International Journal of Computational Engineering Science

A digital/analog electrostatic actuating mechanism that can be applied for optical applications is presented. The mechanism is composed of electrostatic actuators with nails and clamped torsion beams. Based on the pull-in phenomena of electrostatics and the morph-shape bending of the actuators, the mechanism can be used to achieve digital/analog motions depending upon the applied voltage-range. Finite element model of the electrostatic actuator had been simulated to demonstrate the concept of actuation principle when the applied voltage is increased. Two functional micromirror devices were developed using Poly-MUMPs process to demonstrate the actuating abilities and its corresponding performances. Simulations and experimental results indicated that developed tilting micromirror could reach 2.5 ~ 4.2-degree digital tilting angle with 1-degree analog fine-tuning range. With fine-tuning function, the micromirror device is adaptive to the environmental drifts that could be applied for precise positioning in optical switching applications. The linear analog-tuning characteristic provides a solution for optical scanning applications. For the case of micromirror device that could achieve piston/rotation motions, the digital/analog mechanism is applied to realize optical phase/amplitude modulations. Experiments indicated that the micromirror could achieve 0.3 μm-displacement in piston and 0.8-degree angle in rotation.

In this study, a digital control system is developed for the microelectromechanical (MEMS) device - Variable Optical Attenuator (VOA). With the closed-loop control circuit, each VOA module implements the functions of power set point tracking and disturbance rejection. Moreover, this control system, with the device, entrusts the VOA module with leading performance, stability, reliability and fast dynamic response.

The development of micro-optical bench (MOB) technology as so far been limited by its reliance on polysilicon based elements which does not have good optical properties, and does not easily yield the spherical surfaces needed for refracting lenses. Polymers have shown large improvement in the recent years and could be a solution to hasten the development of MOB. We report here on the fabrication using polymers of converging and diverging refracting lens, with diameter ranging between 60 μm and 500 μm and with focal length as small as 100 μm. The polymer investigated where a photosensible cresol novolak (AZ9260), a photosensible epoxy resin (SU8) and a silicone (PDMS). In addition we have developed a phenomenological model and a physical model that elucidate the relationship between the fabrication parameters and the characteristics of the optical elements.

This paper describes a new type of optical switch, named as SWOMS (Self-latching Waveguides Optical MEMS Switch). The SWOMS is based on a novel micromachined bistable self-latching structure, which is fabricated on a SOI (silicon-on-insulator) wafer with a 35μm top silicon layer, and with polymer waveguides attached on it. Comparing to existing moving waveguide switches, SWOMS has some unique promising features such as gap-elimination and self-latching. Here, the structure, principle, and fabrication of SWOMS will be introduced.

This paper presents a micro machined tunable optical filter using micro-electro-mechanical-system (MEMS) technology. The tunable filter is comprised of Fabry-Parot cavity consisting of an in-plane-movable high reflection mirror by bulk micromachining and single mode fiber. The length of the cavity is tuned by adjusting the driving voltage to the comb drive actuator who controls the position of the mirror. This micro optical filter is silicon on insulator (SOI) based so that the process is simple and tuning range is great. The optical fibers are easily aligned with the mirror on the substrate thanks to the fiber groove obtained by the high-resolution lithography and deep etching process. The finesse obtained experimentally is 40 and 2.1 and the insertion loss is 12.0 dB and 6.6 dB corresponding to 140 μm and 35 μm original cavity length.

Tunable lasers have wide applications in DWDM systems to save inventory cost and to improve the optical network functionalities. The Microelectromechanical Systems (MEMS) technology has shown strong promise to miniaturize the conventional mechanical tunable lasers with adding merits of high compactness, high speed batch production and so on. In this paper, external cavity tunable diode lasers using MEMS movable mirrors and rotary gratings as the external reflectors are presented. One tunable laser of 2 mm × 1.5 mm is formed by integration of a surface-micromachined 3D mirror with a diode laser and an optical fiber. In addition, deep-etched structures such rotary gratings, circular mirror, microlens, and grooves for diode laser and fiber are illustrated to form widely tunable lasers.

In this paper, we describe a method for the 3D test of MEMS micro-components using optical interferometry. Utilizing optical interference, microscope optics, PZT nano-scanning and a CCD camera, the proposed technique can detect deformation and measure surface contour with precision of the order of nanometers. Application of the proposed technique is demonstrated by testing on two typical components: an accelerometer and a micro-mirror. The resulting interference fringes that are related to deformation of the micro-beam and the surface contour of the micro-mirror are analyzed by the fast Fourier transform (FFT) and 3-step phase-shifting algorithms. Experimental results from those components are given to demonstrate the feasibility of the proposed method for measuring 3D deformation and surface profiles of micro-components and to highlight the potential of the proposed technique as a tool for materials research.

Generally unaltered surfaces stemming from IC- or MEMS-production (Micro Electro Mechanical Systems) cannot be investigated with ESPI (Electronic Speckle Pattern Interferometry) due to the lack of any interference from the extremely flat surfaces of devices made of silicon. In order to enable ESPI for such devices additional "rough" layers can be added to the MEMS surfaces, while these relatively "thick" layers alter the mechanical properties of such small devices considerably. Utilizing a new surface preparation technique (Goeppingen Procedure^®) allows to create a nm-sized roughness onto the surfaces of MEMS, thus enabling interference originating from such altered surfaces and subsequently allowing ESPI.

Static ESPI on commercially available micro-sized tilt-sensors as well as read-write head of a hard disk drive showed that elastic deformations can be determined with a lateral accuracy in the μm-range and an axial accuracy in the nm-range, respectively. The static investigations allowed the identification of defect sensors in terms of quality assurance. Dynamic ESPI on MEMS showed different normal modes as well as the dynamic behaviour at the occurence of the first and the second harmonic.

Piezoelectric micromachined ultrasonic transducers for airborne and immersed applications in the frequencies from 20 kHz in liquid up to 750kHz in air have been simulated by finite element approach, fabricated and investigated. The basic element consisted of a oxidized and platinized silicon membrane coated with a 2 μm thick (100)-textured Pb(Zr,Ti)O₃ (PZT) thin film deposited by sol-gel techniques. SOI wafers have been applied to obtain a good definition of the silicon part of the membrane. The unclamping of the silicon membrane at the border increases drastically the coupling factor. For unclamped structures the membranes completely covered with top electrode show the highest coupling coefficient (k² = 5.6%). Immersed (in Fluorinert^TM) membranes show 7 times smaller quality factor, while the coupling factor k² remains the same. The obtained structures were enough sensitive to detect acoustic waves in air and in liquid emitted from the same type of elements at a distance of few centimeters. Good agreement between the experimental results (membrane deflection, admittance in air and in liquid) and FEA simulations has been obtained.

Structural vibration studies of various MEMS structures have revealed that whenever a suspended flat structure vibrates normal to a fixed substrate with a very small gap between the two surfaces, the squeeze film damping due to fluid present in the gap dominates the dissipation mechanism by orders of magnitude compared with other losses. Since the quality factor is a critical parameter in the design of MEMS devices and it depends on damping, a careful evaluation of the squeeze film damping is necessary. The most often used formulas for evaluating this damping, due to Blech and Griffins, are based on the linearized Reynolds equation. These formulas are applicable for small amplitude oscillations. In this paper, we consider all nonlinear terms in the governing equation of the flow between the plates and study the effects of these terms on the damping characteristics. We show that as the amplitude of vibration increase, the damping force increases faster than the spring force of the fluid and, therefore, the cut-off frequency changes nonlinearly.

The present work is to show the development of micropower systems or power MEMS characterized by thermal, electrical and mechanical power density 1~20 Watts in sub-centimeter-sized packages. Three kinds of typical micro power systems, namely, the micro-gas turbine engine, the MEMS rotary micro engine, and a micro thermoelectric system, are described in this paper. A novel microthermophotovoltaic (micro-TPV) system, which is being developed in NUS, is also introduced in this work. The system uses hydrogen as fuel and is able to deliver electrical power in the order of watts in a package less than 1 cubic centimeter in volume. The main components of the system are a heat source, a selective emitter, and a photovoltaic (PV) array. The performance of the system is largely affected by the materials of the emitter and the PV cells. When the emitter is made of Co/Ni-doped MgO, and the PV cells are made of GaSb, a 4.4 W electrical power output can be expected.

In this paper the design, fabrication and testing of the capacitive micro accelerometer with Silicon On Insulator (SOI) approach is presented. The beam location with respect to a rectangular mass is optimized, using finite element analysis (FEM) to minimize cross axis sensitivity. It is demonstrated that a simple KOH etching with the addition of the tert-butanol can be easily adopted to fabricate the accelerometer structure without any convex undercutting effects. The devices are tested by electrostatic actuation.

In the present work, we report a novel process for fabricating suspended silicon dioxide micro-structures inside the anisotropically etched cavity formed in (100) silicon wafers. Using this new process, the moving parts are "recessed" in the substrate which can be packaged and handled easily compared to non-recessed structures. In the fabrication process, spin coated liquid photoresist is used. There is a common problem of thinning of photoresist on convex edges of the cavity during photolithography steps. As a result, silicon dioxide is etched away from these edges. During subsequent anisotropic etching of silicon to release the microstructures, the unprotected convex edges are also etched resulting in failure of the process. To overcome this problem, two different methods are used. In the first method, high viscosity positive photoresist (Shipley STR-1045) is used and the multiple coatings are carried out to cover the convex edges adequately. This protects the oxide on convex edges in buffered hydrofluoric acid. In the second method, standard low viscosity positive resist (Shipley 1400-27) and negative resist (E. Merck N60) are used and the convex edges are diffused heavily with boron (P⁺). Recessed microstructures have been successfully fabricated using both these process.

This paper presents a novel z-axis accelerometer with perfectly aligned vertical combs fabricated using the Extended Sacrificial Bulk Micromachining (ESBM) process. The z-axis accelerometer is fabricated using only one (111) SOI wafer and two photo masks without wafer bonding or CMP processes as used by other research efforts that involve vertical combs. In our process, there is no misalignment in lateral gap between the upper and lower comb electrodes, because all critical dimensions including lateral gaps are defined using only one masks. The fabricated accelerometer has the structure thickness of 40 μm, the vertical offset of 15 μm, and lateral gap between electrodes of 4 μm. Torsional springs and asymmetric proof mass produce a vertical displacement when an external z-axis acceleration is applied, and capacitance change due to the vertical displacement of the comb is detected by charge-to-voltage converter. The signal-to-noise ratio of the modulated and demodulated output signal is 80 dB and 76.5 dB, respectively. The noise equivalent input acceleration resolution of the modulated and demodulated output signal is calculated to be 500 μg and 748 μg. The scale factor and linearity of the accelerometer are measured to be 1.1 mV/g and 1.18 % FSO, respectively. The measured bandwidth is more than 100 Hz.

The present work is an investigation and characterization of a new technique for etching and masking lithium niobate (LiNbO₃) to realize high aspect ratio structures. LiNbO₃ is a single crystal, optically clear (from 350 nanometer to 5 micrometer wavelength) piezoelectric and electro-optical material. It is inert to most reactants and has a high Curie temperature. These properties allow LiNbO₃ to be used as a sensor or actuator in harsh environments or as an optical modulator. Multi-level lithium niobate deep etching techniques are currently unavailable or limited. The present work uses a chrome gold mask with a solution of hydrofluoric acid and nitric acid at 80 °C to etch the LiNbO₃. The novel wet etch method developed yields an etch rate of 30 micrometer per hour on the -z face and less than 250 nm per hour on the +z face. In the experimentation done with this research trenches 80 micrometers deep were fabricated. Experimental etch and results are detailed.

Titanium nitride (TiN) thin films have low electrical resistivity, good chemical and metallurgical stability, and exceptional mechanical properties. As such, we are interested in exploring TiN for use as mold material for micro-and nano replication. Focused ion beam (FIB) technique was successfully used to fabricate sub-micron sized pattern on a TiN/Si(100) wafer. This mask-free fabrication technique takes advantage of the kinetic precision of FIB; the energy of ions used was 40 KeV. The width and depth of each trench in the TiN mold are 390 nm and 280 nm respectively.

Electroless nickel plating is an important process in the fabrication of metal microstructures on silicon substrates. Adhesion of the metal film to the substrate is a key parameter. We report a study of the adhesion of electroless nickel plating on polished silicon for different surface treatments (prior to plating), substrate areas and plating durations. Three different surface treatments considered are: mild etching, palladium activation and nickel activation. Adhesion strength in excess 9.8 × 10⁷N / m² has been obtained. Adhesion requirements for using nickel plating for masking the silicon substrate during anisotropic etching is also discussed.

A new process for fabrication of piezoelectric micro-cantilever arrays with PZT thin film for micro or nano range actuation has been developed. By choosing different DRIE etching process, 2 kinds of microcantilever can be fabricated and also we can almost fabricate membrane PZT cantilever with 100% yield, which is impossible in other normal fabrication process due to the over etching of the silicon resulting in some cantilever broken. Film annealing temperature and time critical to the preparation of the sol-gel PZT thin film. The fabrication process of micro-cantilever arrays in planar structure will be presented. Key issues on the fabrication of the cantilever are: the compatible etching process of PZT thin film, the compensation of thin film stress in all layers to obtain a flat multilayer structure.

This study is on a new approach for fabrication of poly-Si thin films. Aluminum-induced crystallization of a-Si film has been achieved by thermal annealing only at around 400 °C. The Experimental results reveal that the Al on top of a-Si arrangement has more evident effect in crystallization enhancement than that with Al under a-Si, and the resultant poly-Si films show preferred (400) crystal orientation. It is verified that aluminum can cause lateral crystallization of a-Si film. No preferred orientation was noticed from lateral crystallization samples.

A novel micropropulsion system is described for high-accuracy station keeping, attitude control and speed adjusting of microspacecraft. The proposed solid propellant microthruster is composed of two layers bonded together. One layer is a silicon layer, which contains a microchamber, a micronozzle and a 30-micron slot. The specific solid propellant is loaded in the microhamber for combustion. The convergent-divergent micronozzle is used to accelerate the combustion gas to produce thrust. The slot is employed to insert the special ignition wire to ignite the solid propellant. The other layer is a glass layer, which is bonded onto the silicon layer to form 3-D microthruster. Numerical investigations have been carried out before the fabrication. The thrust ranging from 1 mN to 10 mN is produced depending of on different geometries. Single microthrusters and microthruster layers have been fabricated successfully using MEMS technologies.

In this paper, we report the sputtering of SiO₂ as a viable low temperature process for MEMS applications. Very homogenous films were prepared on Si substrate using RF diode sputtering of SiO₂ target in argon atmosphere. The effect of target to substrate spacing, sputtering pressure, RF power, and substrate cooling were investigated. The IR transmission spectra and etch rate of silicon dioxide in buffered hydrofluoric acid were measured and these were compared with those of thermally grown silicon dioxide. Microstructures of sputtered SiO₂ film were fabricated using bulk micromachining process. The use of positive photoresist as sacrificial layer in surface micromachining technology was explored. The substrate heating was found to be the limiting factor for high rate sputter deposition.

We have developed two fabrication routes for functional micro devices using SU-8/nanoparticle composites. In the first route, patterning of a 0.5% nanoparticle/SU-8 composite resulted in magnetic and luminescent polymeric microstructures. In the second route, a 42% nanoparticle/SU-8 composite was patterned followed by sintering to obtain free standing ceramic microstructures with aspect ratios as high as 16.

The concentration of photoacidgenerator (PAG) in SU-8 determines the UV absorption and, therefore, is a limiting factor of the applicable SU-8 thickness. The motivation of this work is to improve SU-8 process control and expand the application scope of SU-8 by modifying its PAG concentration. In this paper we present the experimental results on lithographic properties of SU-8 as the function of PAG concentration (varying up to 2 orders of magnitude). It includes determining the minimum bottom dose and minimum effective energy density for x-ray and UV lithography of SU-8, respectively, and the UV absorption spectra of SU-8. It is fund that as the PAG concentration reduced, SU-8 has lower sensitivities in UV and x-ray lithography, and lower UV absorption coefficients. By using PAG diluted SU-8 taller microstructures with vertical sidewall can be obtained with UV lithography. Based on the large difference in lithographic sensitivities between normal and PAG diluted SU-8, we have developed a new process concept for making 3D microstructures. The 3D microstructures fabricated based on this new process, including microcantilever and microchannel, will be presented.

In this work, an electroplated Ni material made from sulfuric acid-based plating solution has been studied. Differential scanning calorimetry (DSC) technique was used to study the stability of plated Ni at elevated temperatures. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to examine the microstructural changes of plated samples as a function of annealing temperature. Microhardness tests were performed to study the effects of the evolved microstructures on surface mechanical properties. The activation energy for the grain growth was determined by using isothermal kinetics analysis.

In order to improve the performance of LIGA/MEMS components at high temperature, it is crucial to understand the grain coarsening processes of electroplated Ni materials at elevated temperature.

Relaxor ferroelectric (1-x)Pb(Zn_1/3Nb_2/3)O₃-xPbTiO₃ is attractive for many electromechanical transducer applications due to its very large piezoelectric responses, and high electromechanical coupling factor. An oriented PZN-xPT film is particularly desired to achieve further enhanced piezoelectric performance. However, it is difficult to obtain pure ferroelectric perovskite phase in a PZN-xPT thin film because of the preferential formation of detrimental pyrochlore phase.

In this paper, perovskite PZN-xPT thin films were prepared by a sol-gel method on (100) Si substrates. A (100)-oriented perovskite LaNiO₃ (LNO) thin film was deposited as both the bottom electrode and seeding layer; and a ZrO₂ film was deposited as a buffer layer between the LNO film and the Si substrate. X-Ray Diffraction (XRD), and Scanning Electronic Microscopy (SEM) were used to examine the structure, orientation, and morphology of the PZN-xPT thin films. The dielectric and ferroelectric properties of the films were measured with an impedance analyzer and a standard ferroelectric testing system, respectively. The results showed that perovskite structure with (100) orientation was successfully obtained in the PZN-xPT films. The film exhibited a typical ferroelectric P-E hysteresis loop with a high remanent polarization.

Design technology and characterization of new GaAs island based Micromechanical Thermal Converter (MTC) device are presented. The MTC device introduced consists of pHEMT as a microwave heater and thin film polySi/Ni resistor as a temperature sensor monolithically integrated on polyimide-fixed 1 μm thick GaAs/AlGaAs island structure. The preliminary experimental results in the device electro-thermal conversion evaluation are demonstrated.

AlN thin films were grown on Si(100) and Al/Si(100) substrates by pulsed dc sputtering system using 99.999% purity aluminum as target, and Ar+N₂ gas mixture as precursor. The impact of deposition parameters on material properties has been investigated has been investigated. A good correlation between film crytallinity and dc power, as well as gas pressure, was addressed by x-ray diffraction, and verified by scanning electron microscope (SEM). It is found that highly c-axis oriented h-AlN can be obtained at low gas pressure and low deposition rate. For AlN on Al/Si(100) substrate, micro-crack was observed, which was assigned to the large thermal stress between AlN film and Al layer. Crack-free surface has been achieved by reducing the deposition temperature. The deposition mechanism of AlN deposition is discussed.

The self-assembled nanostructured aggregates with various morphologies, including spherical micelles, worm-like micelles, vesicles and lamellae, have benn observed from the BAB triblock copolymers in water. Here, the polymers used are Polystyrene(PS)₄₃-b-Poly(ethylene oxide)(PEO)₄₅-b-PS₄₃ copolymer with Mw/Mn = 1.48 prepared by ATRP and PS₃₉-b-Poly(4-vinylpyridine)(P4VP)₉₈-b-PS₃₉ copolymer with Mw/Mn = 1.15 synthesized by RAFT. The size and shape of the aggregates are controllable according to some tunable parameters of systems, which affect the balance between three of the major forces acting on the system. These include the stretching of the core-forming blocks, the intercoronal interactions, and the interfacial energy between the solvent and the micellar core. The multiple morphologies were obtained by altering the solvents, solvent composition, copolymers, pH, concentrations, and so on. In addition, the second aggregation behavior of spherical micelles, spherical vesicles, and worm-like micelles was interestedly concerned. It was found that the second aggregation behavior the different complexity for different primary aggregates. For symmetrical primary aggregates, such as spherical micelles and vesicles, the second aggregates appeared symmetrically spherical. In contrast, for unsymmetrical worm-like primary micelles, the second aggregation tended to have unsymmetrical shape. The BAB chain architecture was molecularly suggested to be responsible for the second aggregation.

A MEMS varactor using torsional beams for actuation is proposed. Analytical expression for electrostatic torque developed is derived. The structure is compared with existing structure for dynamic range and actuation voltage. A compensator is designed to improve the transient performance of the device.

The Mimosa Pudica is an action plant that closes its leaves when given a stimulus. The plant integrates both sensing and actuating mechanisms, and the distinctive motion is about a hinge-like point, the pulvinus, making the characterization of the motion attractive. In this project, experiments were set up to measure the characteristics of the plants in the goal to estimate the possibility to produce micro-actuator based on a similar principle. The signal speed, the sensitivity, the actuator speed, the power, the torque produced by the plant were measured by using different sensors. The results showed that the torque is dependent on the diameter of the pulvinus and that actuator could reach a top angular velocity of 1 rad/s. We developed a phenomenological model to describe the behavior of the plant that could match experimental results and propose an original physical description of the mechanism inside the plant by considering a phase transition behavior instead of the classical ion channel model. Finally, the plant actuator energy density is also compared with other known micro-actuators and the possibility to use the plant as a micro-actuator is discussed.

PZT(PbZr_xTi_1-xO₃) thin films have been locally grown by means of sol-gel deposition and local anneals on microhotplate. The microhotplate was based on a tantalum silicide filament (Ta₅Si₃) formed on stress compensated SiN/SiO₂ membrane. On this filament, a passivation layer of SiO₂, a layer of Ti/TiO₂ and a bottom electrode of Pt were deposited. Due to the low heat conductivity of the membrane, crystallization of the PZT film occurs exactly on the resistor filament. The formation of crystalline, i.e. perovskite PZT was verified by means of X-ray diffraction. A random PZT texture has been observed.

A general theoretical model using the coupling effect between the torsion and bending is presented in this paper, and which characterizes the static properties of the electrostatic torsional micromirror, especially its pull-in effect. The pull-in effect is investigated specifically to predict pull-in voltage, pull-in angle, and pull-in displacement, which highly depend on the electrode size and position, and ratio of the bending and torsion effect of the torsion beam. The ratio of the bending and torsion effect plays a key role in the pull-in phenomena. It also determines the instability mode of torsional micromirrors dominated by either the torsion or bending effect. Then, a group of torsional micromirrors is fabricated using three-layer-polysilicon micromachining process and measured using an optical projection method to verify the static actuation relation and pull-in-effect respectively. The experimental data are processed analyzed, and the theoretical analysis is in good agreement with the experimental results.

The objective of the paper presented here is to develop and demonstrate a MEMS silicon-based tunable capacitor for RF communications application. The tunable capacitor is made of single crystal silicon based on silicon-on-insulator (SOI) technology, and that has a continuous tuning range in excess of 300%. The electrical capacitance model will be provided here in details to demonstrate tuning characteristic and RF performance of tunable capacitor.

A new thin film technique is proposed and demonstrated in this paper to prevent the notching effect on silicon on insulator (SOI) wafer micromachinig. SOI wafer provides decisive features. However, the notching effect or undercutting due to the charges built up at the surface of the buried insulation layer degrades the structures and performances of the devices. In this paper, a thin oxide film is introduced combining with multiple steps of etching to prevent the notching effect. To verify this idea, a mask with trenches from 0.4 to 20 μm was designed and the etching was carried out on SOI wafer with 35 μm device silicon layer. The etching result showed that the approach proposed is very effective on notching effect.

The primary problem of large intrinsic compressive stress induced during the deposition of amorphous carbon (a-C) films prepared by Filtered Cathodic Vacuum Arc (FCVA) technique has been overcome by preparing the films in conjuction with high substrate pulse biasing. However, it has been observed that the stress reduction is achieved by sacrificing the mechanical properties such as hardness and Young's modulus of the films. Hence the mechanical properties of the films were studied as a function of substrate bias voltage. In addition, to demostrate these low stress films, one-micron thick, a-C membranes were fabricated by photolithography technique together with deep reactive ion etching (deep RIE) and wet KOH etching.

The super-resolution process allows reducing the size of clear mask features in x-ray lithography by appropriately choosing exposure and development parameters. The proximity gap between mask and wafer is a parameter that has great impact on process latitude. A method is found to monitor the proximity gap experimentally. Experiments confirm the validity of our simulations.

This paper presents a single-wafer, large-displacement electrostatic vertical motion actuator, using the extended sacrifical bulk micromachining (SBM) technology. The driving scheme is a torsional lever mechanism that achieves a large vertical displacement, which is achieved using a low driving voltage by novel small-gap vertical combs. The extended SBM process is used to fabricate combs that have different heights. These combs achieve about 10 μm vertical motion at 60 volts. The vertical displacement on the opposite end is 30 μm by the 3:1 lever ratio. A new process for electrode isolation is also developed for hign aspect ratio microstructure. The process uses doping sidewalls for an effective PN junction. The developed process is used to fabricated a single on-off optical switch as well as a 4×4 array switches. The switches use shutters for optical switching. The fabricated optical switch has a 2.3 degree of tilt angle at a 60 V driving voltage. The 2.5 degree tilt angle gives 30 μm displacement at the optical shutter. Optical signal off to on time is 0.09 ms and optical signal on to off time is 0.10 ms, which is sufficiently fast for optical switch applications.

This paper presents the development of a reduced-order macro-model for a two-axis electrostatic torsional micromirror using analog hardware description language (AHDL). The proposed macro-model permits extremely fast simulation while providing nearly FEM accuracy. This enables the user to investigate the close-loop controlled global system level performances at acceptable computational cost.

So far the verification of specific bacteria is time consuming and costly. The reason is the neccessity for highly specialised laboratory equipment and the requirements regarding clean-room facilities ensuring environments free of any germs. Additionally growing bacteria in equivalent petri dishes may require quite some time until a reasonable number is grown sufficient for further evaluation. For many bacteria and even viruses alternative processes for multiplication have been developed, basically relying on the so called Polymerase Chain Reaction (PCR). We developed the Goeppingen GeneReactor, a microsized system (MEMS) for PCR as a low cost device, that can be used without any clean-room facilities, while additionally a device for electrophoresis is added as a tool for analysis. Thus this system can be used as a throw analysis tool, i.e. specimen containig the required bacteria or viruses could be preparated and investigated in every physician's pratice. It should be noted, that even tiny amounts of starting materials are sufficient, since the whole system is no large than a human finger-nail and the PCR allows to multiply the number of desired genes by a factor of 10³ to 10⁶ within 10 to 20 heating cycles.

Chemical reactions can be very complex and frequently produce undesired side products within short time spans. Investigation of such reactions necessitates in-situ measurements for analysis. We present a novel micro-reactor design enabling non-invasive and spatially highly resolved in-situ reaction analysis using Raman spectroscopy. The reactor consists of a stainless steel base containing milled channels covered with anodically bonded pyrex glass. The educt flow rate is finely controlled by a motor-driven feed pump. Monitoring of an exemplary test reaction by Raman spectroscopic means was achieved by recording spectra at various discrete sampling points along the reaction channel. The glass window allows visual observation of the channels by optical microscopy and does not affect, in contrast to infrared spectroscopy, the Raman spectroscopic signal. Taking Raman spectra along the reaction channel at different loci enabled us to determine the reaction kinetics of a fast chemical reaction.

Applying thin film MEMS technologies threedimensional reference structures for spatially high resolving optical imaging and spectroscopy techniques were manufactured containing non-transparent defects of different lateral and axial extention and being located in various heights within the samples. This special manufacture was enabled using thin films of resist as layers in between the defects layers, as well as applying a modified "single mask process", the geometrical arrangement of the defects being distributed on different quadrants of the "mask" according to their axial height in the subsequent reference structure. Minimal distances of about 600 nm in between two defect layers could be achieved.

The paper deals with the development of silicon tools and an appropriate hot embossing technology for polymers. With this technology, high quality embossing of optical or fluidic structure for high precision requirements in a batch process is possible thereby reducing system costs. Possible usage is the production of Micro Electro Mechanical Systems (MEMS) for optical or fluidic applications. This could be sensors for chemical analysis of liquids or BioMEMS. Further promising applications are multifunctional printed circuit boards (PCB) or micro cooler. Up to now for coarser dimensions the use of conventional made (e.g. miling) steel tools is common. For forming of smallest structures down to the sub-micrometer range with excellent surface roughness LIGA technology is applied. However, in order to reduce the system costs LIGA tools shall be substituted by silicon tools. Deep reactive ion etching (DRIE) is used to fabricate such an embossing tools allowing complex geometrical figures. For fluidics or optical applications the tool structures have to show a tapered (positive) profile and sufficient low roughness. Roughness can be minimised by further oxidation and etch steps. The hot embossing experiments which will be presented show the capability of the optimised DRIE technology for the aimed application field.

This paper describes a micro capacitive pressure sensor for hydrostatic tank gauging (HTG), an emerging way to accurately gauge liquid inventory and to monitor transfers in tank farms. Since industrial storage vessels are huge, the sensing element must be sufficiently thick to withstand the large pressure inside the tanks. However, a thick diaphragm is insensitive to the relatively small pressure changes brought about by variations in the fluid head. To detect small pressure changes in the presence of a high constant load, a novel three-plates structure that introduces an additional plate between the two electrodes of a parallel plate capacitive pressure is proposed. A boss ring etched below the thick top plate, which serves as the sensing element, will come into contact with the middle pate and cause it to deflect when the applied pressure crosses a pre-determined threshold. Pressure is measured by monitoring the change in capacitance between the middle plate and the insulated substrate. As the middle plate is constructed as a cantilever, it magnifies the small deflections in the diaphragm and thus enabling small changes in pressure to be detected. Simulation results indicate that the sensitivity of the proposed structure is comparable to conventional parallel plate capactive pressure sensors.

MEMS (Micro Electro Mechanical Systems) products are being spread from laboratory to industries. But Silicon-based MEMS products are usually expensive and not suitable for low cost production. Hence, there is an emerging need in terms of cost effectiveness to transfer MEMS from silicon-based materials to other materials, such as glasses and polymers. Micro hot embossing is expected to be a novel technique for producing MEMS components/products with low cost, and will potentially find wide applications in micro fluidics, biomedical and micro optical areas. In this paper, a hot embossing instrument is illustrated and is used for the process development of micro/nano structure forming with polycarbonate (PC) and Polyetheretherketone (PEEK) by using the Nickel mold. Fabrications of micro vertical reflecting mirrors and cantilevers for an 8×8 optical switch have been carried out, replication of micro grooves and pyramid cavities with nanometer precision for passive alignment of optical fibers and micro ball lenses have been performed as well. The results show that hot embossing is a promising technology for cost effective micro/nano fabrications of MEMS.

This paper presents the design, realization and simulation of a novel polymer based check-valve micropump actuated by piezoelectric disc. Comparing with silicon substrate, polymer materials have such advantages as flexibility, chemical and biological compatibility, 3D fabrication possibility and low cost in material and mass production. Laser micromachining technology and precision engineering techniques were used to fabricate the prototype with the dimension of Φ20mm×5.2mm. Result of preliminary experiments on fusion bonding between polyimide and polycarbonate are also presented. Due to the small difference between their glass transition temperatures (T_g) the polyimide and polycarbonate could be bonded together relatively easily. A special fixture for the bonding process has been designed and made to control the lateral and vertical expansion less than 1.5%. Using DI water as the pumping medium, the presented micropump is expected to achieve self-priming, bubble tolerance and low power consumption and a flow rate of 30μl/min at the resonance frequency of 300Hz. A planar format micropump will be delivered based on this presented successful design for mass fabrication.

MEMS based heatuators are being used extensively for actuation purpose. The conventional heatuators have different arm widths while this paper proposes a variant design that has equal widths but unequal resistances. The new design brings in the advantages of faster response and greater deflections for similar condition. The heatuators have been simulated using the coupled-fied element SOLID98 of the finite element analysis software ANSYS.

This paper presents a new preparation scheme of monolithic pyroelectric thin film infrared sensor. The sensor can be prepared directly on readout circuit and its electrode can be connected to the readout circuit through a via. PbTiO₃ thin film is used as pyroelectric material. Porous SiO₂ thin film is applied onto silicon wafer to improve the thermal isolation of the pyroelectric layer. Copper interconnection is used in readout circuit to solve the problem that aluminium interconnection can't endure the annealing temperature of PbTiO₃ thin film.

Two-dimensional thermal analysis of multi-layer thin film pyroelectric infrared detectors is performed according to the structure and test conditions of detectors and the temperature distribution of detectors is obtained. Result shows that the insulation layer of multi-layer film pyroelectric infrared detector can effectively reduce thermal flow from pyroelectric layer substrate and the response of detector increases with the increasing of insulation layer thickness; when the thermal conductivity of insulation layer is lower than of air, its performance is better than micro-bridge structure.

In this paper, we have successfully modeling a vertical motion electrostaitc comb drive and proof it's efficiency by using existed experimental data. A commercial 3-D MEMS Simulator was employed to stimulate the static levitation of vertical comb drive. Note that, by gradually increasing the dc bias voltage, each simulation process is either converged slowly or even enters the divergence stage. Hence, the 3-D simulator is degraded in simulating vertical electrostatic comb drive in full input range. In the present modelling method, Maxwell 2-D solver was employed to calculate the comb finger capacitance at different z positions firstly. Second, A 6^th-order curve fitting was used to extract the capacitance function, C(z), and the unit electrostastic force function, dC/dz, was obtained by taking derivative of capacitance function. Finally, a dynamic system model block diagram was established in Matlab Simulink program environment. A set of ideal geometry parameter was selected to verify the accuracy of our model. The simulation results were compared with the experiment results, and a 50% error was observed. After replaces the ideal geometry parameters with actual geometry parameters, the error was reduced substantially, within 10%.

Electrical impedance analysis and energy dissipation methods are the two main methods to evaluate the damping behaviour of the quartz crystal. The motional resistance of the quartz crystal, which can reflect the quality factor (Q), is monitored in the electrical impedance analysis and the dissipation factor (D), which is inversely proportional to the Q, is measured in the energy dissipation methods. A comparison of the Q from electrical impedance analysis, termed as "electrical Q" and from the energy dissipation methods, termed as "mechanical Q" is presented in this work. The damping behavior of 5 MHz QCMs subjected to polymer caotings are studied by both methods. The resonant frequency, f, and Q before and after polymer coatings are measured using the network analyzer and a QCM-energy dissipation (QCM-D) instrument. The frequency shifts from both methods are quite comparable and the changes of the dissipation factor and the Q factor are also similar. Possible factors accounting for the Q change such as mass loading effect, evenness of the polymer coating, surface roughness of the crystal, are analyzed. The thickness range of the coating over the QCM can be used as a platform for bio sensing is also discussed.

A micro thermocycling chip has been developed, which is able to achieve high heating and cooling rates of over 16°C/s and 9.6°C/s respectively using the induction heating method. The heating element of the micro thermocycler was fabricated through electroplating on glass. SU-8 and Polydimethyl-siloxane (PDMS) are used to form the reaction chamber. DSP base servo controller was selected for close loop control the reaction chamber temperature. The thermocycler chip's properties, such as non-contact heating method, rapid cycling speed and PC control, make it suitable to integrate into clinical molecular diagnostic devices and point-of-care devices.

Low temperature bonding of two silicon wafers with significant high bond strength has been prepared successfully using sol-gel coating as intermediate layer. The effects of bonding temperature, solution aging time and spin speed on bonding quality have been investigated by a full 2³ factorial design. Under the 75% confidence level, the statistic result shows that only the interaction effect between bonding temperature and spin speed is significant. Design of experiments (DoE) is used to study the effects of key parameters on bond strength, and bonding mechanism are discussed. The possible reason for the observed high bond strength is the absence of absorbed water on the smooth coating surface, which results in the direct condensation reactions between OH groups to form strong Si-O-Si bonds even at low temperatures.

Ni₂MnAl Heusler alloy is one of the promising materials for the shape memory effect. It has been reported in literature that the magnetic shape effect is observed only when this alloy is in L2₁phase. The appropriate processing parameters to achieve this phase in this alloy, is the subject of our study in this report. The results of our investigations of the structural and magnetic property changes at various stages of processing are reported here. Differential Scanning Calorimeter and dc magnetization measurements have been used to probe structural and magnetic phase transformation of the material after the heat treatment. The structural analysis has been carried out by X-ray diffraction mehod.

Synthesis of alkanethiolated gold nanoparticles, which formed spontaneous ordering of larger nanoclusters, has been successfully demonstrated. These three-dimensional nanoclucters containing thousands of gold nanoparticles functionalized with 1, 6-hexanedithiol have interesting properties, which were characterized using High Resolution-Transmission Electron Microscopy (HR-TEM) coupled with Energy Dispersive Spectrometry, Scanning Electron Microscopy and X-ray Photon Spectroscopy (XPS). These results are valuable for further exploration into the nanoclusters' electronic characteristics as well as to understand the thiol chemisorption and physisorption processes onto various substrates such as glass and silicon.

Conventional SU-8 lithography process for fabricating microfluidic devices ofthe uses silicon or glass as wafer materials. Since silicon and glass are hard and brittle, drilling fluid access holes or dicing the wafers into individual devies are difficult. We investigated the use of polymethylmethacrylate (PMMA) as a new wafer material. PMMA, an amorphous thermoplastic, was chosen for being easy to drill or cut, biocompatible, transparent, and much cheaper than silicon or glass wafers. Moreover, is thermal expansion coefficient ideally matches that of SU-8. PMMA poorly resists solvents, and has low glass transition temperature (105°C). Thus, the conventional process needed to be modified. The wafer was only cleaned with isopropyl alcohol and deionized water. The baking temperature was lowered to 90°C. In addition, a "base layer" of SU-8, helping to achieve a high quality structural pattern, was coated before coating the actual structural SU-8 layer. A Tesla valve, a non-moving part microfluidic valve, was successfully fabricated in SU-8 using thr presented process,. However, the PMMA wafer bowed ue to the thermal residual during baking steps. Despite the bowing which can be solved by increasing wafer thickness, we conclude that PMMA is a promising wafer material for a SU-8 process.

The amorphous carbon films prepared by filtered cathodic vacuum arc (FCVA) deposition system are superior in nature with very smooth surface morphology, relatively high hardness, favorable tribological behaviour and excellent bio-compatibility. These exceptional qualities make them suitable for many device applications. However, the superior quality films prepared at relatively lower substrate bias such as -80V exhibits high compressive stress and thus limit the thickness of the film. This constraint is overcome by stress reduction, which is achieved by preparing the film in conjunction with high substrate pulse biasing.

Free-standing Diamond-like Carbon (DLC) micro-cantiliver arrays were successfully fabricated by a single photolithography step. The relatively thick (~1μm), smooth (R_ms ~0.75nm), low stress (<300MPa) DLC films that exhibits low friction (<~0.08) and wear rate (~10^-9mm³/N-m), were deposited, on patterned highly doped n-type Si <100> substrates, by the FCVA deposition system in conjunction with high substrate pulse biasing of -5kV, 900Hz and 30μs. The undecutting of the microstructure was carried out by anisotropic wet etching of Si in 40 wrt% KOH at 23°C for 31 hrs. The SEM image of the free-standing DLC micro-cantiliver arrays reveals that the maximum transverse deflection of the cantilever at the free end is quite low. The quantitative measurements of deflections were also carried out using an optical profiler to verify.

In this work , a tunable resonator is designed. Using the voltage actuators, the fundamental resonance frequency of the resonator is varied. The voltage applied to the tuning combs results in change in the stiffness of the folded beam suspension, which in turn changes resonant frequency. The resonator is modeled in circuit simulator using voltage controlled current sources. The effect of change in stiffness (k_c) is included to model tunable resonator. A voltage-controlled oscillator is designed using the tunable resonator.

We demonstrate a novel rotary micromirror for fiber-optic switching. A very simple fabrication process which uses SOI wafer and DRIE technology has been employed to micromachine this electrotastically actuated vertical mirror. Based on this one-mask process, 2N-switch-architecture crossconnects with all the components, inlcuding optic fiber couplers electrostatic comb drives and reflective vertical mirrors, has been integrally fabricated on a monolithic silicon substrate.

It is highly desirable to develop a phosphine-free recyclable heterogenous catalytic system without the use of expensive and air-sensitive basic phosphines for palladium-catalysed coupling reactions. Nano-palladium catalysts for example, in various stabilised forms have been extensively explored as potential alternatives to achieve a higher catalytic activity. In line with the great interest directed towards the development of microfabricated chemical systems for a variety of chemical and biological applications, we demonstrate here a microreactor based on microfluidic channels on glass chips for the continous flow organic synthesis using immobilised nano-palladium. The palladium colliods were immobilised on the inner-walls of the microchannels via an intermediate organosilane monolayer. The covalent attachment of colloidal palladium provides minimum leaching of the catalyst. The Suzuki coupling of an aryl halide and an organoboron has been used a model system to investigate the performance characteristics. The reaction affords an excellent yield, a higher turnover rate and the ease of catalyst recycling. Similarly, the approach can be applied to other palladium-catalysed syntheses, such as Heck-, Sonogashira-, and Stilles-type coupling reactions.

This paper purposes a very simple and reliable fabrication process foar a silicon capacitive microphone, the two electrodes of the condenser microphone are: a thin p++ silicon membrane fabricated using an optimized diffusion process, and a thick -30 μm - top electrode, processed also on a silicon wafer. Isolating and metal layers assure the gap between those two eletrodes. The bonding between electrode's wafers is performed using an Au-Si eutectic wafer-to-wafer bonding techniques. The thinning of top-electrode was made in the same step of the process as the etching of silicon diaphragm. The concept of fabrication process was to avoid the sticking of thin diaphragm to top electrode during different wet process. Different design with different size of diaphragm was fabricated using this process. The resulting capacitance was in the range of 1.85-3.5 pF.

This paper presents a bulk micromachined check valve with very high frequency and extremely low leak rates. The valve is designed to have a hexagonal orifice, a hexagonal membrane flap and three flexible tethers. The three elbow-shaped flexible tethers are used both to secure the membrane flap to the valve seat and to abtain a large flap displacement in the forward flow direction. SOI wafer and DRIE technology are used to implement this micro valve. A very simple farbication process has been developed, and only two photolithographic masks are employed. Preliminary testing on a 1.5 milimeters size check valve shows that a maximum flow rate (DI water) of 35.6ml/min was obtained at pressure drop of 65.5kPa and negligible leakage rate in the reverse flow direction observed at pressure up to 600kPa.

Convex and concave nano-pyramid Arrays (NPAs) with an areal bit density of 258 Gbits/in² has been demonstrated by means of scanning probe lithography (SPL) and wet ecthing on the (100) silicon wafer. We investigated the use of a contact-mode atomic force microscope (AFM) in the generation of oxide patterns on silicon (100) surfaces. Subsequently, utilizing oxide patterns as Si etching masks, the Si substrate was dipped in aqueous KOH solution, where un-oxidized regions are selectively etched by aqueous KOH orientation-dependent etching (ODE). Using this simple process, 20nm convex NPAs with 100nm pitch can be fabricated successfully. Similarly, about 2nm concave NPAs with 100nm were obtained after the oxidized samples were dipped in acqueous HF solution, the oxide regions were selectively etched away. To demonstarte the capability of this technology, the ascii codes were written on silicon and the data storage density more than 10 times of current optical recording has been achieved. We also demonstrated that the minimum size of the pyramids and the minimum pitch could be easily controlled by the apex size of the pyramid, that is, the size of the oxidized region by AFM-based field-induced oxidation. The results indicated that this technique has potentials to provide a pathway to the higher densities that will be needed in the decades ahead.

Nanometer-scale oxidized patterns were fabricated on titanium (Ti) films deposited on silicon wafer using atomic force microscope (AFM) based field-induced oxidation process. Titanium surfaces can be oxidized at room temperature under ambient conditions with the tip of an atomic force microscope when applying a negative bias voltage between surface and tip. We investigated that the size of oxide patterns was dependant on tip-bias voltages, scanning speed, and relative humidity. We found that the attainable oxide features of titanium patterns were improved by increasing the scanning speed, tip-bias voltage and also by lowering the relative humudity. Fabrication of nanometer-scale structures on the Ti-metal film by AFM-based field-induced oxidation and subsequent chemical wet etching of the titanium in a dilute hydrofluoric aid (HF) was demonstrated. Patterns of Ti lines below 100nm in width successfully fabricated by the above-described method.

Sensors for the measurement of mechanical deformation are frequently used in industrial measurements. The sensors are realized using different technologies. The sensors of the type strain gauge is utilized for the measurement of change in length of geometrical dimensions. The strain gauge is realized on a thin cantilever structure. Piezoresistive strain gauge is realized by implanting resistive layers into substrate or with sputtered thin film resistance layer. Another type of the strain gauge is being developed for temperatures higher than 300°C. Simulation using CoventorWare program is used for verification of mechanical properties and temperature distribution in cantilever structures. At realized structures of cantilever with strain gauges, there have been measured basic parameters, as dependence of electric parameters of strain gauges on mechanical deformation, temperature dependence at different mechanical load, temperature stability of output parameters, temperature dependence of pn junctions in the structure. The piezoresistive coefficients, coefficients of deformation sensitivity, linearity, hysteresis, temperature coefficients of resistance, etc have been calculated from measured data. Wheatstone bridge with piezoresistors is used as transducer of mechanical deformation to electric parameters in the form of resistance change. The measured charateristics show very good linearity, small hysteresis and very good sensitivity.

This paper presents a three-dimensional microfabrication and integration technology for MEMS smart materials that utilizes a spray coating method. Spray coating is shown to be most effective for additional deposition on non-planar seurfaces. PZT films were formed both on flat and uneven surfaces at a thickness of about 1 μm. Perovskite structures were formed with suitable heat treatment and ferroelectric P-E hysteresis loop was also obtained. This paper is the first report from our group and other researches on the deposition of smart materials for MEMS using a spray coating method. Spray coating has been proposed as an effective three-dimensional coating method which can be used to deposit piezoelectrics, pyroelectrics, magnetics, etc. for sensors and actuators. The hydrophilic and hydrophobic properties between the substrate surface and ejected liquid are most essential process factors in the spray coating method for improving the film growth conditions.

A new type of oscillating transistor structure has been developed in thin film SOI applications.The oscillator's mechanical resonator has circular shape and vertical vibration. By using conventional SOI chips with other electronics it possible to add this resonator in same structure without complex process steps. The oscillating transistor can be used primarily in low frequencies (MHz). The component has one electrostatically driven electrode and two electrodes for drain and source parts. By using this component, the transistor can be driven electrostatically. It can have higher voltage current aplification -ratio than conventional transistor because of mechanic impact. For filter solutions coupling rods are not needed. The structure have been measured Q-value of 700 at 3,3MHz in normal room conditions

Micromachined glass capillary with a widely application in biological, pharmaceutical and chemical sample treatment and analysis. It also plays an important role in the microfluidic devices. A novel microfabrication method to form a glass capillary is presented here, in which glass channel wafer need to be anodicly bonded with a SiO2 surface of the silicon wafer and the silicon TMAH (Tetra-methyl-ammonium-hydroxide) wet ecthing process is followed. This method requests a lower bonding temperature comparing with conventional glass to glass fusion bonding approach and show an advantage.

A self-supporting 3D structure in SU-8 chemical amplified resist (CAR) using dual e-beam and ultraviolet (UV) exposure technique was fabricated. A single 15-micron thick layer of the negative tone SU-8 was firstly exposed with a mask using 365-nm UV to produce a latent image of the supporting structure. An additional structure was then exposed in its upper layer only with an electron beam. The dual exposed resist layer was then baked (PEB) and developed to give a 3D structure with self-supporting elements formed in the upper resist layer. This novel Dual Exposure Technique (DET) was based on the difference in the penetration depth in resist for UV photons and low-energy electrons. The 15-micron thick resist was spin-coated on Si wafer at a speed of 2000 rpm, soft-baled at 95°C for 5 min, and epxosed with UV dose of 500mJ/cm²> the resist was further irradiated with low-energy (5 keV) electrons with a relatively high dose of 5 μC/cm² to provide a reasonable acid concentration in the upper layer of about 0.5-micron thick. The resist was then postexposure baked at 95°C at an optimum time of at least 2 min, and developed for 3 min by immersion in a standard SU-8 developer. The cross-linking process in SU-8 was monitored using Fourier transform infrared (FTIR) spectroscopy to optimize the process conditions. The infrared absoprtion peak at 914 cm^-1 was found to be a useful indicator to study cross-linking in SU-8.

This paper presents an 8×8 optical switch consisting of a micro cantilever array. Each cantilever, with a vertical micro mirror located on one end of it, was driven by electrostatic actuation. The optical switch was fabricated using combined silicon process, electroplating and hot embossing. The optical switch, embossed with a polymer material, was aligned and assembled together with input and output optical fibers via grooves etched on a silicon substrate. Considering the fabrication process and material used, this optical switch is suitable for cost-effective mass production, and will potentially find wide applications for fiber-to-the-home communications.

By extending the bonding-tool life, the saving can be quite substantial. This paper demonstrates how the integration of new technological development in ceramic bonding tools to the base ceramic material with new treatment processes, extends the tool life by at least 2 times its current limit. No change in the dimensions, surface finish or appearance of the bonding tool as seen after it was processed, resulting in a more portable and repeatable process. Experimental results confirmed the potential capability of the treated capillary to go beyond the process capability presently in existence.

This paper discusses the effects of electro-deposition processing conditions on the film composition and surface morphology. The rate of Ag deposition onto the bump depends on various processing parameters like current density, agitation and temperature. Among these parameters, the Ag content in the bump was found to be most sesitive to current plating density. At various Ag content, the morphology of the deposited solder was found to be different. This is due to the different types of drain growth at different Ag content. A high content bump was found with a needle-like Ag₃Sn structure. This strcuture is believed to be the cause for the reduction in shear strength.