MEMS offer ultra-low mass, low-power components which may integrated into a variety of aerospace systems. Aerospace-specific MEMS are limited by the relatively small size of the aerospace vehicle market compared to traditional MEMS markets such as automobiles and home computers. Nevertheless, significant applications such as inertial guidance, micro-vehicle propulsion, and active antennas will drive evolution of existing MEMS technologies to meet these needs. MEMS enable many near-term micro-vehicle concepts, and possible mid-to-far term applications such as aerodynamic skin flow control and active aerospace structures.

This paper describes design, fabrication and characterization of a proof-of-concept vertical travel linear microactuator designed to provide out-of-plane actuation for high precision positioning applications in space. The microactuator is designed to achieve vertical actuation travel by incorporating compliant beam structures within a SOI (Silicon on Insulator) wafer. Device structure except for the piezoelectric actuator is fabricated on the SOI wafer using Deep Reactive Ion Etch (DRIE) process. Incremental travel distance of the piezoelectric actuator is adjustable at nanometer level by controlling voltage. Bistable beam geometry is employed to minimize initial gaps between electrodes. The footprint of an actuator is approximately 2 mm x 4 mm. Actuation is characterized with LabVIEW-based test bed. Actuation voltage sequence is generated by the LabVIEW controlled power relays. Vertical actuation in the range of 500 nm over 10-cycle was observed using WYKO RST Plus Optical Profiler.

This paper describes the results of our demonstration on a proof-of-concept piezoelectric unimorph-based deformable mirror (DM) with continuous single-crystal silicon membrane. A PZT unimorph actuator of 2.5 mm in diameter with optimized PZT/Si thickness and design showed a deflection of 5 μm at 50 V. DMs consisting of 10 μm thick single-crystal silicon membranes supported by 4×4 actuator arrays were fabricated and optically characterized. An assembled DM showed a stroke of 2.5 μm at 50 V with a resonant frequency of 42 kHz and influence function of approximately 25%.

Adaptive optics techniques have been proved in both laboratory and field tests to the satisfaction especially of the astronomical and surveillance communities. Such success have sparked interests in other fields, however, to increase efficiency and lower costs new technologies have to be brought to fruition. MEMs are becoming a very important player in this arena. In this paper we describe a portable adaptive optics (AO) system that has been tested in both laboratory and field experiments. Results of these tests will be discussed. Capabilities and shortcomings of this technology will be discussed. A look at future applications and trends will be given.

In most adaptive optics systems, there are two elements that control wavefront correction. These are a tip/tilt platform and a deformable mirror. The tip/tilt platform can correct the lower order aberrations like piston, tip and tilt. The deformable mirror can correct the higher order aberrations like defocus, coma, spherical, etc. Currently in this method, two conjugate planes must be created by the two elements. It is also a necessity that these two conjugate planes be identical. This requires more optics and a more complicated alignment process. In this project a deformable mirror is mounted onto a tip/tilt platform resulting in the two correction elements having the same conjugate plane, automatically. This is made possible by the use of a lightweight deformable mirror, as traditional deformable mirrors tend to be quite large and bulky. Results of this experimental project will be presented.

This paper analyzes the current status of the MEMS industry. After the 2000 and 2001 years with high expectation for MEMS devices for the optical telecommunications, followed by the 2002/2003 downturn leading to the closing of more than 100 MEMS fabs worldwide, this industry has come back to a more normal way of working. There are still 10 to 15 companies worldwide which will certainly end their business within 16 months but the overall activity is more stabilized. MEMS markets will reach 5.4 B$ in 2005, with growth rates which are very different if one compares different market segments. The top 30 MEMS manufacturers have a market share of more than 60% of the total market; the remaining 40% is shared by more than 200 companies. Most of the smallest companies have 2 business models: either small companies developing specific processes, with R&D and small volume production, or systems manufacturers with integrated fabs. These fabs are loaded at less than 40% but considered as an enabler for the system business. Many changes are currently appearing: as contract manufacturers become more credible, system manufacturers are looking to externalise their fabrication processes; fabless companies are also finding companies able to produce at the right cost and quality. The fabless business model is now well structured.

Microsystems for Radio Frequency applications, known as RF MEMS, have entered the commercialization phase in 2003. Bulk Acoustic Wave filters are already produced in series and first commercial samples of switches are available. On the other hand, reliability and packaging problems are still a major hurdle especially for switches and tunable capacitors. Will RF MEMS hold their promise to be one of the future major businesses for MEMS? The presentation will give an overview on RF MEMS applications and market players. WTC will highlight technical challenges that still have to be solved to open mass markets such as mobile telephony and WLAN. WTC will also present applications of RF MEMS and opportunities in niche markets with high added value like military and space applications. WTC will provide a regional analysis and compare R&D focus and public funding situation in North America, Europe and Asia. Finally, WTC will present an updated product roadmap market forecast for RF MEMS devices for the 2004-2008 time period.

MEMS technology is presented as a promising technology to realize high Q variable capacitors and RF switches with high performance and with high levels of integration. These devices are key elements for systems like phase shifters, tunable filters and matching networks. However, the reliability and the yield of the RF MEMS devices remain the key limiting factors holding the MEMS technology from spreading in the industrial applications. From a RF designer's point of view, reliability and yield are closely related to the accuracy of the definition of the up- and down-state capacitances of the devices. In this paper, we propose a novel compact series capacitive structure with improved predictability and RF performance. The new design mimics a clamped-clamped bridge to lower its sensitivity to the process-induced stress gradient in the up-state. The shape of the device and its consequent parameters, e.g. up- and down-capacitances, are thus more accurately defined even in presence of non-ideal clamping conditions. Unlike the series switchable capacitors with transverse restraining bridge, the novel device does not suffer from high frequency parasitic resonances. Finally, the novel device implements the floating top metal. This allows accurately defining the down-state capacitance of the design at will. Boosted series capacitive switches with inline-restrained cantilever beams have been realized and measured. The isolation is better than 20dB until 1GHz without optimization. The insertion loss in the down-state is better than 0.2dB in the range 1-20GHz. It further slowly and continuously decays to reach 0.4dB at 40GHz without any resonances.

This paper describes new type of MEMS spiral inductor using benzocyclobutene (BCB) for wireless applications. BCB consists of several attractive features for on-chip RF inductors, i.e., high resistivity, low dielectric constant and lower curing temperature. The fabricated inductor coils had 2.5 turns with 20μm for width, 20μm for pitch and the thickness of 2μm. The inductor coils are suspended about 12μm from the bottom BCB substrate. Our measured quality factor was 19 at 3.1GHz frequency. The measured inductance was approximately 3nH and it remained constant up to 10 GHz. The self resonant frequency (SRF) was at 13.6GHz.

We report on experimental work that characterizes the frequency response of resonators of Microfabricated Acoustic Spectrum Analyzer (MASA) devices which were fabricated using Sandia's SUMMiT processing technology. A 1.1 micron silicon nitride layer was used in the fabrication to isolate the sense mechanism from the actuation mechanism. The devices are actuated using electrostatic vertical comb-drive actuation in a 30-50 mTorr vacuum and the frequency response is measured using a piezo-resistive readout mechanism. Two MASA devices are tested using comb-drive ac signals (e.g., 200mV) superimposed on a dc bias (e.g., 15V). In addition, dc bias voltages placed on the comb-drive are shown to tune the resonant frequency of the resonator. The frequency response of the piezo-resistive readout mechanism is measured using a 10V dc supply voltage supplied across its Wheatstone bridge. The results show that the piezo-resistive readout mechanism can detect resonant behavior and determine resonant frequency. A laser doppler vibrometer is used as an independent means to characterize the frequency response and verify the results.

Optical Telecommunications bandwidth, spurred by the growth of the internet, experienced unprecedented growth in the late 1990's. The creation of new enterprises was vast and the expansion of established component, system and services companies was also breathtaking. This period of speculative growth was followed in 2001-2004 by one of the most significant market crashes in history. While $20B of venture capital was invested in optical telecom in the last 10 years, the vast majority of that has been written off in the last 4. Countless start-ups inaugurated with great fanfare at the end of the 20th century were unceremoniously shut down at the start of the 21st century.(1) As in all speculative bubbles innovative technologies were born and were buried. Nonetheless, new capabilities emerge from the chaos and disruption; one such example is the advent of Optical MEMS (MOEMS). Its development was vigorously pursued in both academic and corporate laboratories during the boom and, in the author's view; MOEMS constitutes a powerful and versatile tool set that will be an invaluable residual of the last few years. In Telecommunications, MOEMS have been proven to be the technology of choice for many optical switching and wavelength management applications.(2) Variable Optical Attenuators (VOA), Wavelength Blockers (WB), Dynamic Gain Equalizers (DGE), and most recently Wavelength Selective Switches (WSS) are being used in the numerous recent network deployments. Moreover, agile networks of the future will have MOEMS at every node. This presentation will provide an overview of the history of MOEMS in Telecommunications, discuss their byproducts and project the future of the technology.

This paper would propose the design and fabrication methodology of micro mirror for MOEMS devices by CMOS-MEMS common process of CIC, Taiwan. The outstanding features of CMOS-MEMS are mass production, low connections, high precision and easy to combine the circuit with low noise. A {2X3} opposite type Micro Array Thermal Actuator, MATA, is applied to drive the micro mirror for rotation. Such MOEMS would be as a high precision micro positioning device applied on the micro fabrication equipment. A novel elevating structure for the lift of micro mirror is proposed. Warped suspension beam is originally applied on elevating a micro mirror in this work. A modified elevating structure is proposed to improve the lift of micro mirror from 1.1 μm to 14 μm compared to original design. There are three parameters, width, length of the modified elevating structure and the number of single thermal actuators of parallel type MATA, for the performance simulation. The effects of operation voltage varied with three parameters on the displacement of Z axis direction are investigated. The optimum dimension of width, length of modified elevating structure and numbers of single thermal actuator are 10 μm, 240 μm and {1x4} MATA, respectively. Finally, comparisons of mask configuration and real part of finished devices are discussed by SEM photos. The surface quality of micro mirror is almost perfect and the material of micro mirror is aluminum.

A novel microelectromechanical grating with both pitch and blaze angle tuning functions has been designed, simulated, and fabricated and is reported in this paper. This grating device could change spectrum angle through adjusting grating pitch and make reflection match with a particular diffraction order by the blaze angle tuning. This grating could have better dispersion efficiency than most previous tunable gratings because of its small grating pitch. Besides, the reflective surfaces of our MEMS grating are constructed by surface-micromachining aluminum to get high reflective efficiency. For wide tuning range, this grating uses bulk actuators to provide large displacement of about 70um for tuning more than 1/10 of original pitch length. All tuning functions are operated by electrostatic force with a driving voltage below 120V.

In this paper, a novel spatial light modulator is presented. A pixel of the novel spatial modulator is turned fully OFF when all pixel ribbons form a flat reflective plane and turned ON by electrostatically deflecting alternate ribbons to produce a blazed diffraction grating. According to scalar diffraction theory, the optical performance is analyzed in details. And the influence factors on diffractive efficiency are discussed. Meanwhile, with the application of electromagnetics, electrodynamics analysis is introduced including the relation between threshold voltage and structure material characteristic. Computer simulation on the condition of different incidence light, different duty-cycle is carried on, presenting the relation between diffraction efficiency and wavelength, duty-cycle, etc. There is a promising foreground based on optimization of structure.

Electrostatic micromirrors are yet a well-known topic in the world of MOEMS. But in some specific cases, the mirror dimensions should have to be extended in order to be able to switch beams of a larger diameter. In other words, the convergence in dimensions between electronic technologies and classical machining in the range of hundreds microns to millimetre was not yet explored. This is the context of our study, whose goal is to make digital switching devices with a size of some millimetres and a large, pre-fixed deflection angle of ten degrees.

The paper deals with a novel setup of a Hadamard transform spectrometer (HTS) which encoding mask is realized by a micro mirror array. In contrast to other applications of an HTS the mirrors of the array are not statically switched but dynamically driven to oscillate at the same frequency. The Hadamard transform is obtained by shifting the phase shift of oscillation. The paper gives a brief introduction in the entity of the Hadamard transform technique. The driving and detection circuits are presented and first measurement results are discussed.

We proposed a discrete microactuator enabling a nonlinear displacement with respect to digital input by employing electrostatic comb electrodes of curved shape. The comb electrodes were designed to implement a linearization in variable optical attenuator (VOA) with a constant step of 0.5 dB. The experimental insertion loss (IL) was 1.1 dB and attenuation range was 32.6 dB with 4.2% in linearity.

This paper describes a novel method to microfabricate out-of-plane convex and concave microlens array with optical axis parallel to the substrate for free-space optics. With wavelength selection and carefully controlled exposure dosage and development in the SU-8 lithography process, the satisfactory surface profiles and uniformity of pixels on the out-of-plane microlens array are obtained. With the optical axis of each pixel parallel with the substrate, these microlens arrays can be we can prealigned with other optical components, such as lens, prism, or mirror, in the mask design. This out-of-plane polymer microlens array can be pre-aligned with other optical components with no additional adjustment and assembly required, and therefore dramatically reduce the running cost and improve the quality and performance of the integrated optical system. Some preliminary results on pre-aligned fiber couplers and fiber bundle couplers fabricated with this out-of-plane microlens array are also presented.

Four different approaches for the construction of a single crystal silicon vibratory ring gyroscope were investigated. All of them require deep trench etching (DRIE)of silicon, anodic bonding of silicon structures to a glass wafer, and a dissolve silicon wafer process. In the first approach, regular single crystal silicon was used as the starting sensor structural material. Heavy boron diffused silicon (B⁺⁺Si) was formed followed by anodic bonding to the glass plate. The undoped silicon was then dissolved and the device structure was fabricated by deep trench etching of the B++Si. Due to the slow boron diffusion process, this approach severely limits the attainable thickness of the device structure. In the second approach, deep trench etching was carried out first followed by boron diffusion. In order to reduce RIE lag and boron diffusion time, the larger features were subdivided into smaller ones before DRIE process. We found that RIE lag still existed which had a detrimental effect on the sensor performance. In the third approach, silicon-on-insulator (SOI) wafer was used and the sensor structures were built in the Si-epi layer by DRIE. Because of the very slow etch rate of SiO₂ in the DRIE process, RIE lag can be avoided. However, the associated footing problem makes the device dimensional control difficult. In the fourth approach, a layer of epi-GeB⁺⁺Si on silicon wafer was used to build the sensor structures. The fabrication process was similar to that used in the third approach. Both RIE lag and footing problems were avoided. In the operation of the vibratory ring gyroscope, it is highly desirable of having the resonant frequencies around the ring to be isotropic. In this work, theoretical and experimental studies were conducted aiming at achieving the isotropy of the resonant frequency of the single crystal silicon ring, which has an orientation dependent modulus of elasticity. We found that for odd flexural vibration modes, the resonant frequencies of the ring were isotropic, whereas, for even modes they became anisotropic.

Thermal actuators based upon the principle of the thermal expansion have been utilized in various fields in the last decade. The outstanding features of a thermal actuator include simple fabrication process, large displacement, which is in proportion to temperature, and rather low operation frequency. In order to gain more insight into the actuation behavior of Micro Array Thermal Actuator, MATA, applied in MEMS, based on electrical analysis. There are two kinds of MATA, {2x4} opposite type, {1x4} parallel type compared with a single thermal actuator on the electrical analysis for each equivalent circuit, respectively. The investigation analyzed based upon basic theory and advanced computer simulation by a commercial software. The effects of operation voltage and connection length on the variations of displacement and current density of each device are studied in this work. MATA is an actuation device with a highly symmetry electrical loop through the equivalent circuit analysis. There is no current in the connection region of MATA. The phenomenon is supported by the simulation results. There is small current density, which is below 10^-9A/μm², in the connection region. Hence, the performance of MATA is strongly dominated by the geometry of a single thermal actuator, and less dependent on the type and connection number of MATA.

Micromachined cantilevers used as force probes in atomic force microscopy are extremely sensitive to a variety of environment factors such as acoustic noise, temperature and humidity. This unwanted interference can be exploited to produce highly sensitive systems with proper design and under precise conditions. In this paper, we report the development of a new generic process for the fabrication of a microprobe with integrated piezoresistive read-out and built-in piezoelectric actuators. The mechanical performance of cantilever probes of various dimensions was studied. The result from the Finite Element Analysis (FEA) was compared to the experimental results. Application of this probe in a nondestructive, general-purpose, near-field nanomechanical imaging system will be discussed.

Techniques for fabricating high-aspect-ratio microscale structures (HARMS) are being investigated for wide-ranging applications. Microdevices employing metal-based HARMS are of particular interest for mechanical, electro-mechanical, and chemical applications. In many applications, HARMS with two or several distinct heights are necessary, the fabrication of which necessitates two-level or multi-level mold inserts. In addition, tapered mold inserts would help achieving easy insert-part separation. Here we report a process for fabricating two-level, tapered mold inserts by combining UV-lithography on SU-8 resist, one-step metal electrodeposition, polish and level, and SU-8 resist removal. Without tilt and rotation during the lithography process, tapered SU-8 plating molds are obtained by employing light diffraction during lithography and proper development procedures. The SU-8 resist removal process does not reduce its strength. Efficacy of this approach is demonstrated with a two-level insert prototype suitable for fabricating micro heat exchanger parts by compression micromolding.

The ability to monitor shock level is important for missile health monitoring to predict the performance after storage and eliminate potentially damaged units. Shock sensing is also of interest for monitoring the handling conditions of fragile shipments and providing a measure of unit-level quality control not currently available. A MEMS bi-polar single axis latching shock sensor has been developed with the goal of monitoring shock events and with the potential to "wake up" other sensing circuitry after a shock event occurs. An important feature of the sensor is that power is only consumed when a shock event occurs, making it suitable for long-term remote monitoring applications. The shock sensor has been designed, fabricated and characterized. High volume, low unit cost production will be enabled through the use of standard MEMS fabrication technologies such as DRIE and SOI wafer processing.

Compact robust hydraulic actuators are very important for space related applications because of their capability of producing much larger forces per unite volume/mass than existing technologies. The major components of these actuators are PZT stacks (pusher) and microvalves. The PZT pusher works at high frequencies to produce large flow rates (proportional to displacement traveled) and high pressures. As a component of the hydraulic actuator, the microvalves are challenged in matching the requirements of the PZT in terms of high operational frequencies, large flow rates and high-pressure support capabilities. In order to fulfill these requirements, the authors have developed robust self-assembled solid nickel micro valve arrays consisting of 80 single micro check valves, to achieve the required flow rate (>10 cc/second). A single micro check valve consists of an inlet channel (200 μm in diameter), a specially designed valve flap held by four identical micro beams, and outlet channels. All these structures are made from electroformed nickel and are self-assembled during a novel in situ UV-LIGA fabrication process. Finite element simulation results show that the micro check valve has a 1st resonant frequency of 16 kHz and is able to support pressures greater than 10 MPa. Test results show the flow rate is 19 cc/s at a pressure difference of 100 psi, and is roughly proportional to the pressure applied. Based on Poiseuille's law, it is reasonable to predict larger flow rates if higher-pressure differences are applied.

In this paper, we propose a resonator structure with a high Q factor, which has the potential to replace the Quartz crystal. In order to achieve a higher Q, complete decoupling of the resonating structure from the supporting ends is desired. One of the ways of achieving this is to distribute the stress uniformly throughout the support beam rather than their being concentrated at the fixed ends. This suggests a resonating mass supported by torsion wires. Here, three resonating structures are connected in a serial fashion. The outer two resonators act as interfaces to the external oscillator circuit, while the centre one is fully decoupled. The losses at the end of torsion wires are thus kept to lowest value. The other losses, namely damping and internal friction losses, are kept to a minimum by providing vacuum and using high quality material for the torsion wire. Modal analysis and static stress analysis were done on the structures and results clearly show the fundamental torsion mode of vibration and extremely small stresses at the fixed ends of the torsion wire.

This paper reports on compensation for human eye aberration using a membrane deformable mirror(DM) which is fabricated by the MEMS process. The DM consists of a silicon(Si) membrane formed by processing of an SOI wafer and 85 electrodes. The diameter of Si membrane is 12mm and the maximum displacement is 16μm at a driving voltage of 180V. We have successfully demonstrated compensation for a model eye's aberration by using the DM. The model eye's aberration measured by the Shack-Hartmann wavefront sensor was expanded into Zernike polynomials and the driving voltages for the DM were decided so that the membrane shape would cancel out the eye's aberration by using appropriate voltage arrangements for each of the Zernike polynomials, these arrangements being predetermined experimentally. We have corrected the aberration of the model eye to less than 0.1μm-RMS. In this experiment, the effective diameter of the DM was 7.5mm, and the pupil of the model eye was 8.5mm.

In some implanted and distributed system, the power consume of these devices is tiny (generally just at uW level), and effective, long term, power supplier are lacking. For this need, several forms of vibration-driven MEMS micro generator are possible and are reported in the literature, with potential application areas including distributed sensing and ubiquitous. Our goal is to develop a micro power source translating the ambient vibration energy into the electric power which can offer 30uW power to some sensors. In our work, we designed the power generator based on a charge induced by a electret transported between two parallel capacitors. It consists of combed in-plane capacitor, electret and selenium rectifier. The combed in-plane capacitor is the key part of the generator; it will fulfill the charge transportation and translation of the energy. We design the structure of the capacitor and simulate the amplitude-frequency characteristic and phase-frequency characteristic. And then the electric-mechanic coupling is simulated, and we know the relationship between output voltage, power density and frequency. Finally a micro power generator is designed and its dimension is 8000*3000um.When the exterior oscillation is 10um and the load is 1e-6ohm, the output power is 30uW and the voltage is 4.1V.

Basic layout of micro-relays based on electrostatic operation principle with adjustable parameters (ESRA) for flat-parallel electrodes placement is characterised by that the anchor with immovable electrode is connected with base substrate by elastic holders and is fixed on a reversing electro-mechanical micro-drive. The ledges are formed in the elastic holders in an appointed place and at a designed height, on which the contacts of controlling circuit are placed. Due to elastic bond of the anchor, the micro-drive enable to change gradually inter-electrodes distance t providing stepless Uon adjustment in the 0.03 to 2.80 range of nominal operation voltage. Simultaneously, the t_c increases or decreases proportionally maintaining the appointed value of ΔU gradient of U_on and U_off voltages. In practice, the minimum ΔU value could be close to zero. Hence, the ESRA of the same typical size could operate in electric circuits under various fixed U_on values. Its usage is particularly effective in layouts providing non-stationary processes control (for instance, variation of temperature or effort in accordance with appointed program) owing to corresponding set of necessary inter-electrodes distance using the micro-drive.