Flip-chip technology is becoming one of the most promising packaging techniques for high performance packages. Solder balls are used as the connection technique in the flip-chip method and the connections are reinforced by filling in the spacing between the chip and substrate with underfill. The function of the underfill is to reduce the stresses in the solder joints caused by a coefficient of thermal expansion (CTE) mismatch. The presence of polymeric underfill material will, however, make the flip-chip packaging system susceptible to interfacial failure. Thus, the purpose of this study is to examine the interfacial delamination between the dissimilar materials in order to increase the reliability of the flip-chip interconnection method, and to understand the effect of underfill curing conditions on the interface adhesion. In particular, we use a linear elastic fracture mechanics (LEFM) approach to assess interfacial toughness. For this purpose, four-point bending testing is performed to determine a critical strain energy release rate, Gc. In addition, nano-indentation testing equipped with atomic force microscope (AFM) is employed to determine structure and properties of the underfill layer.

In this study, Adhesion force and Nanotribological Characteristics of fluorocarbon (FC) films on Al deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) were evaluated. The contact angle of FC thin films on Al was measured to be around 110°. The surface energy was calculated to be 15 dynes/cm from the measurements of contact angles of polar and nonpolar solutions on surfaces. The contact angle hysteresis, which is an indicator for the surface heterogeneity, was lower than 30°. The friction force of FC films coated surfaces was three times lower than bare Al. The adhesion force of bare Al was measured to be around 9.6nN. The presence of FC films on Al reduced it to below 4nN. Fourier transform infra-red (FTIR) spectra showed the presence of fluorocarbon groups such as –CFn- and =CF=CF2.

Research conducted on steels is motivated by a technological need to further improve their properties. Among the different steel types, austenitic stainless steels possess good corrosion resistance and formability. However, they also have a low yield strength. One way of increasing the yield strength is by grain refining. This work presents a study on the cavitation erosion and friction behavior of AISI 304 austenitic stainless steel characterized by two different grain sizes: 2.5 μm and 40 μm. The cavitation erosion behavior in water with different pH values and at room temperature has been studied by using a 20 kHz ultrasonic vibratory apparatus. The grain size of the steels has an important effect on the nature of damage produced on the surface of the samples. The resistance to cavitation erosion increases with decreasing grain size. It was also found that cavitation erosion resistance of the two steels is sensitive to variations in the pH value; decrease of this value produces an increase in surface damage. Using a precision microtribometer, with applied loads in the μN regime, it was found that capillarity plays a dominant role. At the same loads, in high humidity environments, both the fine and coarse grain steels exhibit high friction relative to measurements performed under dry conditions. At high loads (20 mN and above) a reversal in microfrictional behavior occurs in that friction is higher under dry conditions than under moist conditions.

This paper presents the experimental results of impedance analysis and longitudinal vibration measurement of micro-fabricated 0.5 MHz silicon-based ultrasonic nozzles. Each nozzle is made of a piezoelectric drive section and a silicon-resonator consisting of multiple Fourier horns each with half wavelength design and twice amplitude magnification. The experimental results verified the simulation prediction of one pure longitudinal vibration mode at the resonant frequency in excellent agreement with the design value. Furthermore, at the resonant frequency, the measured longitudinal vibration amplitude gain at the nozzle tip increases as the number of Fourier horns (n) increases in good agreement with the theoretical value of 2n. Using this design, very high vibration amplitude at the nozzle tip can be achieved with no reduction in the tip cross sectional area. Therefore, the required electric drive power should be drastically reduced, decreasing the likelihood of transducer failure in ultrasonic atomization.

We propose a new concept of a gene field effect transistor (FET) for detection of allele specific oligonucleotide hybridization, which is in principle based on charge density change at the gate insulator. The electrical characteristics of the gene FET were found to shift after specific binding of biomolecules at the surface of the gate insulator. Allele specific oligonucleotide hybridization and reaction between double-stranded DNA and intercalator were successfully detected with gene FETs because they have intrinsic charges in an aqueous solution. Ability to discriminate single nucleotide polymorphism (SNP) was also examined using the gene FET. Our results show that control of hybridization temperature and utilization of intercalator lead to more precise SNP analysis using the gene FET.

Carbon nanotubes are excellent field emitters due to their high aspect ratios and small radii of curvature. These properties of the nanotubes offer tremendous possibilities for the realization of field emission devices. For the realization of the field emission devices controlled placement and alignment of the nanotubes over the substrate surface is desirable. Furthermore, field emission of the nanotubes in cylindrical geometry has added advantages over planar geometry. But, it is difficult to grow nanotubes uniformly over non-planar substrates such as long metallic cylinders by conventional CVD techniques. In the present investigation we have adopted a very simple technique called as Cold Plasma Chemical Vapor Deposition (CP-CVD) to grow carbon nanotubes over a catalyst-supported metallic wire by resistive heating in hydrocarbon atmosphere at about 750–C. The localized dissociation of the hydrocarbon gas over metallic wire allows well controlled growth of the nanotubes. The field emission performance of these nanotube coated wires was measured in a cylindrical geometry where the aluminum tube was used as an anode. Emission site density is found to be the most important parameter to control the field emission performance. Comparisons of the field emission properties were made using nanotubes grown in different hydrocarbon gases such as methane and acetylene. The effects of other parameters, such as growth time, was also investigated.

This study presents the results of polymerization of phenol to yield fluorescent polymer encapsulated within shells fabricated via layer-by-layer (L-b-L) assembly. Hollow polyelectrolyte microcapsules (shells) were prepared using weakly cross-linked melamine formaldehyde (MF) particles. Dissolution of the MF cores was achieved by changing the pH of the solution. Horseradish peroxidase (HRP), the catalyzing enzyme, was loaded in these capsules by taking advantage of the “open/close” mechanism of the capsules by altering the pH. The empty shells were then suspended in a concentrated solution of monomer. Since the monomer is a low molecular weight species, it freely permeates through the polyion wall into the shells. Addition of aliquots of hydrogen peroxide initiated the polymerization reaction and the polymer formed from the ensuing reaction was confined in the shells due to its high molecular weight. The model used for demonstrating this synthesis is polymerization of 4-(2-aminoethyl) phenol hydrochloride commonly known as tyramine hydrochloride to its corresponding polymeric form by reacting it with hydrogen peroxide. Fluorescence spectrometry (FS), confocal laser scanning microscopy (CLSM), and atomic force microscopy (AFM) were the characterization methods employed to confirm polymerization in situ shells.

This paper provides new investigation for the static and dynamic behavior of a MEMS parallel plate capacitor derived by analytical and numerical design modeling programs developed in Matlab. One significant finding is about the role, which has so far overlooked in many analyses, of a dielectric layer normally placed on top of the ground electrode to avoid short circuiting risks. It is demonstrated in this paper that this layer produces an increased force between electrodes that in turns decreases the well-known pull-in voltage, Vpi, as compared to the one calculated when this dielectric layer is not considered on the system's static analysis. Expressions for the static Vpi and its corresponding maximum stable electrode swing xpi are derived to take the above effect into account.

The system dynamic analysis is done with a user-friendly Simulink interface constructed to allow easy introduction of capacitor design dimensions, material parameter values and voltage signal stimuli. The impact of any combination of these parameters on the electro-mechanical system behavior, that is, the voltage-electrode position dependence data can be easily extracted and become of help for design decision making on the early design stages of this type of structures. This modeling tool interface is based on solving the full differential equation that describes the free electrode displacement without relying on linearizing the inverse quadratic electrode separation dependence of the electro-static force term. This approach intrinsically takes into account the voltage dependant k-spring softening effect derived precisely from a linearizing simplification. Finally, by applying a saw-tooth voltage waveform, the dynamic pull-in voltage and the maximum stable electrode travel range are observed to go well beyond the predicted static pull-in voltage and travel range values.

Thin-film silicon micromachined bridge actuators are fabricated at temperatures below 110°C on flexible polyethylene terephthalate plastic substrates. The micromechanical structures are electrostatically actuated both at the resonance frequency and at below-resonance frequencies, and the resulting deflection is optically monitored. Deflections up to 100 nm are measured below the resonance frequency with subnanometric precision. Resonance frequencies in the MHz range are observed in vacuum with quality factors of the order of 100. The movement is studied as a function of the geometrical dimensions of the actuators, of the actuation voltage and of the measurement pressure. The experimental data are analyzed using an electromechanical model. The performance of hydrogenated amorphous silicon based resonators on PET substrates is compared to that of similar microstructures on glass substrates.

A gas phase kinetic model of chlorine in an ICP reactor (Inductive Coupled Plasma) combined with a surface model have been developed to study the etching profile evolution of InP material. A gas phase chemistry model is used to predict the main neutral and charged specie fluxes impinging upon etched InP surface. These particle fluxes are then injected as input parameters into both a Monte-Carlo sheath model and a 2D surface model to predict the etch profile topography. The coupling between the gas kinetic model, sheath and surface models allows a direct prediction of the InP etch profile evolution versus reactor parameters (pressure, source power, Cl2 flow rate, DC bias on the substrate‥). A parametric study is carried out to show the role of some plasma parameters on etch rate, anisotropy and adsorbed InP surface state by chlorine.

This paper reports work concerning a silicon-based micro pump for use in a cryogenic cooling system. The diaphragm deflection, which is critical for the control of pumping capacity, was accurately derived using a combination of ZYGO and WYKO interferometer. The relationship between the pumping capacity and differential pressure was further achieved. Stress distribution was obtained using Micro Raman spectroscopy. It was found that Young's modulus derived from the maximum deflection increases with decreasing temperature. The compressive stress concentrates at the edge centers; whereas the tensile stress occurs at the diaphragm center. There is a fairly good match between the theoretical predications and experimental observations.

The formation of a Ba-Te surface on GaAs has been investigated. The surface was created using molecular beam epitaxy (MRS). A GaAs (100) surface was first exposed to Te and characterized using x-ray photoelectron spectroscopy (XPS), reflective high energy electron diffraction (RHEED) and low energy electron diffraction (LEED). The Te-reacted surface was then exposed to BaF2 flux producing a second reaction. In this reaction, the BaF2 dissociated leaving barium on the surface but no fluorine. This is in contrast to the clean (no tellurium) GaAs (100) surface in which BaF2 has been shown to grow single crystal. Although high order exists during early stages of the Ba-Te growth, further exposure gives way to a polycrystalline form. This paper discusses the formation and analysis of the Ba-Te surface.

Wetting of the pore walls of porous templates is a simple and convenient method to prepare nanoshell tubes. Wafer-scale fabrication of ferroelectric lead zirconate titanate and barium titanate nanoshell tubes was accomplished by wetting porous silicon templates with polymeric precursors. The ferro- and piezoelectric properties of an individual ferroelectric nanoshell tube either of PZT or of BaTiO3 were electrically characterized by measuring the local piezoelectric hysteresis. A sharp switching at the coercive voltage of about 2 V was shown from the hysteresis loop. The corresponding effective remnant piezoelectric coefficient is about 90 pm/V. We have also prepared highly ordered arrays of free-standing ferroelectric nanoshell tubes obtained by partial etching of the silicon template. Such materials might be used as building blocks of miniaturized devices and could have a significant impact in the field of nano-electromechanical systems.

This paper proposes how to determine a voltage sequence for time to realize a non-impact electrostatic micromanipulation by kinetic control of a detached particle. The system consists of a manipulation probe, a spherical microparticle, and a substrate plate. These objects are all conductive. The particle initially sticks to the probe tip due to adhesional force and is detached by the applied voltage. The force on the particle, which is generated by electrostatic interaction, is evaluated through a boundary element method. Although the numerical method is used, all the parameters are normalized. Based on the evaluation, we propose the simple method by accelerating and decelerating voltage, and clearly express the conditions of voltage and time by considering the total work to the particle during its flight. The discussion about the time reveals the feasibility of the method from the viewpoint of the through-rate of a power-source.

The sensitivity of Porous Silicon (PSi) to the presence of charged molecules and its large internal surface area represent two important properties that make this material and ideal candidate for electrical biosensor development. We have demonstrated the use of a macroporous silicon electrical sensor for label-free detection of DNA hybridization in real time as well as identification of organic solvents in liquid phase. Binding of DNA inside the PSi matrix induces a change in capacitance and conductance. Having demonstrated the suitability of macroporous silicon layers for real time detection of DNA hybridization on single devices, we have extended our findings to the fabrication of a microarray with individual device electrical addressing capabilities. On a crystalline p-type silicon wafer, process steps such as KOH etching and electrochemical dissolution are employed in selected regions to create a free-standing porous membrane for sensing applications. Individual electrical contacts are made on the front side of the wafer while the infiltration of the probe and target molecules is done from the back avoiding any direct interaction of the molecules with the contact sites. We will report on the design considerations of the electrical porous silicon array and the preliminary results obtained using synthetic DNA as a model molecule.

An actuator fabricated from the conductive polymer polypyrrole using microfabrication techniques is presented. This actuator utilizes the anisotropic volume change, which occurs under application of an electric field in polypyrrole grown in the presence of NaDBS. This volume change is in direction normal to the substrate, and is several times larger than lateral volume change utilized in polypyrrole microactuators to date. The actuator is applied in a microfluidic valve where membrane and microchannels are fabricated from a transparent elastomer using soft lithography. The use of elastomer enabled a good valve seal and encapsulation of the electrolyte used for polypyrrole actuation.

Carbon nanotubes have attracted significant attention in the scientific community due to their unique properties and potential applications. One of the most promising applications is a carbon-nanotube transistor. The motivation of this work is to find ways to connect carbon nanotubes directly to silicon using Ba as a chemical link. We studied chemical interactions between carbon nanotubes and BaF2 vapors using x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Surfaces of silicon wafers were chemically modified to allow the epitaxial growth of BaF2 using molecular beam epitaxy (MBE). Samples containing 2D single crystal islands of BaF2 were covered with carbon nanotubes with an average coverage of 10 nanotubes per um2. The samples were transferred to an outgasing station inside the MBE system and heated to 900°C for two hours in a pressure of 10-9 mbar. XPS C1s data before and after heat show a major change in the nature of the carbon nanotube electronic states. In addition XPS shows formation of a Ba-C “carbide like” bond and no presence of fluorine. AFM images of the same region taken before and after heat exposure show remarkable changes in the surface morphology of the carbon-nanotube wall.

This paper presents the results of a study to identify the effects of preheating for plasma oxidation (ashing) of patterned Polydimethylsiloxane (PDMS) for Bio-MEMS applications. PDMS creates an irreversible seal to itself as well as strong seals with glass, silicon, and silicon nitride. This process activates the surface by producing hydroxyl groups that last for several minutes to allow bonding. Several channels can be stacked to create 3D systems for microfluidic applications using PDMS alone or in combination with other materials to develop hybrid systems. For PDMS, bonding temperatures typically occur at room temperature. This research investigates the effect of preheating the materials prior to ashing. The investigators successfully demonstrate good bonding of PDMS to slides with a work adhesion on the order of 100 mJm-2. Preheating the samples at 65°C results in significant increase in work adhesion depending on mixture. The effects of processing temperature and chemical components on bond quality and work of adhesion are reported.

A nitrogen-free (N-free) dielectric anti-reflective coating (DARC®) was cost-effectively developed in a plasma-enhanced chemical vapor deposition (PECVD) reactor to eliminate the 193nm resist poisoning interaction caused when N2O is used as a precursor [1]. Although it was found that even a N-free ARC could poison sensitive 193nm resists with –OH radicals [2], which either exist inherently in the ARC or result from H2O absorption by the ARC surface, the current investigation has revealed that it was possible to minimize resist poisoning. Our investigation showed that compressive film stress directly correlates to H2O resistance. Therefore, it was possible to greatly improve the ARC resistance to H2O absorption by creating and maintaining a process regime that makes the ARC film dense. The dense ARC film demonstrated promising lithography performance with minimal resist poisoning as well as excellent shelf life and O2-ashing resistance. This paper explores the N-free DARC material, its development, lithographic integration results and implementation in a production environment to eliminate 193nm resist poisoning.

In this paper, a new revolutionary 3D manufacturing approach to rapid processing of 3D microstructures in both soft (SU-8) and rigid (Si) materials is introduced. This technique facilitates very fast prototyping without the need of masks, resulting in a low-cost, short-turnaround flexible fabrication process.