This paper presents dramatic improvements in the micro-fabrication of three-dimensional microfluidic channels and high-aspect ratio tunnels within the bulk of a fused silica substrate. We also report the fabrication of optical waveguides within the same substrate, which is a major step towards the integration of sensing capabilities within microfluidic networks.

This integrated device, which combines both fluidic channels and optical waveguides, opens new opportunities in bio- and chemical sensing. The flexibility of the improved manufacturing process offers substantial new design capabilities, especially for single channel probing and massively parallel processing and sensing.

Anodic bonding is a powerful technique used in MEMS manufacturing. This process is applied mainly for building three-dimensional structures for microfluidic applications or for wafer level packaging. Process conditions will be evaluated in present paper. An experimental solution for bonding three wafers in one single process step (“triple-stack bonding”) will be introduced.

Single crystal sapphire substrates were lithographically patterned with a system of parallel platinum electrodes, which were used to manipulate 1.58μm silica particles inplane, in the presence of an aqueous solution. Observation of the motion of these particles revealed the adhesion of some of them to the sapphire surface near the platinum working electrode, even in the range of pH where the zeta potentials of silica and sapphire are of the same sign. This phenomenon suggests the existence of localized differences in pH, attributable to the presence of potential determining ions produced in the faradaic processes occurring at the electrodes during the electrophoretic manipulation of silica particles. Atomic force microscopy (AFM) was used to corroborate this hypothesis, measuring the forces between a silica particle and a sapphire substrate in the presence of an applied field. The resultant force-distance curves demonstrate a change in the interaction forces between particle and substrate as a function of distance from the electrode. Variations in this interaction correspond to localized differences in the zeta potential of the substrate, which, in turn, are related to localized differences in pH. Quantification of these spatial variations in pH as a function of time yields further information about the diffusion of these faradaically produced potential determining ions across the substrate.

The term “microfabrication” has been used primarily as an acronym for silicon-based device fabrication. Recent developments in ceramic processing technology have resulted in cost-effective, scalable options of ceramic microfabrication that offer the potential for fabrication of devices with a number of advantages over silicon-based microdevices for specific applications. These advantages include the ability to fabricate devices with three-dimensional architecture, high-temperature operation up to 1200°C, porous layers for gas diffusion, and textured substrate properties for specific applications through wider materials selection. Processing routes for these ceramic microdevices with three-dimensional architecture include established processes such as tape casting, laser machining, lamination and sintering, or new processes such as reaction bonding and lost-mold techniques. The ability to fabricate three-dimensional feature geometries allows the application of these ceramic microfabrication techniques for device fabrication targeted at a number of applications such as point-of-use high purity gas generation, microchannel devices, microreactors, fiber-optic connectors and heat-pipes for microelectronics.

This work reports temperature dependent thermophysical properties characterization of electrodeposited Ni and NiMn alloys intended for LIGA Microsystems applications. A steady-state method is used to determine the in-plane thermal conductivity. Anisotropic thermal diffusivity characterization is performed using a photothermoelectric technique. The measured thermal properties are dependent on the deposition method and also on subsequent temperature annealing steps. The thermal transport measurement results are correlated with scanning electron microscopy studies of the grain structure and measurements of the electrical transport properties.

We describe a mass probing technique for characterizing the electro-mechanical behavior of micromembrane array actuators under electrostatic loads. The technique utilizes one or more arrays of center-positioned posts as a joint-link between an array of micro membrane actuators and a top movable rigid mass plate to generate 1D motion of the top mass owing to motion transfer from the deformed membranes. The micromembrane actuator arrays are fabricated using a stacked architecture similar to MUMPs in which the poly-Si structure material is replaced by metal-over-polymer composite, and final release is accomplished by a dry etch of a-Si sacrificial material. The mass probing technique is implemented by hybrid integrating a thick (100∼650-μm), heavy, and rigid mass plate (with a polished surface as a reflective mirror) onto the membrane array in which individual membrane actuators have a center interface post to act as mechanical linkage. A preliminary test of a 40-um pitch membrane array shows a 1st natural frequency of 2.1MHz of the membrane actuator. This was scaled down to ∼50KHz by a 2.7mmx2.7mm 200-μm thick mass load weighting 3.3-mg. Ignoring the small membrane mass, the lumped spring stiffness is estimated to be ∼70-μN/μm per actuator (3248 40-μm actuators embedded beneath the probing mass). Thus, motion transfer principle from micro size actuators to macro size components was demonstrated.

The commercial development of low-power electronics and electro-optics based on antimonides demands a better understanding of the mechanical properties of ternary and quaternary thin-film alloys fabricated from the InGaAlAsSbP material system. Of particular importance is the determination of Young's modulus of these materials. In this paper, a technique for studying the mechanical behavior of these thin films was developed by using microbeam bending and finite element modeling. The technique was successfully applied to investigate the mechanical properties of GaSb. A test structure consisting of an array of gallium antimonide microbeams was fabricated with lengths ranging from 50 to 500 μm long. The microbeams were deflected using a calibrated nanoprobe, thereby generating load-displacement curves. Young's modulus was then extracted from the data using beam bending theory and a finite element simulation of the structures under load. A total of five microbeams with the same trapezoidal cross-section and lengths of 80, 85, 200, 250 and 500 μm were tested to study the technique applicability and size scaling effects on the mechanical properties. It was observed that the 80 and 85 μm beams exhibited linear elastic behavior and the 200, 250, and 500 μm microbeams exhibited non-linear elastic behavior.

A method to fabricate nanometer scale SiC beams and nanoporous SiC shells using conventional microlithographic techniques combined with selective APCVD has been developed as an alternative to nanolithographic patterning and electrochemical etching. The process involves the selective deposition of poly-SiC films on patterned SiO2/polysilicon/SiO2 thin film multilayers on (100) Si substrates using a carbonization-based 3C-SiC growth process. This technique capitalizes on significant differences in the nucleation of SiC on SiO2 and polysilicon surfaces in order to form mechanically durable and chemically stable structures.

Many microelectronic chips contain embedded memory arrays. A single SRAM bit-cell contains several transistors. Failure of any of the transistors makes the entire bit-cell inoperable. Dual-beam Focused Ion Beam (FIB) combines the slicing capability of FIB with in-situ SEM imaging. The combination offers unparalleled precision in looking for root causes of failures in microelectronic devices. Once a failure site is located, an FIB lift-off method can be used to prepare a TEM sample containing the area of interest. Further structural, elemental information can then be acquired from the failure site. We report here analyses of single and multiple bit failures in SRAM arrays carried out using FIB/SEM, and in two cases TEM imaging and EDS/PEELS. Root causes of bit failures including remnant seed-layer metal between stacked vias have been identified.

The displacement loaded double cantilever beam (DCB), often referred to as the blade-insertion test or crack-opening method by the wafer bonding community, has become a common method for evaluating the work of adhesion of bonded wafer pairs. The test, while easy to perform, often yields results with large scatter and questionable accuracy. The mechanics of the specimen are investigated in detail in the current work. Expressions that demonstrate how wafer bow may lead to residual stresses that result in large errors in the calculated work of adhesion are developed. A three-dimensional finite element model is used to show that due to the circular wafer geometry and silicon anisotropy there is a large variation of the strain energy release rate across a straight crack front. The model is used to predict the actual crack front shape and shows good agreement with experiments. The results of the finite element simulations are compared to the traditional expression used for data reduction and implications of the model highlighted.

Microwave heating is an alternate means for material processing. The technique is promising for the accelerated synthesis of new materials. Microwave molecular sieves synthesis is combined with capillary confinement as a novel synthetic method. It is successfully demonstrated in the preparation of small ZSM-5 crystals by microwave hydrothermal synthesis within 1–1.7 μm channels of a capillary bundle. The geometric and spatial confinement offered by the capillary is expected to define and control the resulting crystal size distribution and orientation.

MCM-41, a mesoporous molecular sieve with a uni-dimensional regular array of hexagonal channels is investigated as a candidate for capillary confinement. The large porous channels of MCM-41(>35 å ) is attractive as a host for promoting inclusions of guest molecules or templates. The successful confinement of MCM-41 represents an important step towards the alignment of molecular sieves in a defined orientation within thin capillaries bundled (less than 5 μm channels). Ultimately, such an approach may be useful for the fabrication of new molecular sieve devices.

3D Small Angle X-ray scattering (3D – SAXS) was applied to study the microstructure and the deformation mechanism in PVDF – foils (polyvinyhdene fluoride). SAXS is a powerful tool to investigate structural changes in deformed polymers to reveal morphology at the nanometer scale. When PVDF is strained the structure changes from spherohtic isotropie to a highly anisotropie fiber bundle structure, which requires a full three-dimensional analysis of the SAXS signal.

We introduce a new method of producing polymer/nanotube composites where the morphology of nanotubes within the composite can be controlled. The thickness of the composite thin film can also be altered as required. Carbon nanotubes are grown from organo-metallic micro-patterns. The morphology of the tubes is determined by the conditions under which the tubes are grown and also, the type of catalyst used. These periodic nanotube arrays are then incorporated into a polymer matrix by spin-coating a curable polymer film on the as-grown tubes. The density and position of conduction channels through the thin film composite can be easily pre-determined by controlling the morphology of the embedded nanotubes. This technique of producing freestanding nanotube/polymer composite films represents a more efficient method of combining these materials for potential flexible electronic applications in an inexpensive and scalable manner.

The subject of this paper is to describe and comment on results from an etching model based on Monte Carlo method. It calculates the temporal profile evolution of the silicon substrate under an SF6/O2 plasma chemistry and a cryogenic process. This work was conducted in correlation with an experimental set-up to ensure the validity of the final results. Some in-situ measurements obtained in the gas phase allowed estimation of the incident kinetic parameters such as main ion and neutral fluxes. Collisionless sheath model is connected to the surface model to determine energetic and angular ion distribution functions. The study focuses on final properties of deep and thin trenches used in new power components. The development of a simulation tool appears as an useful mean to understand the role of certain parameters not easily controlled by the etching machine. In this article, results concerning the topography and defects usually met during such an etching process are shown and discussed.

Tensile, fracture and fatigue properties of single- and polycrystalline silicon and LIGA-Ni were evaluated by the resonance frequency and microtensile methods. A new method for evaluating the fracture toughness that combines these two methods was proposed. A pre-crack was generated in an electrostatically driven test specimen and a load was applied by piezoelectrically driven microtensile equipment. Before the microtensile test, a new surface micromachining technique including a two-step sacrificial layer removal was used. The pre-cracked specimen was attached to microtensile equipment by a UV-adhesive glass grip. The fatigue pre-crack was successfully introduced and the fracture toughness could be derived on the basis of fracture mechanics. The fracture toughness of the pre-cracked specimen was relatively low compared with that of the notched specimen, so that we were able to determine the effect of the notch tip radius. The fatigue properties of LIGA-Ni film were also evaluated. A tensile-tensile fatigue load was applied by a piezoelectric actuator, and real-time load-displacement curves were displayed via computer. The dependence of S-N curves, crack propagation rates and fatigue-notch factor on the applied load for 10 μm Ni film was analyzed.

This paper presents a scheme of micromanipulation with a liquid bridge and an analysis of the capillary forces involved. The following procedure is considered in this article: (a) PICK UP: a probe, with liquid in the tip, approaches the target object. (b) A liquid bridge forms between the object and the tip of the probe. (c) The object is picked up by means of the capillary force of the liquid bridge. (d) TRANSPORT: The probe ascends, moves to the target point, and descends towards a substrate. (e) PLACEMENT: At a given height, a second liquid bridge made from a drop previously applied at the target point on the substrate, forms between the object and the substrate. (f) The probe ascends and the probe-object bridge collapses.

The collapse can be predicted through the stability analysis of the bridge and its condition can be controlled by the regulation of the liquid volume. The liquid volumes required for the manipulation, in the first and second liquid bridge, are calculated in this paper.

To expand the utility of p+ mesoporous silicon devices in proteomic biosensor applications, we have conducted in-depth studies to quantify the impact of employing a strong base post etch process to modify the microstructure of microcavity sensors tuned to operate in the visible spectrum. Changes in the optical response and quality of the cavity are quantified as a function of potassium hydroxide (KOH) exposure and initial porosity. Our results show that an aqueous ethanol solution containing millimolar concentrations of KOH is an effective means not only to increase the porosity and pore size, thereby enhancing pore infiltration of large (40–50kDa) proteins, but also to fine tune the optical properties of a passive optical devices.

Electrical properties and thickness of insulating dielectric films directly affect electrical energy loss and electrical breakdown limit in electric micromachines. A thick, low-k film exhibits low parasitic capacitive effects that help with the reduction of electrical energy loss. The electrical performance can be deteriorated due to degradation of the electrical properties of the insulating dielectric material caused by process, device structure, and moisture. In this paper, we introduce the application of CYCLOTENE, a spin-on, low-k, BCB-based polymer in electric micromachines as insulating layer and interlevel dielectric. A novel approach using interdigitated capacitors for electrical characterization of CYCLOTENE and the effect of moisture absorption is introduced in this paper. The dielectric constant of CYCLOTENE is extracted from two steps of capacitance measurements, giving an average value of 2.49 with a standard deviation of 1.5 %. The dielectric constant increases by 1.2 % after a humidity stress of 85 %RH at 85 °C. The measured I-V characteristics of CYCLOTENE show a dependency of the breakdown strength and leakage current on the geometrical dimensions of the device under test. A breakdown strength of 225 V/μm for 2 μm finger spacing and 320 V/μm for 3 μm finger spacing, and a leakage current of a few to tens of pA are measured. The I-V characteristics degrades drastically after a humidity stress of 85 %RH at 85 °C, showing a breakdown strength of 100 V/μm for 2 μm finger spacing and 180 V/μm for 3 μm finger spacing. Based on the results of this study, it is expected that the electrical efficiency of an electric micromachine is improved using BCB-based polymers with negligible dependency on moisture absorption. On the other hand, the maximum performance that depends on the maximum operating voltage is adversely affected by the degradation of the breakdown voltage after moisture absorption.

How the surface morphology of a low index crystal surface evolves under annealing below the roughening temperature is still being investigated both theoretically and experimentally. This research is needed to understand the stability of nanostructures and for the control of step array on surfaces for various technological applications.

We have approached this problem from an experimental point of view by looking at the step morphology on the top of mesas patterned on Si(111) after flashing at 1200°C and annealing between 1000–1100°C. We find that after annealing, nanometer height ridges develop on the edges of the mesas except for one edge which becomes a source for steps advancing into the mesa top. The edge that does not develop a ridge is mainly determined by the initial miscut of the surface.

We attempt to explain our results through step dynamics and present some applications of this phenomena in creating novel arrays of steps.

In this paper, we report a new technology for fabricating interconnects and/or contact probes for LSI fabrication. We used a Mo-Cr spring wire as a lead wire. To reduce the resistance of the lead wire, we applied a Au plating bump to the tip of a Mo-Cr spring covered with Au thin film. Experimental results showed that contact resistance was lowered by forming an Au plating bump on the Mo-Cr spring wire, which was plated under controlled conditions.