We present a lamellar grating interferometer realized with MEMS technology. It is used as time-scanning Fourier transform spectrometer. The motion is carried out by an electrostatic comb drive actuator fabricated by silicon micromachining, particularly by silicon-on-insulator technology. We have measured the spectrum of an extended white light source with a resolution of 1.2 nm at a wavelength of 436 nm, and of 13 nm at 1544 nm. The wavelength accuracy is better than 0.5 nm and the inspected wavelength range extends from 380 nm to 1700 nm. The optical path difference maximum is 226 μm and is limited by the mechanical instability of the actuator. The dimension of the device is 7 mm x 8 mm x 0.5 mm. The device includes two individual lamellar grating spectrometers operated by the same actuator, allowing the immediate calibration of the optical path difference.

In the last few years the importance of Micro Opto Electro Mechanical Systems (MOEMS) increased significantly in technical applications. This is caused by the possibility of combining micro optical elements with micromachining technology that makes it feasible to develop new systems with high volumes and low prices. In this article, we report on the realization of a NIR (near infrared) spectrometer in the range of 900 - 2000 nm using MOEMS technology. It is based on a scanning mirror chip, which mirror plate is structured with a diffractive aluminium layer on top. This offers the possibility to fabricate a spectrometer, which needs only one single InGaAs detector photo diode. In contrast to common CCD arrays, the obtained resolution is only limited by the performance of the spectrometer (entrance slit, exit slit, focus length, diffractive element). The scanning grating chip operates at a frequency of 500 Hz, at an optical scan range of ± 4°. The whole spectrometer has a size of 90 x 60 x 50 mm. For first investigations of the performance, IR LEDs (light emitting diode) with 1300, 1450 and 1550 nm wavelength have been measured.

The triangulation distance sensor is constructed using the originally proposed wafer bending technique. Since the bending process is final in the fabrication sequence, the planer photolighography can be combined. On the Si wafer, the elements are pre-aligned at the unfolded planer condition. The position sensitive detector (PSD), mirror, and alignment pit for the collimation ball lens are prepared. The realized sensor substrate is 1.4mm in depth. Taking the advantage of the batch fabrication, 2x2 sensor array is prepared. The dynamic range of 4mm with ± 1% noise is confirmed.

Design and analysis of a novel pressure sensor based on a silicon-on-insulator asymmetric integrated vertical coupler is presented. The coupler is composed of a single mode low index waveguide and a thin silicon slab. Wavelength selective optical modulation of asymmetric vertical coupler is examined in detail. Its potential for sensing applications is highlighted as an integrated optical pressure sensor which can be realized by standard silicon micro-fabrication. Sensitivity of transmission of such couplers on refractive index change of silicon slab ensures that they are good candidates for applications requiring high sensitivities.

The proposed pixel matrix display consists of two plastic elements: a planar waveguide which plays the role of a light reservoir and a deformable thin membrane with a matrix of pillars. On the bottom side of the membrane that touches the light reservoir there is an electrode surrounding all pillars and leaving tops of pillars transparent. The light reservoir has a matrix of individual electrical contacts so that the display can be addressed pixel by pixel and switched on by applying a voltage to the electrical contacts on the light reservoir and the membrane electrode. The electrostatic force locally deforms the membrane and puts the pillars in contact with the light reservoir, therefore, coupling light into the membrane. A demonstrator of a polymer-based pixel matrix display is fabricated in MOEMS technology. The proof-of-principle experiment is made on a 20x20 pixel matrix with an active display matrix area of 5x5 mm², a light emitting diode illumination and 80 V applied to address pixels.

The rapid commercialization and long-term reliability of optical MEMS is greatly facilitated by a Design-for-Reliability mindset, relying on an interdependent development framework simultaneously optimizing design, materials choices, processing, reliability, subsystem design, and packaging. Even with the best mechanical design, the electrical design and packaging choices of these devices has a large impact both on performance (e.g., speed and stability) and on reliability (e.g., corrosion and dielectric or gas breakdown). In this paper we discuss the reliability and performance of two-axis MEMS micromirrors and present several design, processing and packaging steps that were needed to achieve open-loop drift-free operation and mean-time-to-failure in excess of 2000 years. In particular the relationship between leakage currents and the accumulation of quasi-static charge in dielectrics are discussed, along with several techniques to mitigate charging and the associated drift in electrostatically actuated or sensed MEMS devices. Two key parameters are shown to be the electrode geometry and the conductivity of the dielectric. Electrical breakdown in sub-micron gaps is presented as a function of packaging gas and electrode spacing. We discuss the trade-offs involved in choosing gap geometries, dielectric properties, and packaging solutions. Finally galvanic corrosion of poly-silicon in HF release etch baths is discussed along with techniques to minimize this corrosion.

New MEMS device are perpetually being proposed and concepts are approved by means of demonstrator devices. Volume production of MEMS however requires more. The fabrication process must be suitable for large numbers of wafers at acceptable cost and yield. Devices must be tested and packaged. Both are major cost factors. Reliability must be qualified. Finally the product must compete with other (established?) solutions in cost, performance and reliability. We report on the fabrication end-test of the micro scanning mirror, a MEMS device for the resonant large-angle deflection of a laser beam at low operation voltage. The end-test involves: 1. wafer-level end-test of critical parameters on 100% of the chips, 2. full characterization of a random sample, and 3. reliability tests on representative samples. Emphasis is put on the wafer-level end-test of the mechanical properties.

Modeling, manipulating and testing of the dynamic performances of micro-electro-mechanical systems (MEMS) devices are very important in building successful microsystems. However, MEMS devices pose several significant difficulties in characterization. The physical dimensions of MEMS devices are such that conventional measurement and characterization techniques cannot be used since the sensor would interfere with the measurement. Hence, non-contact sensing systems offer many advantages for MEMS characterization. One important issue in characterizing and troubleshooting MEMS devices is the differentiation between electrical and mechanical effects. By definition, MEMS devices are comprised of electrical and mechanical components forming integrated electro-mechanical systems. The dynamic response of these devices is often difficult to determine because of the coupled electro-mechanical behavior. It is also known that the dynamic response is influenced by the limitation of fabrication processes and the material conditions. Hence, this paper proposes a simpler method to verify the dynamic behavior of MEMS structures using Laser Doppler Velocimeter (LDV). Non-contact vibration measurements are thus possible with such a testing system that can lead to significant improvements in the accuracy and precision of MEMS testing. The dynamic experiments are conducted on different devices and the test results are compared with prediction.

Polymer based microfluidic devices have an important potential use in BioMEMs applications due to the low cost and biocompatibility. However, sealing the devices hermetically without blocking the channels, altering their dimensions or changing the surface properties is a challenging issue in their fabrication. In this paper a microwave-based sealing technique using a polymethylmethacrylate (PMMA) substrate and conductive polymer (polyaniline) is presented. The developed novel bonding technique has achieved precise, well-controlled and selective heating, which causes localized melting of the polymer substrates. At the joint interface, patterned polyaniline features absorb electromagnetic radiation and convert it into heat, which facilitates the microwave bonding of two PMMA substrates. This new approach can easily seal microfluidic devices with micron-sized channels without blocking or destroying the integrity of the channel. Microfluidic channels of 400 μm and 200 μm wide were sealed using a microwave power of 300 Watts, in less than 20 seconds. The microfluidic channel fabrication techniques, polyaniline patterning method at the interface and bonding evaluation such as sample cross section and leak test are discussed. The dielectric properties of polyaniline and PMMA at 2.45 GHz frequency are also evaluated by using the open probe technique, which shows PMMA is essentially transparent to microwave energy.

This paper deals with the latest development of micromachining technology to fabricated nanoscopic structures and applications to nano- and bio- technologies. We have realized well-defined nano structures by using the combination of conventional photo-lithography, LOCOS, and wet anisotropic etching of silicon. The technology has been applied to develop micromachined field emitters that operated in the TEM (transmission electoron microscope) chamber, and the degradation process of the silicon tips was in-situ observed. In addition to this nanoelectromechanical research topics, we have recently expanded our research field into bio- and molecular engineering: silicon nanofabricated twin probes were used to directly manipulate DNA molecules, for instance. Futhermore, bio-molecular linear motors were tested as a mechanical power source for mechanically transferring micro/nano particles.

The optical application of electrowetting-on-dielectric (EWOD) using thin dielectric layers is the focus of this paper. An optical switching configuration is designed with transparent indium-tin-oxide (ITO) electrodes and glass substrates as well as a transparent dielectric film between the liquid and the electrodes. A polyimide layer with a thickness of 0.5 μm to 1.5 μm and a top coating of 0.5 μm PTFE as hydrophobic surface has been used as dielectric film. Experimentally we present a significant change in the contact angle up to 56° applying a voltage of 155 V. The wettability of the surface can be controlled and a liquid flow is achieved by applying a voltage below 100 V. The saturation of contact angle is described by a model including a contact angle dependent resistance of the dielectric layer as fitting parameter and a constant resistance of the water droplet. The resistances have been confirmed by independent measurements. Based on these results optical switching has been performed by the principle of total reflection. Thereby the refractive index of the optical beam path is changed between the total reflection condition at an interface and transmission. This operation is realised by moving a water droplet between two glass plates. Within this concept addressable operations of a liquid on a fluidic chip and the integration of optical guiding and switching of light is possible. The application of EWOD for optics can be fundamental for the integration of micro-optics and fluidics in one device and the development of new micro-opto-electro-mechanical systems (MOEMS).

Early enzymatic identification and confirmation is essential for diagnosis and prevention as in the case of Acute Myocardial Infarction (AMI). Biochemical markers continue to be an important clinical tool for the enzymatic detection. The advent of MEMS devices can enable the use of various microstructures for the detection of enzymes. In this study, the concept of MEMS is applied for the detection of enzyme reaction, in which microcantilevers undergo changes in mechanical behavior that can be optically detected when enzyme molecules adsorb on their surface. This paper presents the static behavior of microcantilevers under Horse Radish Peroxide (HRP) enzyme reaction. The reported experimental results provide valuable information that will be useful in the development of MEMS sensors for enzymatic detection. The surface stress produced due to enzyme reactions results in the bending of cantilevers as similar to the influencing of thermal stress in the cantilevers. This paper also reports the influence of thermal gradient on the microcantilevers.

A controlled drug delivery system in which drug release is achieved by actuating an array of polymeric valves on a set of drug reservoirs is introduced. The valves are bilayer structures with one layer, a thin film of evaporated gold and the other, electrochemically deposited polypyrrole, which is also called “artificial muscle”. The valves are made in the shape of flaps fixed on one side to the valve seats. Drug reservoirs are covered by an array of such valves. Release of the drugs stored in the reservoirs is accomplished by bending the bilayer flaps back with a small applied bias. The fabrication procedures and proof-of-principle drug release experiments for this controlled drug delivery device are described. Energy consumption of this reversible valve design is compared with metal corrosion based valves developed earlier by other groups and our group.

Designing manufacturable MEMS devices requires a strong link between design and process engineers. Establishing systematic design principles through a common CAD framework facilitates this. A methodology for MEMS Design for Manufacturing (DFM) is presented that focuses on solid process and design qualification through systematic parametric modeling and testing, from initial development of specifications to volume manufacturing. This strategy has been applied to two MEMS fabrication processes, including CMOS-compatible SOI micromachining and metal-nitride surface micromachining. Case studies of designed, simulated, fabricated and characterized test structures demonstrate the methodology and benefits of the outlined DFM approach - including extraction of material properties and process capabilities enabling a prediction of fabricated device performance distribution. The overall result is a MEMS product design framework that incorporates a top-down design methodology with parametric re-usable libraries of MEMS, IC and relevant system components capable of allowing to design within a specific process (via a process design kit) to enable virtual manufacturing.

Dynamic behavior of a comb-driven torsional microscanner is governed by a nonlinear parametric differential equation. Theoretically, such systems have multiple resonances located near the integer fractions of twice the mechanical resonance frequency. The number of observable parametric resonances strongly depends on the damping of the system, whereas the stable and unstable operating regions are determined by drive-voltage and drive-frequency. In atmospheric pressure, only first few of these parametric resonances are observable within the operation voltage range of the devices. This paper explores the effect of damping on the various characteristics of parametric resonances and some unusual scanner behavior rarely seen in mechanical structures. A numerical and an analytical model for comb-driven microscanners are presented. Frequency responses of various devices are experimentally measured inside a vacuum chamber at different ambient pressures ranging from atmospheric pressure to 30 mTorr. Experimental results are compared with analytical and simulation results.

Many studies on optical switches have been performed in an attempt to develop optical information networks to speed information technology. In reality, however, mirror manipulators cannot be applied to multiple input and output systems due to both insufficient output displacements by the mirror parts inside the manipulator, and the difficulty of designing structures and mechanisms suitable for multi-dimensional manipulation. The principal reasons for insufficient displacement are the high rigidity of the elastic parts compared to the available driving forces and the pull-in effect. Therefore, in order to develop optical switches capable of multiple input and output switching, we suggest a novel 2-DOF(degree of freedom) electrostatic microactuator. The actuator is composed of one mirror with four beams laid about it in a corkscrew pattern, with four corkscrew electrodes on the substrate below and one mirror support pyramid situated under the mirror. Using electrostatic force, one or more of the beams are attracted from their outer ends toward the substrate. The mirror is then tilted by an angle proportional to the attracted length along the beam. The inclination and direction of the mirror are determined by the combined attracted length of the four beams. In this work we derive the mathematical model for the corkscrew beam microactuator for optical switches and show that this mathematical model accurately simulates the device by comparison with finite element analysis results. We use this mathematical model for design of the microactuator. Further we show that the designed optical switch microactuator is capable of rotating the mirror from +32 to -32 degrees about two axes with a maximum operating voltage of 163 volts. Finally, stress analysis of the actuator shows that the generated stress in the structure is at most 369 MPa.

In this paper we present the analytical and experimental investigation of the air damping of micromachined scanning mirrors with out-of-plane comb drive actuation. A simple, compact model for the damping torque is derived by estimating the orders of magnitude of certain damping contributors. Viscous damping in comb finger gaps is estimated to be the dominant contributor. Because the comb fingers disengage as the scan amplitude increases, the damping coefficient is dependent on the amplitude of angular vibrations. Experimental measurements are presented for a variety of comb-finger geometries. The comb finger length, width, and the gap between comb fingers are varied, and the damping behaviour for single-axis scanning is characterised by measuring the decay rate of free oscillations. The damping is characterised by the exponential decay constant δ, found by fitting to the decaying oscillation amplitude. The predictions of the analytical model are compared to these experimental damping measurements.

In this paper, a tilting micromirror device that can achieve designed angle is proposed. A lever structure, driven by electrostatic actuators, was used to enlarge tilting angle. To obtain precise deflecting angle, the lever structure is constrained by the substrate. By applying a voltage, the electrostatic actuators drive the lever down to the substrate such that the micromirror device on the opposite side of the lever structure could be lifted. PolyMUMPs process was used to fabricate proposed micromirror devices. The actuators are simulated to investigate characteristics of the micromirror devices. Experimental results had indicated that the micromirror device could reach 10-degree tilting angle with 80V driving signal with 6.4% relative error compared to designed model.

This paper reports on the design, modeling, fabrication and measurement of a novel-structured film bulk acoustic resonator (FBAR) that allows frequency tuning by MEMS actuation. FBAR's are micromachined frequency controlling devices working in RF regime. For many applications, a small range of tuning is desired to cope with drifts from different origins. To realize this functionality, it has been suggested to place tunable elements such as variable capacitors or inductors in the circuit. A conventional approach, in which an external element is used, would introduce parasitics and might seriously degrade the quality factor of the system. In contrast, our work integrates the piezoelectric resonating film and the tuning element to build a compact structure. By reducing possible parasitics and electrical resistance, this structure enables frequency tuning while maintaining a high quality factor.

RF-MEMS switches are commonly electrostatically actuated. This way of actuation has the advantage of technological simplicity. However the actuation voltage is relatively high. Piezoelectric actuation can have significantly lower actuation voltages, depending on the used materials and geometries. Analysis shows that clamped-free beams and clamped-clamped beams can have a reasonable deflection when aluminum nitride is used as the piezoelectric material. A five mask monolithic process has been developed for the realization of piezoelectrically actuated cantilevers and RF-MEMS switches. The complexity of this process is comparable with the complexity of the process for electrostatically actuated switches. Deflections of piezoelectrically actuated cantilever beams have been measured. Due to a high stress gradient in the beams, the assumptions that have been made in the analysis are not valid anymore. Finit element simulations were needed to verify the measurement data. The simulations fit with the measurements when the following values are taken for the properties of the aluminum nitrde film: Young's modulus E_p = 320 GPa and piezoelectric coefficient d₃₁ = -3.2 pC/N.

This paper reports on the investigation of the potentialities of the MEMS technologies to develop innovative microsystem for millimetre wave communication essentially for space applications. One main issue deals with the robustness and the reliability of the equipment as it may difficult to replace or to repair them when a satellite has been launched. One solution deals with the development of redundancy rings that are making the front end more robust. Usually, the architecture of such system involves waveguide or diode technologies, which present severe limitations in term of weight, volume and insertion loss. The concept considered in this paper is to replace some key elements of such system by MEMS based devices (Micromachined transmission lines, switches) in order to optimize both the weight and the microwave performance of the module. A specific technological process has been developed consisting in the fabrication of the devices on a dielectric membrane on air suspended in order to improve the insertion loss and the isolation. To prove the concept, building blocks have been already fabricated and measured (i.e micromachined transmission and filter featuring very low insertion loss, single pole double through circuits to address the appropriate path of the redundancy ring). We have to outline that MEMS technology have allowed a simplification of the architecture and a different system partitioning which gives more degree of freedom for the system designer. Furthermore, it has been conducted an exhaustive reliability study in order to identify the failure mechanisms. Again, from the results obtained, we have proposed an original topology for the SPDT circuit that takes into account the reliability behaviour of the MEMS devices and that allow to prevent most of the failure mechanisms reported so far (mainly related to the dielectric charging effect). Finally, the active device (millimetre wave low noise amplifier) will be reported on the MEMS based chip using flip chip technology to integrate the Microsystem.

Mobile technologies have relied on RF switches for a long time. Though the basic function of the switch has remained the same, the way they have been made has changed in the recent past. In the past few years work has been done to use MEMS technologies in designing and fabricating an RF switch that would in many ways replace the electronic and mechanical switches that have been used for so long. The work that is described here is an attempt to design and fabricate an RF MEMS switch that can handle higher RF power and have CMOS compatible operating voltages.

This article describes and provides valuable information for companies and universities with strategies to start fabricating MEMS for RF/Microwave and millimeter wave applications. The present work shows the infrastructure developed for RF/Microwave and millimeter wave MEMS platforms, which helps the identification, evaluation and selection of design tools and fabrication foundries taking into account packaging and testing. The selected and implemented simple infrastructure models, based on surface and bulk micromachining, yield inexpensive and innovative approaches for distributed choices of MEMS operating tools. With different educational or industrial institution needs, these models may be modified for specific resource changes using a careful analyzed iteration process. The inputs of the project are evaluation selection criteria and information sources such as financial, technical, availability, accessibility, simplicity, versatility and practical considerations. The outputs of the project are the selection of different MEMS design tools or software (solid modeling, electrostatic/electromagnetic and others, compatible with existing standard RF/Microwave design tools) and different MEMS manufacturing foundries. Typical RF/Microwave and millimeter wave MEMS solutions are introduced on the platform during the evaluation and development phases of the project for the validation of realistic results and operational decision making choices. The encountered challenges during the investigation and the development steps are identified and the dynamic behavior of the infrastructure is emphasized. The inputs (resources) and the outputs (demonstrated solutions) are presented in tables and flow chart mode diagrams.

We report on a 4x4 optical matrix switch for telecom application. It consists of a 4x4 array of vertical mirrors that have the same pitch as the fibers of commercially available fiber ribbons (250 μm). This compact design enables a parallel assembly to optical components, which simplifies the time consuming and costly process for switches with larger pitch. Additionally, a small pitch leads to a short optical coupling length, which facilitates the integration of a suitable collimation system. However there are physical limitations for optical MEMS in conjunction with assembled micro-optics. The optical beam exiting a collimator diverges, the divergence angle is indirectly proportional to the beam waist and the coupling length increases quadratically. Our calculations show that for a pitch of 250 µm a mirror height of 100 μm is optimal. The mirrors are monolithically etched onto a platform etched during a previous step. No assembly of the mirrors to the actuators is needed. Alignment structures for the optical components are etched during the same step as the mirrors, which lead to self aligned structures. The platform is supported by 150 μm long torsion beams with sub-micron diameter. The electrostatic actuation voltage is given by a separate chip. The mirror moves out of the optical path when the platform is actuated and goes to the switching state if no voltage is applied. The first prototypes have been actuated at 200 V, which agrees with a CoventorWare simulation used for designing the device. Light was successfully switched with a 4x4 OXC. An 8x8 OXC is shown and electrostatically characterized.

The second generation circular digital variable optical attenuator (CDVOA) with an effective area of 1500 μm diameter has been designed and fabricated based on SOI technology. C-band incoming Gaussian light can be reflected to an outgoing fiber from a shiny circular area, which is divided into sectors that can be individually tilted and addressed electrostatically to achieve variable light attenuation. Using a delay mask process, each movable component i) has an underlying ridge frame to maintain flatness, ii) is suspended by two micro beams at a bridge structure that connects to a handle where aluminum electrode is located underneath, and iii) is separated by wall structures at the handle area to reduce crosstalk from adjacent electrodes. Critical fabrication processes including the mirror and chip release are performed using a HF vapor phase etcher. Fluidic pressure and chip-dicing shocks are avoided. Initial results show that a mirror sector suspended by two 345 μm long beams with a cross-section of about 5×5 μm² can be tilted to 2.8° at about 18 V driving voltage. Initial interferometric measurement gives estimated individual mirror flatness after metallic reflective coating to be about λ/15. The assembled chips are ready for further testing and characterization.

A detailed study of the tuning characteristic of a novel MEMS-based tunable optical filter is presented together with supporting characterization results. The device is based on a Fabry-Perot interferometer employing a solid-state silicon resonator and silicon-based distributed Bragg reflectors (DBR). It is fabricated as a free-standing membrane, which is suspended through micro-machined arms. Tuning is achieved by thermal modulation of the resonator’s optical thickness. The tuning behavior of thin film interference filters differs significantly from filters based on an etalon structure. An analytical approach is presented to include effects caused by the Bragg reflectors. Based on this model different material systems are investigated in order to improve the achievable tuning range. A maximum reflectance of 99.8 % and a stop band width of 783 nm are achieved. A minimum spectral width of 1.19 nm and an insertion loss of 1.7 dB have been measured in transmission measurements for filter membranes, consisting out of a λ/2 layer of amorphous silicon and Bragg reflectors each with 12 λ/4 layer-pairs of silicon nitride and silicon dioxide. Using external heating the filter shows a tuning efficiency of 51.7 pm K^-1, as predicted through the proposed effective resonator length model.

We report on an angle-tunable oblique incidence resonant grating filter that can be used to drop individual channels from the C-band for incident TE-polarized light. For tuning purpose, the filter is glued onto a tiltable platform of a MEMS device. Continues scanning of the platform allows to monitor channel presence and power. The reflected wavelength is tuned by changing the angle of incidence of the resonant grating filter, which is composed of two thin films with a grating pattern on top of it. The first layer on a glass substrate acts as a waveguide, and the second layer separates the waveguide from the grating. The grating has been patterned by holographic recording and dry etching. The filter works over a wavelength range of 1520-1580 nm and its response has a Lorentian shape with 0.5 nm FWHM peak width. The MEMS part is based on SOI technology and is processed in only two DRIE steps. The platform measures 2 x 2 mm² with a through-hole of 1.6 x 1.8 mm² for light transmission. Two arrays of combs attached to the platform as well as a set of four static combs are used to electrostatically incline the platform by ± 4° with a driving voltage of about 60 V.

In this paper we present the design and the experiments performed to obtain a micromechanical voltage tunable Fabry-Perot interferometer integrated with a p-n photodiode on a silicon substrate. It can be used as a voltage tunable filter for the input radiation or as a voltage controlled attenuator to regulate the light from a monochromatic source. Different solution have been analyzed and experimented. The top mirror of the Fabry-Perot cavity is a doped poly-Si or Au/SiO₂ movable membrane, electrostatically actuated, obtained using Si micromachining. A complex design process was performed: optical, electomechanical and technological. All these phases were performed interactively. Different materials were considered in order to perform an optimum design. Experimental micromachined interferometers were obtained using two techniques: (1) surface micromachining, and (2) anisotropic etching of (111)-oriented Si wafers, combined with an isotropic pre-etching step. These processes were optimized and matched to the photodiode fabrication process. Monolithic integrated interferometers coupled to p-n photodiodes were obtained.

We have developed a novel low-cost electrostatically actuated 1x2 fiber switch which basically consists of two active components only, i.e. metalized movable fibers and fixed electrodes. With this set-up, a direct movement and, additionally, a self-alignment of the fibers is performed. In contrary to other MEMS designs no complex moving parts are necessary. It is possible to fabricate the switch with low-cost polymer techniques. Driving voltages below 60V and switching times below 8ms have been demonstrated with these polymer devices. The optical fiber switch presented utilises electrostatic forces to move one incoming fiber with respect to the two outgoing fibers. Simultaneous application of the actuation voltage to the inlet fiber and the respective outlet fiber will pull both fibers into the same corner of the actuation chamber, where they settle in a perfect optical alignment.

This work presents the micro-machined 2-D switch array for use on free-space optical interconnect platform integrated with a digital 1x8 de-multiplexer control circuit together. Moreover, this device employs electrostatic actuation for light beam directions control. The CMOS-MEMS array-based optical platform contains 10x10 circular micromirrors switching spots, the diameter of each mirror is about 50 μm and the overall chip size is around 2 mm by 2 mm. The commercialized simulation softwares were used to validate the micromirror design and elucidate the behavior of the micromirror before fabrication. The post-process simply employs HF based solution to etch silicon dioxide layer to release the suspended mirror structures. The micromirror array is actuated using an electrostatic force. The results reveal that the micromirror has a tilting angle of around 8° according to the triangular relation with a driving voltage of 18V at pull down state. Also described herein are the general principles of the light-beam switching method used, the detailed of device design, the post-CMOS fabrication process flow, the result of simulations and preliminary experimental results are discussed.

We present Deep Lithography with Protons (DLP) for the fabrication of ultra-dense fiber coupling elements which consist of circular, conical-shaped alignment features, ordered in a 2D array with high-precision pitches. This technology relies on the irradiation of PMMA-resist layers with a swift proton beam featuring a well-defined circular shape, followed by a selective development of these exposed zones. To increase the coupling efficiency, the DLP-technology allows to integrate uniform spherical micro-lenses, which are created by a controlled swelling of the proton-bombarded domains in a monomer vapor, in front of the micro-alignment holes. We will first discuss our work on the improvement of the DLP irradiation and development process step to enhance the coupling efficiency and the field-installability of the connector components. Furthermore, we will illustrate the optical design of micro-lens arrays and their integration in fiber connectors with improved tolerances.

Batteries based on three dimensional microstructures are expected to offer significant advantages in comparison to conventional two dimensional batteries. One of the key elements for creating new types of 3D microbatteries is fabricating high-aspect-ratio carbon structures. Our efforts on building positive photoresist structures include: (1) casting photoresist in 3D molds made by DRIE before pyrolysis; (2) multi-exposure and multi-developing processes, and (3) using embedded masks in multi-layer photoresists. Another effort is the fabrication of high-aspect-ratio carbon structures using negative photoresist. We manufactured high-aspect-ratio (~10:1) carbon posts by pyrolysis from negative photoresists in a simple one-step process. Simulation results showed that current density is strongly influenced by the biasing pattern and the geometry of the electrodes themselves. Current density (and therefore power density) is stronger at the edge of electrodes-implying that closer spacing of the electrodes will provide a denser current concentration. Electrochemical tests demonstrate that these C-MEMS electrodes can be charged/discharged with Li. A C-MEMS battery approach has the potential to solve both manufacturing and materials problems simultaneously.

Forecasters and analysts predict the market size for microsystems and microtechnologies to be in the order of $68 billion by the year 2005 (NEXUS Market Study 2002). In essence, the market potential is likely to double in size from its $38 billion status in 2002. According to InStat/MDR the market for MOEMS (Micro Optical Electro Mechanical Systems) in optical communication will be over $1.8 billion in 2006 and WTC states that the market for non telecom MOEMS will be even larger. Underpinning this staggering growth will be an infrastructure of design houses, foundries, package/assembly providers and equipment suppliers to cater for the demand in design, prototyping, and (mass-) production. This infrastructure is needed to provide an efficient route to commercialisation. Foundries, which provide the infrastructure to prototype, fabricate and mass-produce the designs emanating from the design houses and other companies. The reason for the customers to rely on foundries can be diverse: ranging from pure economical reasons (investments, cost-price) to technical (availability of required technology). The desire to have a second source of supply can also be a reason for outsourcing. Foundries aim to achieve economies of scale by combining several customer orders into volume production. Volumes are necessary, not only to achieve the required competitive cost prices, but also to attain the necessary technical competence level. Some products that serve very large markets can reach such high production volumes that they are able to sustain dedicated factories. In such cases, captive supply is possible, although outsourcing is still an option, as can be seen in the magnetic head markets, where captive and non-captive suppliers operate alongside each other. The most striking examples are: inkjet heads (>435 million heads per year) and magnetic heads (>1.5 billion heads per year). Also pressure sensor and accelerometer producers can afford their own facilities to produce the numbers they want (several millions per year). The crossover point where building a dedicated facility becomes a realistic option, can differ very much depending on technology complexity, numbers and market value. Also history plays a role, companies with past experience in the production of a product and the necessary facilities and equipment will tend to achieve captive production. Companies not having a microtechnology history will tend to outsource, offering business opportunities for foundries. The number of foundries shows a steady growth over the years. The total availability of foundries, however, and their flexibility will, undoubtedly, rely on market potential and its size. Unlike design houses, foundries need to realise a substantial return on the "large" investments they make in terms of capital and infrastructure. These returns will be maximised through mass-produced products aimed at "killer" applications (accelerometers are only one example). The existence of professional suppliers of MOEMS packaging and assembly is an essential element in the supply chain and critical for the manufacturing and commercialisation of MOEMS products. In addition, the incorporation of packaging and assembly techniques at the front-end of the engineering cycle will pay back in terms of financial savings and shorter timescales to market. Packaging and assembly for MOEMS are, in general, more costly than their equivalents for standard integrated circuits. This is, primarily, due to the diversity of the interconnections (which are multi-functional and may incorporate: electrical, optical, fluidic etc). In addition, the high levels of accuracy and the potential sensitivity of the devices to mechanical and external influences play a major role in the cost aspects of the final MNT product. This article will give an overview of the package/assembly providers and foundry business models and analyse their contribution to the MOEMS supply chain illustrated with some typical examples. As we believe that commercial services are the main basis for the breakthrough of MOEMS technology, we only cover commercial package/assembly and foundry services and not the ones offered by universities and research labs.

This study presents a novel method based on the surface acoustic wave (SAW) sensor, for monitoring the thickness of a silicon membrane in real time during wet etching. Similar to accelerometers and pressure sensors, some micro-electro-mechanical systems (MEMS) devices require the thickness of silicon membranes to be known precisely. Precisely controlling the thickness of a silicon membrane during wet etching is important, because the thickness strongly affects post-processing and device performance. Moreover, the proposed surface acoustic wave sensor allows the thickness of a silicon membrane to be monitored from a few μm to hundreds of μm in situ, which depends on the periodicity of interdigital transducers (IDT). A novel method, which differs from any in previous work on etch-stop techniques, is developed in-situ for monitoring the thickness of a silicon membrane during wet etching. In summary, the proposed method for measuring the thickness of a silicon membrane in real time, is highly accurate; is simple to implement, and can be mass-produced. This work also describes the principles of the method used, detailed process flows, the method of taking measurements and the simulated and experimental results. The theoretical and measured values differ by an error of less than 2.50μm, so the results closely agree with each other.

Reagentless mechanical cell lysis was demonstrated on a microfluidic CD (Compact Disc) microfabricated in PDMS (Polydimethylsiloxane). The motion of beads in a lysis chamber on the CD causes disruption of mammalian (CHO-K1), bacterial (Escherichia coli), and yeast (Saccharomyces cerevisiae) cells. Interactions between beads and cells are generated in the rimming flow established inside a partially filled annular chamber in the CD rotating around a horizontal axis. To maximize bead-cell interactions, the CD was spun forward and backwards around this axis, using high acceleration for up to 7 minutes. Based on our theoretical work, we investigated the following control parameters: bead density, angular velocity, acceleration rate, and solid volume fraction, all of which influence cell lysis efficiency. Cell disruption efficiency was verified either through direct microscopic viewing or measurement of DNA concentration after cell lysing. Lysis efficiency relative to a conventional lysis protocol was also determined. In the long term, this work is geared towards CD based sample-to-answer nucleic acid analysis which will include cell lysis, DNA purification, DNA amplification, and DNA hybridization detection.

A DNA hybridization and detection unit was developed for a compact disc (CD) platform. The compact disc was used as the fluidic platform for sample and reagent manipulation using centrifugal force. Chambers for reagent storage and conduits for fluidic functions were replicated from polydimethylsiloxane (PDMS) using an SU-8 master mold fabricated with a 2-level lithography process we developed specially for the microfluidic structures used in this work. For capture probes, we used self-assembled DNA oligonucleotide monolayers (SAMs) on gold pads patterned on glass slides. The PDMS flow cells were aligned with and sealed against glass slides to form the DNA hybridization detection units. Both an enzymatic-labeled fluorescence technique and a bioluminescent approach were used for hybridization detection. An analytical model was introduced to quantitatively predict the accumulation of hybridized targets. The flow-through hybridization units were tested using DNA samples (25-mers) of different concentrations down to 1 pM and passive assays (no flow), using samples of the same concentrations, were performed as controls. At low concentrations, with the same hybridization time, a significantly higher relative fluorescence intensity was observed in both enzymatic and bioluminescent flow-through assays compared to the corresponding passive hybridization assays. Besides the fast hybridization rate, the CD-based method has the potential for enabling highly automated, multiple and self-contained assays for DNA detection.

One significant challenge facing biosensor development is packaging. For surface acoustic wave based biosensors, packaging influences the general sensing performance. The acoustic wave is generated and received thanks to interdigital transducers and the separation between the transducers defines the sensing area. Liquids used in biosensing experiments lead to an attenuation of the acoustic signal while in contact with the transducers. We have developed a liquid cell based on photodefinable epoxy SU-8 that prevents the presence of liquid on the transducers, has a small disturbance effect on the propagation of the acoustic wave, does not interfere with the biochemical sensing event, and leads to an integrated sensor system with reproducible properties. The liquid cell is achieved in two steps. In a first step, the SU-8 is precisely patterned around the transducers to define 120 μm thick walls. In a second step and after the dicing of the sensors, a glass capping is placed manually and glued on top of the SU-8 walls. This design approach is an improvement compared to the more classical solution consisting of a pre-molded cell that must be pressed against the device in order to avoid leaks, with negative consequences on the reproducibility of the experimental results. We demonstrate the effectiveness of our approach by protein adsorption monitoring. The packaging materials do not interfere with the biomolecules and have a high chemical resistance. For future developments, wafer level bonding of the quartz capping onto the SU-8 walls is envisioned.

For biomedical microanalysis systems requiring implementation of optical signal generation and detection, we propose a package of VHDL-AMS functions to allow co-simulations of optical path, opto-electronic elements and associated electronics. This package contains a set of functions, which may be used for functional description of parts of microanalysis systems. An overview of simulation techniques shows that VHDL-AMS allows continuous-time simulation of polychromatic optical signals needed by the wavelength shifting nature of fluorescence. Indeed, directivity of optic path is well managed by VHDL-AMS using directional ports. By design, optical signals are easily simulated together with associated command and processing electronic circuits. Inspired by RF simulation techniques, the proposed description of polychromatic optical signals lies on a discretization of spectra. This format allows each optic band to be processed independently by models. The array data structure available in VHDL-AMS provides a compact form to device descriptions and to optical signal connexions. Fluorescence is modelled with absorbance and emission spectra, and optical couplings are described using results of geometric-optic analysis. A “spectral plug-in” has been developed, to be connected to output-power models of LASER-LED reported in the literature. Furthermore, a physical model of the CMOS Buried Double Junction (BDJ) detector has been described. Models of optic and electronic parts include a modulated LASER source, fibre optic, fluorochrom, BDJ detector and Constant Voltage Threshold (CVT) analogue-to-digital signal conversion. The system-level simulations, with Variable-Time Synchronous Detection (VTSD) are performed using the “Advanced-MS” environment. The validity domain of this approach as well as limitations of the available VHDL-AMS simulators (especially in terms of convergence and simulation time) are discussed.

We present proof-of-principle results regarding the possibility of micro-engraving Potassium Dihydrogen Phosphate (KDP) crystals using laser ablation techniques. The results of the work show that this technique can be used for realizing integrated optics and micro-optics components that are based on such crystals, one of the envisaged directions being that of integrated electro-optical modulators.

This paper presents the experiments we have performed to obtain freestanding SiO₂ and c-Si based microphotonic components by anisotropic wet etching of silicon (111) wafers. The process is simpler than surface micromachining. It requires only one grown or deposited layer and one mask for SiO₂ structure, or two masks for c-Si structures. Moreover, the technique provides plan-parallel microstructure with very flat (111) surfaces, useful for photonic components like micromirrors and waveguides. Movable SiO₂ and silicon-based micromirrors and waveguides with very smooth surfaces were obtained by anisotropic etching in a KOH solution combined with plasma etching. The possible applications of SiO₂ and silicon based freestanding structures include devices for optical communications and bio- or chemo-optical sensors.

We present a set of in-situ test structures for simultaneously determining residual stress (RS), Young's modulus (YM) and thermal expansion coefficient (TEC) of a film. Analytical models as functions of the displacement, geometry and material property of the test structures are theoretically derived for the task of extracting the film properties. This method utilizes available measurement apparatus and all the properties are identified and quantified on the same apparatus. The test structures consist of the measured film and the calibration film and are fabricated by a simple sacrificial-layer micromachining technique. The measured films made of undoped LPCVD polycrystalline silicon and the calibration film made of PECVD silicon nitride are used to demonstrate the effectiveness of the proposed method. The average calibrated residual stresses of undoped polysilicon films with deposition temperatures of 600°C and 620°C are 105± 5MPa and 240 ± 10MPa, respectively, and the corresponding Young's moduli are 170± 5GPa and 150 ± 5GPa. But the thermal expansion coefficient is approximately 2.7x 10^-6 average.

To validate the Front- To Backwafer Alignment (FTBA) calibration and to investigate process related overlay errors, electrical overlay test structures are used that requires FTBA [1]. Anisotropic KOH etch through the wafer is applied to transfer the backwafer pattern to the frontwafer. Consequently, the crystal orientation introduces an overlay shift. A double exposure method is presented to separate the process-induced shift from the FTBA shift. The process induced overlay shift can run up to 3 μm, large compared to the expected FTBA error (around 0.1 μm). The measured overlay distribution is 0.45 μm (3σ), this includes both waferstepper and process related overlay errors. The overlay distribution, corrected for waferstepper related overlay errors, like lens distortion, resembles the overlay distribution of the bulk micromachining (BMM) process; 0.26 μm (3σ). The procedures described in this work provide a quantitative method of describing the waferstepper and process related front to backwafer overlay errors.

In this paper we are going to present FEM calculations applied for laser bending of silicon microstructures and compare them with our experimental results. According to the mechanisms in plastic deformation of metals with laser radiation we performed calculations to find out, if there are similar mechanisms in forming of silicon. To model the laser heating up mechanism we have to take into account several physical effects like heat radiation or reflection of silicon for the used laser radiation. To transform the laser bending process into a FE model the boundary conditions include compromises and simplifications of the geometry and the energy input. In our calculations we modelled the laser beam as a moving heat source in order to get information about the temperature distribution, the temperature gradient and the heat flow in dependence on the position on the sample and the time. The calculated essentially higher temperatures at the edges of the structure compared to the middle of the structure, exceeding the melting point there, are in very good agreement to the melting areas observed at the edges in the experi-ments. After a number of consecutive scans we reach a balanced temperature field moving with the laser beam across the surface. The calculations revealed that there is a steep temperature gradient in the depth of the structure indicating a similar temperature gradient mechanism observed in forming of metals with laser radiation. Additionally we carried out temperature field calculations to determine the influence of the process parameters like the laser power, the velocity of the heat source, the material thickness or the position of laser treatment on the temperature field generated in the material. The results of the calculations are in very good agreement with our experiments. Next time stress field calculations are intended. At the moment there are not enough data on the plastic behaviour of silicon available to the authors in order to get reliable results.

In this paper, two matched microstrip line configurations for the excitation of magnetostatic wave resonators have been studied for optimizing the performances of a Magnetostatic Wave (MSW) Straight Edge Resonator (SER). The first transducer was designed for a band-stop and the second one for a band-pass resonator, both suspended on a silicon micromachined membrane obtained by means of wet anisotropic etching. It has been previously observed that the insertion losses of microstrip lines on silicon membrane for band-stop and band-pass MSW SERs are improved with respect to the same microstrip line structures realized on a silicon bulk substrate. For that reason the modelling of the microstrip lines has been optimized in view of their application in SER devices. The Microwave Office program, a powerful tool for the design of microwave planar devices, has been used. The theoretical S-parameters have been obtained and optimized by changing the geometry in the design of the transmission lines.

We report an analytical model for calculation of reflection and transmission coefficients of a Bragg reflector with periodic structure using transfer matrix method. Using explicit expressions for these coefficients, the reflectivity of the periodic structures for different pairs of layers and layer thickness was simulated. We investigate the reflectivity of the periodic structures consisting of following pairs of successive layers: SiO₂ /Si₃N₄ (low ratio of refractive indexes); poly-Si/ SiO₂ (high ratio), Si/air-gap (high contrast). The theoretical and experimental investigations of a particular periodic structure consisting of SiO₂/Au are also presented. Our method allows the rapid evaluation of reflectance of Bragg reflector with periodic structure.

We report on characterization techniques for microstructures using white-light interference microscopy. Capabilities include surface profilometry, integrated profilometry and lateral metrology for full 3D characterization, defect detection, profilometry of thin film structures, stroboscopic interferometry of vibrating samples, and real-time profile snapshots of moving MEMS devices.