A new technique to control etching rates of mask materials during XeF₂ etching was proposed. By exposing Si sample with SiO₂ and Si₃N₄ as mask materials to UV light of 3 W/cm² during XeF₂ etching, the etching rates of SiO₂ and Si₃N₄ were dramatically increased from 2.52 angstrom/pulse to 42.0 angstrom/pulse and from 27.3 angstrom/pulse to 403 angstrom/pulse, respectively. This new technique allows us to remove the mask material selectively and change the mask pattern by UV light exposure during in- situ etching process without additional photolithography step and opens a new silicon micromachining process for 3- dimensional fabrication. The multi-step Si structure was successfully realized by this technique.

In this paper, diamond microstructures were patterned over silicon/silicon dioxide substrate using the processes combined with bulk or surface micromachining, selective growth of diamond and plasma etching technique. Polycrystalline diamond films were prepared using microwave plasma enhanced chemical vapor deposition (MW-PECVD) and a gas mixture of hydrogen and methane. Two types of techniques for precise patterning of diamond microstructures were investigated in this paper. The first one was to selectively grow diamond films in the desired region by pre-depositing a Pt interlayer on silicon dioxide layer. The second one was to selectively etch the deposited diamond film in oxygen/argon plasma under an Al mask. Different microstructures, for example, microgear, microrotor, comb drive structure, etc. were successfully fabricated.

The MEMS-based Micrograting (MCG) is a basic building component in many optical systems. This paper presents the fabrication technique of a custom MCG whose optical surface can be reconfigured electrostatically. The ruling is made of SiO₂ and both the top and the bottom electrodes are made of Cr/Au. A robust three-mask process was designed and developed. The reduced ruling width (1 micrometers ) is not a simple miniaturization of previously reported 3 micrometers and 4 micrometers ruled microgratings. Because of mechanical integrity and fringe effects at the ruling edge during device operation, the design and fabrication of the new 1 micrometers ruled MCG require new material and process integration. To achieve self-alignment between the top electrode and the ruling, the top electrode is patterned first then the pattern is transferred to the ruling material by Reactive Ion Etch (RIE). Experiments show that the lift-off process results in a smoother top electrode than ion milling. Residual stress proves to be an important factor that influences the device performance. Because Ni is used as a hard mask for RIE, the resulting stress gradient causes the rulings to bend up. The actuation voltage is increased as a result of this increased air gap. Annealing experiments are performed to reduce the material residual stress and lower the pull-in voltage. Auger Electron Spectroscopy (AES) data shows that the adhesion layer (Cr) diffuses through the Au and gets oxidized when annealing temperature is higher than 450 degree(s)C. It was found that the optimum annealing condition is at 350 degree(s)C for 1 hour. Finally, optical tests these prototypes show that the diffraction patterns switch at about 11 V, much lower than the devices reported previously.

The issues regarding structure design and fabrication in improving the performance of MVGs are discussed. Although using (111) Si wafer with existing HARM process is appropriate, some limitations on design and fabrication still exist. This study proposes a novel BELST process that can improve the device performance as well as fabrication capability of the existing techniques. The salient features of the process are described, and various design concepts have been demonstrated from the fabrication results. According to the result, MVGs with desired shape and thickness can easily be obtained using the developed BELST process.

The ability of various deposition processes and materials to fill and planarize topographical features (trenches deeper than 10 micrometers ) is investigated in this work. Three different deposition processes are considered: LPCVD (Ge), PECVD (Ge, Si₃N₄, SiO₂) and spin coating (BCB, resist, polyimide). Comparing LPCVD and PECVD processes show that, for the same trench width, thick PECVD layers can close off trenches from the top, while thick LPCVD layers fill the trenches completely. The use of PECVD layers is thus advantageous for sealing applications, where a low bottom step coverage is desired. LPCVD layers on the other hand are very useful for planarization purposes where a low ratio between the deposited film thickness and the planarized trench width is desired. Also the deposition of polymers by spin coating yields excellent planarization results with a simpler process and lower thermal budget compared to LPCVD processes. All polymers investigated fill the trenches totally. If these planarization layers are used as sacrificial layers, they should be etched isotropically and selectively with respect to the structural layer. Ge can be etched in oxidizing solutions (H₂O₂/H₂O) and the sacrificial etch of Ge is selective towards Si, SiO₂ and many other layers. SiO₂ can be removed by wet or vapor HF, and resist, polyimide and BCB can be removed by O₂ or O₂/SF₆ plasma. Which layer should be used depends on the trench fill requirements, the thermal budget and the further processing needed.

For patterning thick photoresist films, x-ray lithography is superior to optical lithography because of the use of a shorter wavelength and a very large depth of focus. SU-8 negative resist is well suited to pattern tall, high-aspect ratio microstructures in UV optical and x-ray lithography with rapid prototyping capability due to its high sensitivity. The negative tone of the SU-8 resist offers advantages in fabricating multi-level and non-planar microstructures using x-ray lithography or a combination of x-ray and UV optical lithography. In this paper, we present a fabrication process for multi-level metallic mold insert by a combination of multi-layer SU-8 patterning, poly-dimethylsiloxane (PDMS) molding, and nickel electroplating to make final nickel mold inserts that are suitable for injection molding and hot embossing of plastics and ceramics.

For the past five years, we have been investigating and advancing processing capabilities for deep x-ray lithography (DXRL) using synchrotron radiation from a bending magnet at the Advanced Photon Source (APS), with an emphasis on ultra-deep structures (1mm to 1cm thick). The use of higher-energy x-rays has presented many challenges in developing optimal lithographic techniques for high-aspect ratio structures: mask requirements, resist preparation, exposure, development, and post-processing. Many problems are more severe for high-energy exposure of thicker films than for sub-millimeter structures and affect resolution, processing time, adhesion, damage, and residue. A number of strategies have been created to overcome the challenges and limitations of ultra-deep x-ray lithography (UDXRL), that have resulted in the current choices for mask, substrate, and process flow at the APS. We describe our current process strategies for UDXRL, how they address the challenges presented, and their current limitations. We note especially the importance of the process parameters for use of the positive tone resist PMMA for UDXRL, and compare to the use of negative tone resists such as SU-8 regarding throughput, resolution, adhesion, damage, and post-processing.

The Center for Advanced Microstructures and Devices (CAMD) at Louisiana State University (LSU) supports one of the strongest programs in synchrotron radiation based microfabrication in particular, in deep X-ray lithography (DXRL) in the USA. For taller microstructures above 500 micrometers height, a harder source has been made available at CAMD using a 5-pole 7T super-conducting wiggler that has been installed in one of the straight sections of the synchrotron ring. A beamline and exposure station designed for ultra deep X-ray lithography (UDXRL) has been constructed and connected to the wiggler. An in-air scanner system has been built and installed at the beamline in approximately 10m distance to the source point. The scanner system features a fully water-cooled mask and substrate assembly to allow accurate patterning of high aspect ratio microstructures. The performance of the entire exposure system has been qualified and being proved compatible to standard exposure tools. Simultaneous exposure of a stack of four graphite substrates with 500 micrometers thick PMMA resist layers illustrate the potential for a cost-effective mass production of LIGA microstructures at hard UDXLR sources. The samples have been exposed using a 600 micrometers thick beryllium mask with 50 micrometers gold absorber. Dose calculations for the stacked exposures and preliminary exposure results as well as measurements of patterning accuracy over structure height and structure quality are presented.

In today's MEMS fabrication, stiction remains one of the fundamental manufacturability challenges. A major step towards eliminating stiction problems is the use of a gas-phase process for the beam release. To date, an anhydrous HF/water vapor MEMS release process has been in production for two years with excellent repeatability and reliability. This stiction-free anhydrous HF/water vapor MEMS release process for accelerometers has been further characterized to determine and solve manufacturing challenges associated with the differences between aqueous-based and vapor-phase release processes. Detailed process characterization to further understand material compatibility with the HF/water vapor release process has been investigated. Various films such as oxides and nitrides of silicon, photoresist, and metals such as gold and aluminum have been characterized for their compatibility with the anhydrous HF/water vapor MEMS release process. Initial results with wafer dicing films are promising as these films show little degradation during extended vapor-phase release processes. The resistance of the wafer dicing films to the anhydrous HF/water vapor process makes it possible to complete the sacrificial oxide release process after substrates have been diced.

Laser induced micro chemical etching of silicon can be used to quickly and cheaply machine high-quality three-dimensional structures that would otherwise be nearly impossible to fabricate, in particular THz waveguide structures and quasi-optical components. At the University of Arizona, the construction and characterization of the first laser micro-machining system designed for waveguide components fabrication has been completed. Our system can be used to fabricate focal plane heterodyne mixer arrays, coherent beam combiners, AR grooved silicon lenses, phase gratings, single mode filters and more. Laser micro machining enables the fabrication of three-dimensional structures down to a few microns accuracy and up to 6 inches across in a short time. This presentation discusses the design and performance of our micro-machining system, and illustrates the type, range and performance of quasi- optical components this exciting new technology will make accessible.

A study of the laser annealing effect for the thermal evaporated Al thin film onto micromirrors of optical switch and (100) Si subtrates is reported. The 2 X 2 optical switches has been fabricated through DRIE process. The input laser energy has been changed from 150 mJ/pulse to 350 mJ/pulse and the number of pulse also changed. The surface morphology is investigated by SEM micrograph and the roughness is examined by AFM. The reflectivities of the samples are measured by IR reflectometer and the results are normalized with gold. In case of the energy above 200 mJ/pulse, the reflectivities are improved up to above 0.98 from the incident beam region of 1300 nm to 1550 nm. The improvement of reflectivity is caused by the reflow process induced laser annealing. By the reflow process the grain have been growth and agglomerated for the surface planarization. The energy for planarization is sufficient as 1 pulse incident laser beam. According to the number of pulses, reflectivity is somewhat degraded by excess heat of reflow in case of above 5 pulses. There is minor morphology change with input laser energy.

An investigation of the micromachining of trenches in lithium niobate (LiNbO₃) using direct imaged 248 nm KrF (krypton fluoride) excimer laser photoablation is presented. High resolution trenches, 2-20 micrometers wide and 0.5-7.5 micrometers depth have been produced. These trenches are assessed and are deemed suitable for the machining of integrated optic structures with particular application in the enhancement of electrodes for broadband optical intensity modulators.

Novel methods using pulsed laser ablation have been developed for the manufacture of micro-devices with axial symmetry in ceramic materials. Such techniques allow the prototyping and production of micro-parts that are very difficult or even impossible to process by other mechanical and/or chemical methods. To demonstrate these techniques we have manufactured small conical counter-electrodes for use in a Scanning Atom Probe (SAP) instrument. This paper details all the innovative steps developed to produce the double cone shaped electrode and demonstrates the potential for mass production of other devices of similar shapes and dimensions. Many different laser processing strategies for fabricating the cones have been tried in order to achieve a result with satisfactory accuracy and quality. High quality devices have finally been produced in quantity using a combination of excimer laser mask projection and UV Yag laser cutting. The laser methods developed allow micro-parts of an overall size down to 0.1mm and tolerances of a few microns to be manufactured directly in ceramics, glasses, or crystalline materials.

We present a mathematical model of particulate formation and dynamics in the laser ablation plume. This model is presented in a practical layout and applied to an example problem predicting the behavior of silicon, a material commonly used in the fabrication of microdevices. Additionally, we examine an intermediate intensity regime of laser ablation, in which there are multiple cooling mechanisms that can be considered important, but plume ionization is not significant. Results are discussed with an emphasis on pulsed laser ablation manufacturing processes, which often take place at atmospheric pressure. Important observations derived from this work are as follows: (1) The plume is quickly condensed and stopped in less than a microsecond in a distance of less than a millimeter at atmospheric pressure. (2) Particulates predicted by this model are on the order of 10 angstrom in diameter, the majority of which condense back onto the target surface.

Nowadays the application of specially designed grippers in micro technology is an important topic and a necessity for the industrialisation. In order to transfer the manual assembly of micro electro mechanical system (MEMS) to an automatic assembly process, specially designed handling tools with sensing capabilities are required. Keeping the dimensions of the microparts in mind the handling and assembly process requires supervision with microscopes, positioning with high precision and application of specially designed tools. This paper describes a miniaturised mechanical gripper system with specially designed grippers and with implemented force-feedback for general microassembly purpose. The described grippers are fabricated from spring steel by wire electro-discharge-machining (EDM). The design of the microgripping system allows handling of pieces with sizes from 10 micrometers up to 2 mm.

Microassembly deals with micron or millimeter scale objects where the tolerance requirements are in the micron range. Typical applications include electronics components (silicon fabricated circuits), optoelectronics components (photo detectors, emitters, amplifiers, optical fibers, microlenses, etc.), and MEMS (Micro-Electro-Mechanical-System) dies. The assembly processes generally require not only high precision but also high throughput at low manufacturing cost. While conventional macroscale assembly methods have been utilized in scaled down versions for microassembly applications, they exhibit limitations on throughput and cost due to the inherently serialized process. Since the assembly process depends heavily on the manipulation performance, an efficient manipulation method for small parts will have a significant impact on the manufacturing of miniaturized products. The objective of this study on 'parallel micromanipulation' is to achieve these three requirements through the handling of multiple small parts simultaneously (in parallel) with high precision (micromanipulation). As a step toward this objective, a new manipulation method is introduced. The method uses a distributed actuation array for gripper free and parallel manipulation, and a centralized, shared actuator for simplified controls. The method has been implemented on a testbed 'Piezo Active Surface (PAS)' in which an actively generated friction force field is the driving force for part manipulation. Basic motion primitives, such as translation and rotation of objects, are made possible with the proposed method. This study discusses the design of the proposed manipulation method PAS, and the corresponding manipulation mechanism. The PAS consists of two piezoelectric actuators for X and Y motion, two linear motion guides, two sets of nozzle arrays, and solenoid valves to switch the pneumatic suction force on and off in individual nozzles. One array of nozzles is fixed relative to the surface on which the objects are placed, while the other set is actuated by the actuator relative to this surface. The combination of piezoactuation and pneumatic force generates a friction force that can manipulate multiple objects simultaneously, without grippers. We model the manipulation as the quasistatic motion with an approximation of limit surface. Also an experiment was carried to validate the proposed idea and the design of the prototype. The object manipulated in the experiments was a small piece of silicon wafer (1 mm X 4 mm) with 10 Hz of 10 micrometers stroke of the piezoelectric actuation system. The method is being extended to the parallel manipulation of small objects such as v-groove fiber assemblies and MEMS dies. The combined precision of piezoelectric actuation and speed of parallel manipulation is expected to yield a low cost microassembly method.

A crack-opening method used for characterization of silicon direct wafer bonding (DWB) techniques was analyzed. Mathematical model describing the influence of the pattern shape on the wafer pair resistance curve, so-called the R-curve, was developed. Two-dimensional patterns were created on a mirror-polished silicon wafer surface by a combination of photolithography, deposition and etching steps. Experimental observations did show that structured wafers can be used for large bond energy measurements. We propose utilization of structured wafers for bond energy measurements. It allows R-curve shape manipulation, increases the method sensitivity, and reduces probability of wafer failure. The resulting theory can also be used for developing new experimental methods for large bond energy measurements.

In this report, a new way of wafer dicing is carried out by laser induced thermal shock process. This system consists of the use of a Nd:YAG laser to heat up the wafer surface following by a cooling fluid along the scanned line. The temperature gradient created by the laser heating and the gas cooling will cause a micro-crack on the wafer surface along the scanned line and the resulting crack propagation finally separate the silicon wafer into two pieces. As there is no material loss and removal during the separation process, the wafer dicing line width can be as small as sub-micron. The cross section of the wafer is smooth comparing with other separation methods and a high separation speed of 70 mm/s is achieved.

The packaging of microelectromechanical devices is currently one of the most challenging in this emerging field. The available packaging technologies often provide large dimensions and expensive solutions, thereby limiting the market penetration of micro electromechanical devices. A wafer level chip scale package (WLCSP) with an integrated cavity above the active area of the device for microelectromechanical components is described. This WLCSP is designed for devices with mechanically moving components such as micromirrors, miniature gyroscopes, acceleration detectors, etc.

This paper introduces a new microfabrication technique that combines ultraprecision micro machining (milling, turning, drilling, and grinding) with sacrificial/structural multi-layer manufacturing processes to produce assembled, three-dimensional microsystems. These systems can comprise true 3-dimensional features that span in size from micrometers through millimeters and can be manufactured from a variety of metallic and polymer materials.

Silicon grisms are very attractive as devices for IR spectroscopy in terms of high resolving power and compactness, necessary for many astronomical applications and for implementation of spectroscopic modes in large telescopes respectively. We present the fabrication process of a silicon grism as composed by an IR transmission grating coupled to a silicon prism. The silicon gratings were manufactured using silicon micromachining techniques, as electron beam lithography and wet anisotropic etching, achieving good uniformity over all the large surface (32 X 32 mm²) and grating facets of excellent optical quality; the final grism was realized by means of direct bonding of the grating onto the prism face. The results of laboratory tests on the first prototype are presented.

Thick-gold-multilevel damascene-interconnect technology makes it possible to fabricate >10-micrometers -feature ultrahigh-speed devices on Si. Adding H₂O₂ to a conventional KIO₃-based slurry triples the removal rate of gold in chemical mechanical polishing (CMP). A ratio of H₂O₂ to slurry of approximately 1:1 is found to be the optimum for obtaining the highest gold removal rate. X-ray photoelectron spectroscopy (XPS) analyses show that gold is oxidized in spite of its chemical stability when the removal rate is high. The gold is oxidized due to the reduction of iodine at the optimum H₂O₂ mixture ratio. This CMP of gold enabled us to make a thick (>10 micrometers ) gold-multilevel damascene-interconnection structure for the first time. Integration of full-wafer wafer-bonded uni-traveling carrier photodiodes (UTC-PDs) with the gold multilevel interconnections as coplanar waveguides (CPWs) on a Si wafer has been achieved using this gold-CMP process.

New lithographic, deposition, and etching tools for micro fabrication on planar silicon substrates have led to remarkable advances in miniaturization of silicon devices. However silicon is often not the substrate material of choice for applications in which there are requirements for electrically or thermally insulating substrates, low capacitance, resistance to corrosion, or hermetic sealing. Some of the MEMS packaging materials such as ceramics, polymers, and glass are currently being used to fabricate many microdevices. To support the rapid advancements of non-silicon MEMS it is necessary to introduce innovative techniques to process these MEMS packaging materials. In this study we present the application of pulsed laser ablation of ceramics, polymers and glass (MEMS packaging materials) to assist in fabrication of MEMS devices. Microstructuring of Al₂O₃ ceramic, polymers Poly-Vinyl-Alcohol (PVA), polystyrene (PS), and Pyrex glass were performed and studied by pulsed lasers at 193-nm, 266-nm and 308-nm wavelengths.

Micromachined cantilever structures are commonly used for measuring mechanical properties of thin film materials in MEMS. The application of conventional cantilever theory in experiment raises severe problem. The deformation of the supporting post and flange is produced by the applied electrostatic force and lead to more reduced measurement value than real Youngí»s modulus of thin film materials. In order to determine Youngí»s modulus of aluminum thin film robustly and reproducibly, the modified cantilever structure is proposed. Two measurement methods, which are cantilever tip deflection measurement and resonant frequency measurement, are used for confirming the reliability of the proposed cantilever structure as well. Measured results indicate that the proposed measurement scheme provides useful and credible Youngí»s modulus value for thin film materials with sub-micron thickness. The proved validation of the proposed scheme makes sure that in addition to Youngí»s modulus of aluminum thin film, that of other thin film materials which are aluminum alloy, metal, and so forth, can be extracted easily and clearly.

In this study a stochastic model is applied in order to determine flow characteristics at the particulate level in a micro-channel. Model equations were discretized using Central Difference and Backward Difference methods and solved using the Jacobi method. The solution to the model equations provides the probability distribution of the distance traveled by a particle in the micro-channel as a function of time and reflects the dispersion property of the flow. From the probability distribution, residence time of a particle in the micro-channel is determined. Knowledge of Residence time and of dispersion characteristics is essential in studying the performance of a micro-reactor or in studies related to molecular or particulate flow in biological systems.

We report the fabrication process of a silicon target with a rectangular slit as an instrument for measuring the size and the angular divergence of high charge-density electron beams in particles accelerators. Bulk micromachining of silicon wafers by means of anisotropic etching allowed the definition of slits with parallel straight edges and low disuniformity. The disuniformities of the completed device evaluated by scanning electron microscopy were found to be tolerable with respect to the wavelength used in the experiments. Tests of the fabricated targets are in progress in the injector of ELETTRA, the synchrotron radiation facility in Trieste, Italy.

The comb actuator deformed by microloading effect in DRIE process generally has í«Lí» shape comb electrodes. Therefore, the actuator shows nonlinear differential driving characteristics. A simple modeling is suggested and simulated to explain the driving characteristics. For modeling convenience, the damaged comb electrode is assumed to be a simple í«Lí» shape. According to the modeling, the resonant frequency is estimated to increase as the bias voltage increases. The static displacement curve shows í«Sí» shape.

It has been conjectured that the primary cause of roughness of silicon surfaces etched in KOH is random masking of the silicon surface by the H₂ bubbles produced in the reaction. In order to test this model, we have observed and measured bubbles occurring during (100) silicon etching in aqueous KOH solutions. We have confirmed the trends for the average bubble departure radius R_d and average dwell time T_d noted by previous authors under different circumstances: T_d invariably decreases for increasing temperature and concentration and R_d decreases with increasing concentration and flow speed. Two distinct kinds of topography result from the hour long etch. A region that was covered by bubbles looks like a superposition of shallow depressions, with lateral radii comparable to the bubble departure radius and roughness consistent with a pseudo-masking model . Therefore the roughness is dominated by the effect of bubbles and determined by bubble parameters if when and where those do occur. A different roughening regime, resulting in hillocks, is reached by decreasing T_d and bubble density (for instance by increasing flow speed). Depending on the parameters bubbles do not occur over all the surface being etched, or do not occur at all.

In this paper, we report on mechanical and structural properties of in-situ n- and p-type PECVD Silicon Carbide (SiC) thin films for post-process surface micromachining. The effect of the doping on the film properties is investigated and compared to undoped layers. A clear increase in deposition rate is observed when adding the doping gas. The effect is more pronounced for p-type doping. The etch rate in a reactive ion etcher using fluorine-based chemistry is clearly affected by the doping gas level. For p-type films a slight decrease is observed, while for n-type films a sensible increase is measured. The stress is in the tensile region and somewhat larger than for undoped films. However, while for the phosphorous-doped films this increase is very small and almost insensitive to the doping gas level, for the boron-doped films the effect of doping level is much more pronounced. Structural and compositional analysis is preformed to understand the effect of the doping on the mechanical properties of these films.

Polymer-based microfluidic platforms have great potential for use in BioMEMS applications because many polymers are low cost, biocompatible, and have good processibility. However, packaging (i.e., sealing the platform with a lid) is a challenging issue in their fabrication. In this paper, we compare several available bonding techniques such as adhesive tape bonding and chemical-assisted bonding with a new method recently developed in our lab: resin-gas injection-assisted bonding. This new approach can easily seal microfluidic devices with micron and sub-micron sized channels without blocking the flow path. It can also be used to modify the channel shape, size, and surface characteristics (e.g., hydrophilicity, degree of protein adsorption). By applying the masking technique, local modification of the channel surface can be achieved through cascade resin-gas injection. Experiments are carried out to demonstrate the bonding efficiency and surface modification.

In very large scale of integration (VLSI) processing photolithographic techniques control the patterning of thin film and the deposition of dopant used to make transistor gates and metal contacts. Microelectromechanical systems (MEMS) processing uses the same techniques to create structural components that are essentially submillimeter-sized machines parts. These parts usually require post-fabrication processing or assembly in order to become finished devices. MEMS technology can generally be categorized into two groups as bulk and surface micromachining. These categories respect not only different fabrication processes but different post fabrication techniques for finishing the mechanical subsystem.

Ultrananocrystalline diamond (UNCD) with grain sizes in the range of 2 - 5 nm is produced using a microwave plasma chemical vapor deposition process with argon-rich C₆₀ or CH₄ plasmas. This material has excellent mechanical properties: high hardness and Young modulus, and an extremely low friction coefficient (approximately 0.01). It is resistant to chemical attack, and is potentially biocompatible. These properties make UNCD a very good candidate for a diamond-based microelectromechanical systems (MEMS) technology. We report on the micromachinability of this material by selective seeding, selective growth and reactive ion etching, in conjunction with SiO₂ sacrificial layers for fabricating 3-D structures with freestanding or movable parts. These micromachining techniques are used to develop a totally UNCD-made turbine as a demonstration for UNCD-based MEMS.

SEMICONDUCTOR300 was the first pilot-production facility for 300mm wafers in the world. The company, a joint venture between Motorola, Inc. and Infineon Technologies started in early 1998 to test and compare process, metrology and probe equipment, develop robust processes, and manufacture products using a 300mm wafer tool set. The lithography tools included I-line steppers, an I-line scanner, a DUV stepper, and DUV scanners. All of these exposure tools were running in-line with various photoresist coat and develop tracks. The lithography tools were used to build both 64M and 256M DRAM devices and aggressive test vehicles. The process capability of the initial 0.25 micrometers reference process was done and compared to the 200mm data set of the sister factory. Automation issues for lithography tools were addressed and the cost metrics were calculated. SC300 demonstrated that a manufacturable 300mm lithography tool set and process for various ground rule devices was possible with the required performance in image transfer, CD control, and overlay. Further testing on 0.18micrometers and 0.15micrometers ground rule features indicated a sufficient process window for potential manufacturing. Additionally, it was demonstrated that non-concentric subfield stepping was feasible.

Direct spray coating, a new photoresist deposition technique, is investigated to evaluate its potential for pattern transfer on wafers with very large topography. An Electronic Vision EV101 spray coating system is employed and AZ4823 photoresist is selected to form a thick layer of resist on flat wafers and to produce sufficient coverage on wafers with deep cavities. The dependence of the resist thickness on the dispensed volume of the resist is studied. A few key parameters are optimized to achieve a uniform resist layer. Special attention is paid to the layer characteristics when sprayed on wafers with cavities of various depths. A few applications of spray coating are shown to further illustrate its possibilities in MEMS.

This paper presents notable improvements in the ability to control and distinguish the composite stress components within plasma enhanced chemical vapour deposition (PECVD) silicon nitride. Wafer curvature measurements complemented by stress structure fabrication and characterisation has enabled detailed analysis of in- and out-of-plane stress. Analytical modelling has allowed clarification of the relative contribution to the wafer curvature attributed solely to the stress gradient, which is of the order of 10^-5 microns. Therefore the measured wafer curvature (due to composite stress), can be thought as a true representation of the actual wafer curvature due solely to the in-plane stress of the deposited thin film. This work represents a considerable advance compared with our previously published stress characterisation work on PECVD silicon nitride, which relied solely on wafer curvature measurements. However, the fabricated ring-beam and fixed-fixed structures were unable to resolve the in-plane stress component in high out-of-plane stress regimes. As predicted, at the zero stress gradient point, the fixed-fixed structures did measure an in-plane longitudinal compressive stress of -50MPa, which agrees well with wafer curvature measurements. Both stress components may now be repeatably controlled to realise tensile or compressive stresses (in-plane longitudinal) and positive or negative stress gradients (out-of-plane), by varying the RF deposition power. This new methodology allows for optimisation of the material for specific applications and in addition enhances the accuracy of micromechanical device models.

The step coverage of dielectrics is important for the microelectronics industry and critical to Micro-machined products and High Voltage MEMS drivers. The techniques used to fabricate MEMS structures require void free refill processes and even film deposition along deep trenches to protect against etch chemistries. High voltage drivers used to actuate MEMS devices benefit from dielectric isolation, which reduces the need for large tub formation between devices. It also enables 'system on chip' solutions for MEMs devices and protection against voltage spikes. This paper presents a process developed at Analog Devices Belfast that enables an LPCVD TEOS furnace to perform a highly conformal trench refill without equipment modification. The conformality is over 95% for 20 micrometer deep trenches and maintains a conformality greater than 85% in 50 micrometer deep trenches. This compares with 75% conformality which is considered excellent for 20 micrometer trench refills obtained using previous LPCVD TEOS processing. The process is shown to have benefits in conformality, breakdown voltage, and stress over standard trench fill processes including Ozone TEOS. The densification of the TEOS film has been optimized for electrical parameters using CV and IV techniques, while XPS, FTIR and spectroscopic ellipsometry are used for physical characterization. Stress is a very important parameter for micro-machining and the conformal TEOS has a film stress which is tensile 30 - 40 MPa as deposited and compressive 100 MPa after densification. The breakdown voltage has been measured at 8.5 MV/cm compared to 7.5 - 9 MV/cm for a typical densified TEOS film and the refractive index is 1.456 compared to 1.465 for a thermal oxide. Analog Devices Belfast is part of the Micro-machined Products division and provides SOI and customized SOI for the MEMs and IC market.

Titanium-nickel (TiNi) based shape memory alloys (SMAs) are used in a wide range of applications. They are especially practical as thin film actuators because of the large work output per unit of actuator mass and ability for rapid thermal cycling due to large surface to volume ratio. Sputter deposited thin TiNi film has been developed for use in miniature actuators for microvalves, microrelays, optical switches and also for building small implantable medical devices. Chemical composition of the deposited SMA must be held within close limits and for the film to have shape memory properties a crystallization anneal is required. To avoid flaws in film quality the surface on which SMA is deposited has to meet certain criteria. Basic MEMS processes (photolithography and chemical etching) are used for device fabrication. Although TiNi is resistant to most chemicals, some acids used in MEMS can damage it. Thus, selection of processes and reagents compatible with TiNi requires care and experimentation. This paper discusses some applications of SMA thin films along with experience gained in bringing device s to production readiness. It illustrates simple design rules for incorporating shape memory microactuators in MEMS devices and describes some of the pitfalls to be avoided.

Two dimensional micromirror array(MMA) is designed and fabricated to be used as a spatial light modulator for biochip fabrication. The optical projection system is setup using the MMA for maskless photolithography process, which is applied to photochemical surface modification. The photoresist (AZ1512) pattern is fabricated by the MMA projection in the maskless photolithography system, which consists of MMA and other optical components like projection lens. The patterned PR on a chip substrate is analyzed to improve pattern edge definition. The parameters of the optical system, which are lens location, incident angle of the UV light and the MMA location, are adjusted to obtain fine pattern edge definition by the MMA deflection. To immobilize proteins on the specific surface regions of a chip substrate to make protein patterning, nitroveratryloxycarbonyl(NVOC) group is used as a photolabile protecting group. The surface which is protected by NVOC group, is selectively irradiated by UV illuminator using the MMA. After removing the NVOC group, FITC(fluorescein isothianade) is tagged to the NVOC-cleaved site to find out the photo-cleavage condition of NOVC group by UV irradiation in the maskless photolithography system. Using the photocleavage condition, biotin was coupled to the NVOC-cleaved site. Then, we could obtain streptavidin-patterned surface.

Micro-scale biochemical reactors have been developed from a polydimethylsiloxane/enzyme (PDMS-E)biopolymer. Micro-reactor channels 125 micrometers in depth, 500 micrometers wide by 50 centimeters long contain fixed triangular features for enhanced fluid mixing. All channel features are composed of the same PDMS-E material. Conversions of urea by urease enzyme of up to 70% have been obtained at an overall flowrate of 0.4 mL/min. Additional PDMS-E biopolymer systems containing amyloglucosidase (for converting starch to glucose) have demonstrated enzymatic activity.

A modulated continues wave argon ion laser has been used to get lamb waves in silicon membrane. In this report, the basic principle of conversation from optics to thermal then acoustic waves was deduced. The experimental set-up, the analysis of the results and the possible way to obtain a given mode of lamb wave were described.

This paper describes the fundamentals of diffractive optics diffuser design, with an emphasis on common pitfalls and important design decisions. In addition, several new design and fabrication methods are presented, which overcome many of the current limitations of multi-level diffractive diffusers. These designs include an easily fabricated white-light diffuser and a uniform, high-NA diffuser design.

We describe the structure and fabrication of a one- dimensionally arrayed high density thermal-type micro fingerprint sensor. To provide thermal isolation, we designed and fabricated two sets of insulation cavities for each heater element, one for reducing the heat-transfer from the heater to the substrate, and the other one for that of heat to the wiring. The first set of cavities were etched under each heater bridge, leaving an SiO₂ diaphragm with the heater bridge on it, and laterally penetrating with the cavities of neighboring heater bridges. The second ones were etched at the both ends of each heater element, leaving a set of SiO₂- wiring bridges. This SiO₂-wiring bridge structure was used as a thermal isolator when performing a metal-film wiring. The wiring (an electrical feed-through) was formed by a lift-off method, and runs on the SiO₂ insulation surface from the heater element to the bonding pad through the SiO₂-wiring bridges. The fabricated sensor device was made on a (100) SOI (silicon-on-insulator) wafer. Each heater element was 5 X 17 X 50 (micrometer³) with a pitch of 80 micrometer. Because of its small thermal capacity and effective thermal isolation, the sensor element was very sensitive. When a 0.4- V/20-microsecond pulse-voltage was applied to the heater elements, their resistance reached a steady maximum value in about 4 to approximately 5 microseconds. This level of sensitivity will be useful in variety of thermal sensors, such as micro temperature sensors and micro flow sensors, in addition to the thermal-type fingerprint sensors.

This paper describes the design, fabrication and experiments of a micromirror array driven by electromagnetic force for right angle beam reflection to the vertical direction of the substrate. The device was fabricated using aluminum surface micromachining combined with nickel electroplating. The micromirror has couple of torsional springs enough long for 45 degree rotation, which angular deflection is necessary for right angle beam reflection. Also micromirror has a magnetic material for electromagnetic operation, and it has a mechanical stopper for angular deflection control. The main structural material is evaporated aluminum, and magnetic material is electroplated nickel. Thick photoresist is used as a sacrificial layer, and it is removed by oxygen plasma process. Electromagnetic characteristics were measured to find that about 10kA/m magnetic field intensity is needed for 45 degrees angular deflection. 25V to approximately 50V clamping voltage is required for selectively operation between the array within the external magnetic field. The dynamic response measurement was fulfilled using He-Ne laser and position sensitive diode (PSD). The lapsed time to reach 45 degrees is less than 0.5ms. But upward spring bending prevents the stopper from touching the substrate, so some oscillations corresponding to natural response is observed.

This paper deals with a work in progress concerning the fabrication of an insect-like microrobot. Thermal actuation has been chosen to move this microrobot, because of their large motions and their interesting density of energy. An integrated structure was chosen. Compliant thermal micro- actuators have been studied, fabricated and experimented. The characterization and modeling of these actuators have been done. Then, microlegs were modelized and designed with two degrees of freedom for each leg. The design of the microlegs and the operating cycle are given in this paper. Then the various stages of the microfabrication process are precisely described the microlegs are constituted of two thermal bimorphs connected together with a microbeam. Several microlegs are fabricated on one silicone wafer and bonded on a printed board to allow their activation. Their experimentation allows to give the results of each of the two degrees of freedom concerning the motions of these microlegs. Based on the results of these first experiments, the second generation of microlegs was conceived, made and tested, with the aim of decreasing the energy consumption. Then the next step will be the microfabrication of a new type of microlegs, before the whole structure of the microrobot including their legs in a monolithic way on one single silicon wafer.

For realization of a highly sensitive thermal microflow sensor with small active area of 100 X 100 micrometers ², a main interest is focused on decreasing thermal loss due to a substrate and air medium. A basic microstructure that was composed of a vacuum cavity with 6.2 micrometers depth and a stacked membrane was formed by the DECTOR (deep cavity using trench oxidation and release) process using silicon surface micromachining. On the vacuum platform, a n⁺-doped heater and two n⁺/p⁺-doped thermopiles with 1.0-micrometers -width poly-Si lines and Pt RTDs as major parts of the flow sensor were subsequently implemented by CMOS processing. The completed sensor had a microfluidics with a microchannel of 500(w) X 200(d) micrometers ². The thermopiles as main temperature sensors showed fast thermal response time of 68 microsecond(s) and maximum thermoelectric responsivity of 25 mV/mW. Flow measurements up to 430 sccm for air and 80 (mu) l/min for water revealed that the sensor outputs were significantly enhanced with the increase of the heater power and decrease of the distance between the heater and thermopile hot junction. Irrespective of a much smaller active area compared to bulk-micromachined thermal flow sensors, a high sensitivity of about 3.08 X 10^-2 mV/mW/sccm and 2.3 X 10^-2 mV/mW/((mu) l/min) was achieved for air and water as working fluid, respectively. Thanks to the vacuum platform and optimized sensor configuration, it is possible to improve flow sensitivity and to extend a linear flow range, accompanying with a reduced sensor size and low power consumption.

Novel highly integrated microreactors have been fabricated on silicon in order to dehydrogenate cyclohexane to benzene. There are 12 reactor chips on one single silicon wafer. The microreactor consists of three layers, which are reaction chamber integrated with heaters and thermal sensors, separation layer integrated with cantilever flowmeters and gas cover.

The electromechanical side-instability and the stable travel range of comb-drive actuators are investigated. The stable travel range depends on the finger gap spacing, the initial finger overlap, and the spring stiffness ratio of the compliant suspension. Proper design of the suspension structure is the most effective way to stabilize the actuator and therefore to achieve a large deflection. In this paper, an improved suspension design, so called tilted folded-beam suspension, is proposed. The expressions for the spring constants of the proposed suspension both in and perpendicular to the stroke direction are given. Using such suspension, the stability of the comb-drive actuator is improved and the stable travel range is enhanced. Comb drive actuators with various tilted folded-beam suspensions were fabricated using the standard surface micromachining technology and their operational performances were characterized. The experimental results are in good agreement with the theoretical predictions.

This paper presents an investigation focused on the formation of (311) planes by wet anisotropic etching of (100) silicon in 5% TMAH etchant. Atomistic model of (311) plane formation is proposed, suggesting that (311) planes are composed of (111) and (100) steps. Surface roughness that is in most cases consequence of hillock formation at low concentrations of TMAH and etch rates of (311) and (100) planes were studied as a function of etch temperature, time and addition of small amounts of ammonium peroxodisulfate (APODS). It was found that the smooth (311) planes without hillocks can be obtained only by etching in 5% TMAH with addition of 0,5% APODS. Due to obvious decomposition of APODS in the etching process determined by increased surface roughness, replenishing of additive is mandatory. Stirring experiments with 5%TMAH solution showed increased surface roughness and reduced etch rates of (100) and (311) plane. Dissolution rates of thermal oxide, LPCVD nitride and PECVD oxide and nitride were determined in temperature range from 60 degree(s)C-90 degree(s)C in 5% TMAH. APODS additive was found to have minor influence.

We propose the use of oxidized porous silicon as a low-loss substrate for the microwave devices. The oxidization of porous silicon is expected to increase the resistivity of Si surface layer and to reduce its effective dielectric loss, which would leads to a significant reduction of the nature loss of low-resisitivity (low-R) Si substrates under the microwave operation. In the present study, a significant improved microwave performance on low-R Si substrates has been demonstrated by measuring the microwave characteristics of coplanar waveguides fabricated on the Si substrates with thick oxidized porous surface layers.

The etching of single crystal silicon in ethylenediamine- pyrocatechol-water solutions (EDP) has been studied as a function of the composition of the etching solution. The solution with a constant composition of 7.5 ml of ethylenediamine (with 6g of pyrazine per liter) and 1.2g of pyrocatechol is used, and the water content is varied from 0 ml to 4 ml. Etch rate dependence on the active etching area is examined using three mask patterns having significantly different areas. It has been observed that etch rate depends significantly on the feature size in the solutions with higher water concentration and is almost independent of the area when the water content is 1 ml and below. Surface morphology was the other important criteria considered while optimizing the solution. Etch pit density (EPD) has been measured by etching the samples in different compositions to a constant depth of 45 micrometer. EPD is found to be high when the water content is above 2 ml and also when the amount of water is reduced below 0.5 ml. Minimal EPD is obtained when the water content is 0.5 ml. The optimized EDP solution containing 0.5 ml of water results in an etch rate of 44 micrometer/hr, independent of feature size and also good surface finish with EPD less than approximately 10³/cm².

SU-8 is a negative, epoxy type, near-UV photoresist. The resist has been specifically developed for ultrathick, high-aspect-ratio MEMS-type applications. It has been proven to be very sensitive to process variations. In this paper, the orthogonal method is used in the process. While three processing parameters are used as control factors, experiments are performed and results are evaluated. As the results being analyzed, a proposed fabrication process is derived from optimizing the control factors. The output structure has straight sidewall profile, fine line and space resolution, and strong adhesion to substrate. The aspect ratio can be greater than 20 in the 200-um-thick resist. Furthermore, several metallic films are used as the substrates. The titanium film with oxidation treatment is found to have the stronger adhesion to the resist. The result will open possibilities for low-cost LIGA-type process for MEMS applications.

Applications prospects for micro-electro-mechanical devices and examples of their design as electrostatic micro-relays, dilatometric sensors, and arrow indicator heads are presented in the paper. Fabrication of these devices is based on unique possibilities of alumina technology to form various design elements in a single monolithic part, as well as on high physical and mechanical parameters of anodic alumina.

Although dichromated gelatin (DCG) has a long history of photographic applications, the mechanisms of enzyme-etching gelatin and swelling effect have still not been satisfactorily explained. In this paper, we discuss the mechanism of DCG cross-linking and the swelling of gelatin in details. A refractive microlens array has been successfully fabricated by developing ammonium dichromated gelatin (ADG) in enzyme solution, the microlens' diameter is 19 micrometer, the height is 8 micrometer, and the focal height is 50 micrometer. The optimum technique parameters of this experiment process are presented and results are presented and evaluated by profile meter and interference microscope. This fabrication process shows the great potential for fabricating microlens array and micro-optics element (MOE) with DCG.