterial trilayer cantilever system. The deflection is measured with a beam-bounce optical technique employed in atomic force microscopy systems. We discuss the modeling, design, fabrication, and characterization of these field imaging probes

A novel piezoresistive scheme is proposed to solve the problem of piezoresistive gyros in terms of low-sensitivity and high-temperature drift. Based on the piezoresistive scheme, a micromachined vibratory gyroscope is developed. By using axially stressed piezoresistive tiny-beams, piezoresistive detection to Coriolis-acceleration can be realized with both high sensitivity and high resonant frequency, i.e., high gyro operation frequency. Thanks to the high piezoresistive sensitivity, precise frequency matching between the driving and detecting modes is unnecessary. Another four-terminal transverse piezoresistive element is used to monitor and stabilize the amplitude of the seesaw-like torsional vibration through a feedback loop. With the same feedback loop, temperature drift of the piezoresistive angular-rate sensing signal can be on-chip compensated, as the transverse piezoresistance tracks the temperature drift of the angular-rate sensing piezoresistors. The gyro is designed and fabricated by bulk micromachining. Measurement results verify the proposed piezoresistive gyro scheme and show noise-limited angular-rate resolution of 0.33deg/s for plusmn300deg/s range. Considering the mature fabrication technology and simple signal-readout for piezoresistive sensors, the piezoresistive microgyros are promising for low-cost applications

This paper describes a proof-of-concept deformable mirror (DM) technology, with a continuous single-crystal silicon membrane reflecting surface, based on PbZr0.52Ti0.48O3 (PZT) unimorph membrane microactuators. A potential application for a terrestrial planet finder adaptive nuller is also discussed. The DM comprises a continuous, large-aperture, silicon membrane "transferred" onto a 20times20 piezoelectric unimorph actuator array. The actuator array was prepared on an electroded silicon substrate using chemical-solution-deposited 2-mum-thick PZT films working in a d31 mode. The substrate was subsequently bulk-micromachined to create membrane structures with residual silicon acting as the passive layer in the actuator structure. A mathematical model simulated the membrane microactuator performance and aided in the optimization of membrane thicknesses and electrode geometries. Excellent agreement was obtained between the model and the experimental results. The resulting piezoelectric unimorph actuators with patterned PZT films produced large strokes at low voltages. A PZT unimorph actuator, 2.5 mm in diameter with optimized PZT/silicon thickness and design showed a deflection of 5.7 mum at 20 V. A DM structure with a 20-mum-thick silicon membrane mirror (50 mm times50 mm area) supported by 400 PZT unimorph actuators was successfully fabricated and optically characterized. The measured maximum mirror deflection at 30 V was approximately 1 mum. An assembled DM showed an operating frequency bandwidth of 30 kHz and an influence function of approximately 30%

For many micromachined sensors such as microphones and accelerometers, optical displacement sensing may have advantages over capacitive sensing-offering potentially high-displacement sensitivity independent of sensor area and gap height. A particular diffraction-based optical displacement sensor design consisting of a sensing diaphragm suspended over a rigid grated electrode has demonstrated advantages in terms of sensitivity, integration and stability. When illuminated from the backside, this structure generates a zeroth and complementary higher order diffracted beams whose intensities are modulated by the diaphragm displacement with the sensitivity of a regular Michelson interferometer. In previous work, acoustic devices surface micromachined on quartz substrates using aluminum for the diaphragm and grating were presented and characterized. In this work, we present the fabrication and characterization of a surface- and bulk-silicon micromachined diffraction-based optical microphone structure fabricated with Sandia National Laboratories' SwIFT-Litetrade process, which uses silicon nitride and polysilicon structural materials that have been employed extensively in MEMS and form a more thermally matched material set robust against corrosion and fatigue. The process introduces a new design space to microscale optical displacement sensing, enabling large, soft structures with perforated back-plates ideal for microphone and inertial-sensor designs

This paper demonstrates a technique to premold and transfer lead-free solder balls for microelectrocmechanical systems (MEMS)/electronics packaging applications. A reusable bulk micromachined silicon wafer is used to mold a solder paste and remove excess flux prior to transfer to a host wafer that may contain released MEMS. This technique has been used to fabricate low temperature thin film MEMS vacuum packages. Long term (>5 months) reliability of these packages at room temperature and pressure is demonstrated through integrated Pirani gauges. These packages have survived over 600 hours in an autoclave (130degC, 85% RH, 2 atm) and more than 1300 temperature cycles (55degC to 125degC)

This paper describes the design, fabrication, and characterization of the first MEMS piezoelectric tunable capacitors employing zinc oxide (ZnO) actuation. Relatively simple design rules for the device-structure optimization for largest deflection are shown from simulation results based on theoretical equations. The ZnO-actuated tunable capacitors are accordingly designed and fabricated with both surface and bulk micromachining techniques. Through the surface micromachining process, sacrificial silicon is removed with XeF2, and parylene is successfully used as a supporting layer for a piezoelectric unimorph cantilever. For comparison, other two different structures using plasma-enhanced chemical-vapor deposition (PECVD) SiN and SU-8 as supporting layers are also fabricated. Deflection analyses are performed for three specific structures, among which the parylene-supported one is demonstrated to have the largest displacement and most suitable for tunable capacitor application. For bulk-micromachined tunable capacitor, we have implemented a novel design of a large structure driven by a ZnO unimorph, and obtained a tuning ratio of more than 21:1 (0.46 pF-10.02 pF). This is the highest tuning ratio reported to date for parallel-plate tunable capacitors while requiring an applied voltage of only 35 V

The design and fabrication of a novel microfluidic nanoprobe system are presented. The nanoprobe consists of cantilevered ultrasharp volcano-like tips, with microfluidic capabilities consisting of microchannels connected to an on-chip reservoir. The chip possesses additional connection capabilities to a remote reservoir. The fabrication uses standard surface micromachining techniques and materials. Bulk micromachining is employed for chip release. The microchannels are fabricated in silicon nitride by a new methodology, based on edge underetching of a sacrificial layer, bird's beak oxidation for mechanically closing the edges, and deposition of a sealing layer. The design and integration of various elements of the system and their fabrication are discussed. The system is conceived mainly to work as a "nanofountain pen", i.e., a continuously writing upgrade of the dip-pen nanolithography approach. Moreover, the new chip shows a much larger applicability area in fields such as electrochemical nanoprobes, nanoprobe-based etching, build-up tools for nanofabrication, or a probe for materials interactive analysis. Preliminary tests for writing and imaging with the new device were performed. These tests illustrate the capabilities of the new device and demonstrate possible directions for improvement.

In this paper, we present the design, fabrication, and measurements of a two-dimensional (2-D) optical scanner with electrostatic angular vertical comb (AVC) actuators. The scanner is realized by combining a foundry-based surface-micromachining process (Multi-User MEMS Processes-MUMPs) with a three-mask deep-reactive ion-etching (DRIE) postfabrication process. The surface-micromachining provides versatile mechanical design and electrical interconnect while the bulk micromachining offers high-aspect ratio structures leading to flat mirrors and high-force, large-displacement actuators. The scanner achieves dc mechanical scanning ranges of /spl plusmn/6.2/spl deg/ (at 55 Vdc) and /spl plusmn/4.1/spl deg/ (at 50 Vdc) for the inner and outer gimbals, respectively. The resonant frequencies are 315 and 144 Hz for the inner and the outer axes, respectively. The 1-mm-diameter mirror has a radius of curvature of over 50 cm. [1454].