A model of infrastructure development for MEMS manufacturing Technologies is offered. The role of discontinuous innovation in achieving competitive advantage is briefly reviewed. This is followed by the development of a model that describes the stages in the growth of an infrastructure to support Micro-Electro-Mechanical-Systems infrastructure. We briefly describe how an infrastructure gradually grows to support a new industry, resulting from discontinuous innovation. the model indicates the evolving nature of the actions and investments that firms and governments need to make to support the growth of an immature industry. Consequently, we aim to not only offer a descriptive model, but offer guidance to firms on whether their intentions and resources fit with the state of the industry and to offer policy makers guidance on the timing of different types of support.

LIGA, an acronym from the German words for Lithography, Electroforming, and Molding, is being evaluated worldwide as a method to produce microparts from engineering materials. Much of the work to date in LIGA has focused on producing metal microparts, with nickel as the most common material of choice. There is a growing interest in producing plastic parts replicated from LIGA metal masters due largely to microanalytical instrumentation and medical applications. These plastic replicates are generally made by either hot embossing or injection molding. Ceramic replication, of particular interest for high temperature applications or to produce piezoelectric or magnetic microparts, is also emerging as an area of interest. In this paper, a model of the LIGA exposure and development processes is presented along with the result of numerical optimization of mask design and process cost. The baseline processes for a cost- effective method to produce metal microparts are discussed, along with replication methods and result for plastics and ceramics.

In the recent years micromolding has become one of the most important key technologies of microengineering. At the current state of art, the mass fabrication of plastic microparts for a wide range of applications like telecommunications, sensors, medical technology and biochemistry is feasible. Here a micro motor, plastic optical waveguides, a micro pump, and nanotiterplates are presented.

Micromolding is a key technology for the economic production of components for microsystems. It is applied in several manufacturing techniques including the LIGA process. Especially MicroInjection Molding allows cost-effective large-scale production of components for many applications to be used in microsystems technology. Using special molding machines, lateral dimensions in the micrometer range, structural details down to 200nm and maximum aspect ratios of more than 20 are achieved. Examples for applications are PSU-made housings for microfluidic systems or microcomponents made of PMMA for cardiac catheters. PC or LCP are appropriate materials for interconnection devices in microoptics and electronics. Other examples are injection molded lost plastic molds for electroforming or electroless plating of metal microstructures. An important economic factor is the optimization of the molding process and tool using different simulation techniques. Recently, novel techniques for manufacturing metal or ceramic microstructures were developed by adapting Powder Injection Molding to microtechnologies. Using commercially available feedstocks, microstructures were made of metals or ceramics. Rapid manufacturing of microcomponents is achieved by the so-called Photomolding process using reactive polymer resins as photocurable material and e.g. mold inserts fabricated by laser ablation. The addition of micro- or nanosized ceramics to the resin allows the molding of filled composite with enhanced mechanical properties. Subsequent debindering and sintering steps yield the pure ceramic microcomponents.

Microfabrication of sub-micron holes on 30 nm thick aluminum films on fused silica was investigated using pulse durations form 300 fs to 6 ns at 400 nm wavelength. Micromachined areas were investigate using atomic force microscopy for quality and size of features produced. Ablation diameters less than 400 nm was achieved with all pulse widths. Pulses less than 5 ps removed the films cleanly and left a flat- bottomed crater with no evidence of substrate melting over a wide fluence range.

Laser processing of metallic surfaces in use of fs pulse laser has been shown to produce novel effects. We demonstrate nanoscaled surface texturing effects of aluminum alloy 2024 using femtosecond pulse laser irradiation. The laser source is a 496 nm dye laser with 500 fs pulse width in a range of laser output fluence from 0.02 to 10 J/cm². Results indicate that the surface futures, ranging from nanoscale to 20 microns, can be developed through variation intensities. Advantages of femtosecond pulse laser for precise metal microstructuring and physical mechanisms for ultrashort pulse laser ablation have been discussed.

A wide variety of thin layer coatings have been reported for inhibiting the occurrence of post-release stiction in MEMS. Hydrophobic coatings such as self-assembled monolayers perform this function very well, but have a limited lifetime due to eventual generation of wear-induced damage. On the other hand, metallic oxides with superior wear resistance are hydrophilic in character, making them prone to stiction in humid environments. This paper describes the investigation of several dielectric materials as potential candidates for hydrophobic coatings with good wear resistant properties. Films were grown using a combination of vacuum deposition techniques, including enhanced variations of pulsed laser deposition. Contact angle and hardness measurements were performed on flat single crystal wafers for evaluation of film properties, and initial trials on a lateral friction test structure developed at Sandia National Laboratories were performed.

The ablation characteristics of the photoresist SU-8 under 248 KrF excimer pulsed laser radiation have been studied. The variation of SU-8 etch rate with fluence has been investigated in the range 0.05 J/cm² to 3.01 J/cm². Threshold fluence for ablation of SU-8 is measured to be about 0.05 J/cm². The etch rate of SU-8 is found to be higher than that of polyimide under identical conditions. The curves for etch rate dependence on fluence are in agreement with those reported in the literature for polyimides and also obey a theoretical model. We have investigated the effect of different prebake temperatures on the ablation characteristics which are found to be similar for all temperatures. The effect of increasing the number of laser shots has been examined at different fluences to understand the etch rate variation near the 'end of film' stage of ablation. The results of our analyses of these samples using SEM, profilometery and optical microscopy reveal - very smooth morphology of the etched surfaces without significant debris, no noticeable damage to underlying silicon, gradual build up of a carbonaceous film outside and around the etch pits. We find SU-8 very suitable for rapid excimer ablation lithography which has been demonstrated by patterning a gear structure in an SU-8 resist layer with aspect ration of 4.5.

A wide range of techniques have been developed recently for testing the mechanical properties of materials used in MEMS. Many of these techniques focus on uniaxial tension testing, while others address bending or torsional modes of deformation. This paper compares the two primary modes of testing - uniaxial tension and bending - in terms of the associated forces, deflections and sensitivities to uncertainty in geometry and loading. When determining elastic modulus, the bending test is shown to be more sensitive to uncertainties in beam cross section than is the tension test. On the other hand, in connection with strength characterization it is shown that small deviations form ideal uniaxial loading, either in terms of an offset from the neutral axis or an angular misalignment from the axis, can result in a large decrease in the apparent strength. Bending test for strength determination do not suffer such dramatic effects due to the misalignment of the applied loading.

SUMMiT at the Sandia National Laboratories' MDL is a standardized MEMS technology that allows designers to fabricate concept prototypes. This technology provides four polysilicon layers plus three sacrificial oxide layers to enable fabrication of complex mechanical systems-on-a-chip. Quantified reproducibility of the SUMMiT process is important for process engineers as well as designers. Summary statistics for critical MEMS technology parameters such as film thickness, line width, and sheet resistance will be reported for the SUMMiT process. Additionally, data from Van der Pauw test structures will be presented. Data on film thickness, film uniformity and critical dimensions of etched line widths are collected from both process and monitor wafers during manufacturing using film thickness metrology tools and SEM tools. A standardized diagnostic module is included in each SUMMiT run to obtain post- processing parametric data to monitor run-to-run reproducibility such as Van der Pauw structures for measuring sheet resistance. This characterization of the SUMMiT process enables design for manufacturability in the SUMMiT technology.

The ability to successfully release a Microelectromechanical system (MEMS) is a critical processing step of a MEMS device. Due to the inherent proximity of the moving structure and the surrounding surfaces, the final drying process can lead to 'stiction' of the structure that cannot be released. The amount of stiction on a surface micromachined polysilicon structure is dependent upon the various drying techniques employed. A comparison is made between a vapor isopropyl alcohol system, and a Marangoni drying system. The IPA system creates a meniscus at the bottom of the wafer and dries up, while the Marangoni system works in the opposite mode. Identical polysilicon test structures were used for the experiments. Experiments were performed with the IPA and Marangoni dryers using various MEMS structures to determine if there were increases in yields that were design dependent. The initial results obtained from these experiments indicate the Marangoni dryer increased the yield uniformity within a lot and lot to lot.

An important problem in silicon micromachining involves fabrication of suspended structures on a chip for both thermal as well as electromagnetic isolations. The problem becomes more pronounced as the size of a suspended structure increase. A new technique to remove the silicon from beneath a large structure, by micromachining for making a suspended microstructure both for thermal, as well as electromagnetic isolations on a CMOS chip is reported. Conventional methods require two steps; front-side etching, isotropic step, followed by an anisotropic etching step. An alternative technique is based on the backside etching process which requires extra masks and processing steps. In order to keep the post-processing steps to a minimum, a simple technique has been developed that exploits the front-side anisotropic etching to a create both under-cuttings as well as deep etching on one single step. This method uses the gate oxide and polysilicon layer in CMOS technology as the sacrificial layer for initiating the under-cutting needed to make a free standing microstructure. The micro-suspension thickness, width and length of 2 micrometers , 150 micrometers X micrometers , respectively, are made out of LPCVD oxide and have been fabricated.

Anisotropic etching of silicon creates different convex- corner undercutting contours in different varieties of etchant. This difference in undercutting configuration is investigated by analyses of the undercutting formation in detail. Based on Wulff-Jaccodine rules and some experimental results, theoretical analyses are given to clarify the reasons of different undercutting configuration caused by different etchant and the rationality of a certain plane occupying the undercutting position for a certain etchant. Furthermore, the investigation is lead to the convex-corner undercutting under maskless etching, i.e., during the etching mask on the structure removed. Experimental results show that the convex-corner undercutting under maskless etching is far different from that of conventional masked etching. The geometrical evolution of the undercutting is studied both experimentally and analytically. The compensation criteria for maskless etching are discovered and the corresponding compensation schemes are provided.

This paper reports on the fabrication of innovative counter electrodes for the development of a new Scanning Atom Probe (SAP) instrument. A process using thick spin-on dielectrics, deep reactive ion etching and photolithography has been developed for the realization of the counter electrodes. The novel structure is a two-terminal device in the form of a hollow cone shape, with tow electrodes separated by a dielectric layer. Different counter electrode design versions are presented, with the focus on the results for the first iteration. Electrical testing of the insulating layer is performed to investigate the material suitability for the operating conditions of the SAP instrument. Details regarding the design and fabrication procedure for the different designs, with emphasis on the process flow for the non standard steps, are also presented.

The integration of miniaturized mechanical components has spawned a new technology known as microelectromechanical systems (MEMS). Surface micromachining, defined as the fabrication of micromechanical structures from deposited thin films, is one of the core technological processes underlying MEMS. Surface micromachined structures have a large ratio of surface area to volume which makes them particularly vulnerable to adhesion to the substrate or adjacent structures during release on in use- a problem is called stiction. Since microactuators can have surfaces in normal or sliding contact, friction and wear are critical issues for reliable operation of MEMS devices. Surface modifications are needed to reduce adhesion and friction in micromechanical structures. In this paper, we will present a process used to selectively coat MEMS devices with Tungsten using a CVD process. We will discuss the effect of wet and vapor phase cleans along with different process variables. Endurance of the W coating is important, especially in applications where wear due to repetitive contacts with the film may occur. Further, tungsten is hard and chemically inert. Tungsten CVD is used in the integrated-circuit industry, which makes this approach manufacturable.

As Micro Systems Technology (MST) expands into new product applications, the present system used to align substrates will have significant impact on yield and product performance. A new technique that ensures the best possible alignment has been developed eliminating misalignment effects from temperature, shock and mechanical movement. This new approach called Laser Welding maintains the precision alignment advantage of setting or freezing substrate position using laser technology to form micro bond spots while the substrates are in the alignment system. The transport tooling is no longer required to maintain alignment with mechanical clamping. This technique will allow device and process designers to scale the requirements for aligned substrate bonding to new levels. At the same time it will dramatically reduce the risk of misalignment from the present transport tooling associated with processes that are at the end of a cumulative build.

The development of functional or smart materials for integration into microsystem is of increasing interest. An example is the shape memory effect exhibited by certain metal alloys which, in principle, can be exploited in the fabrication of micro-scale manipulators or actuators, thereby providing on-chip micromechanical functionality. We have investigated an ion beam sputter deposition process for the growth of TiNi shape memory alloy thin films and demonstrated the required control to produce equiatomic composition, uniform coverage and atomic layer-by-layer growth rates on engineering surfaces. The process uses argon ions at intermediate energy produced by a Kaufman-type ion source to sputter non-alloyed targets of high purity titanium and nickel. Precise measurements of deposition rates allows compositional control during thin film growth. As the sputtering targets and substrates are remote from the discharge plasma, deposition occurs under good vacuum of approximately 10^-6 mtorr thus promoting high quality films. Furthermore, the ion beam energetics allow deposition at relatively low substrate temperatures of < 150 degrees C with as-deposited films exhibiting shape memory properties without post-process high temperature annealing. Thermal imagin is used to monitor changes which are characteristic of the shape memory effect and is indicative of changes in specific heat capacity and thermal conductivity as the TiNi shape memory alloy undergoes martensitic to austenitic phase transformations.

This paper looks at the issues related to the integration of pressure sensors with the control circuit necessary to achieve the demands of increased performance measured by such parameters as linearity, resolution, accuracy and temperature sensitivity. In addition, the media in which these devices are used can influence the performance considerably with attendant offsets and drifts. Results of the effects of the media exposure on capacitive pressure sensors are presented. The motivation for integrating the sensor with the control circuit is then discussed with respect to these experimental results.

Work in materials other than silicon for MEMS applications has typically been restricted to materials such as metals and not more 'exotic' semiconductors. However, group III-V and II-VI semiconductors from a very important and versatile collection of material and electronic parameter variables available to the MEMS and MEMS designer. Thus, not only are the traditional mechanical material variables available, but also chemical constituents can be varied in ternary and quaternary materials. This flexibility can be extremely important for both friction and chemical compatibility issues for MEMS. In addition, the ability to continually vary the bandgap energy can be particularly useful for many electronics and IR detection applications. However, there are two major obstacles associated with alternate semiconductor material MEMS. The first issue is the actual fabrication of non-silicon devices and the second impediment is communicating with these novel devices. We will describe an essential material independent fabrication method that is amenable to most group III-V and II-VI semiconductors. This technique uses a combination of non-traditional direct write precision fabrication processes such as diamond turning, ion milling, laser ablation, etc. This type of deterministic fabrication approach lends itself to an almost trivial assembly process. We will also describe the mechanical, electrical, and optical self-aligning hybridization technique used for these alternate material MEMS.

High aspect ratio single crystal silicon resonant beams oriented with angles of 0, 11.25, 22.5, 33.75, and 45 degrees to the Si 100 direction were fabricated by using high density plasma etching and dissolved wafer techniques. The silicon was doped with boron with a concentration of >= 5 X 10¹⁹ cm^-3. The moduli of elasticity of the boron doped silicon were calculated from the measured resonant frequencies of the fabricated cantilever beams. They were approximately 1.56, 1.60, 1.66, 1.81 and 1.92 X 10¹² dyne/cm² with respect to the five different orientations mentioned above. These values are smaller than those calculated theoretically for intrinsic single crystal silicon. The built-in stresses in the clamped-clamped bridges were also found to be orientations. The stress variation is attributed to the variation of the modulus of elasticity and the difference in thermal expansion coefficients between silicon and the glass substrate to which the beam anchors are bonded.

A new interferometric method for trench depth monitoring in micromachining applications is presented. As compared to other interferometric techniques, this new method uses a Wollaston prism to generate two linearly polarized beams, which are recombined after reflection on the sample. This differential method, by taking advantage of the polarization properties of the light allows an accurate monitoring of the trench depth. New insights on interferometry are given, in particular it is shown that an optical model taking into account the effect of the mask evolution and its etching during the process leads to an improvement of the precision of the measurements. The application of this new interferometric method to two different processes is presented. This will show that real time Twin-Spot interferometry appears as a powerful technique for deep trench monitoring in micromachining applications.

ICP plasma etching is gaining widespread acceptance as an enabling micromachining technology for advanced MEMS fabrication. Whereas this technology has shown a capability of delivering multiple novel applications for R and D, its acceptance by industry for high volume production has been limited. This acceptance into production will only occur when the plasma etching equipment with this technology offers the device performance, throughput, reliability, and uptime criteria required by a production facility. The design of the plasma etcher using this technology and the process capability it consequently delivers, has significant implications in making this a reality. Alcatel has been supplying such a technology to this MEMS industry for over 5 years and in the interim has evolved its product and process to make this technology production worthy. Alcatel's next generation etcher, the Alcatel 601E, offers multiple advantages to MEMS manufacturers in realizing their production goals.

This paper reports advances in high-pressure, 3D laser chemical vapor deposition, which may be used to prototype insulating and metallic high-aspect-ratio microstructures. In this case, carbon was grown from ethylene at pressures of 1-11 bar; fine free-standing fibers of diamond-like carbon were grown at linear rates exceeding 120,000 microns per second. This record-setting growth rate allows the computer- controlled prototyping of centimeter-scale structures in only 15-20 minutes. The volumetric growth rate is scalable in pressure and laser power so that, with a single tool, micron-size details may be deposited as readily as large objects. The morphology, diameter, and steady-state growth rate of the carbon fibers were mapped versus the input laser power, the pre-cursor pressure, and the gas flow rate. Using a rotating mandrel, helical, tapered, and folded coils were grown at rates of 10-25 micrometers /s. Flat carbon coils were also grown by steadily increasing the radius of the laser focus from the mandrel while maintaining a constant tangential velocity. Tungsten fibers and single crystals were also grown from WF₆ and H₂ gas mixtures.

EFAB is a new micromachining process promising to rapidly and automatically batch fabricate high-aspect-ratio microstructures with arbitrary 3D geometry using inexpensive equipment. Conventional microfabrication processes have so far produced fairly simple geometries, yet many MEMS could benefit if more sophisticated shapes could be manufactured. By using 'Instant Masking' (IM) - a novel in-situ micropatterning method - to simplify, accelerate, and automate through-mask electroplating, EFAB can produce extremely complex shapes by depositing hundreds-thousands of layers at high speed. While other processes of the do not allow integration with ICs, EFAB operates at less than 60 degrees C, making IC compatibility a possibility. Alternative processes require costly facilities and equipment; EFAB separates photolithography from device fabrication, requiring a cleanroom only for mask-making, then depositing all layers in a low-cost, self-contained machine. All IM required can be prepared simultaneously, without repeating the lithography on each layer. Selective electrodeposition requires simply mating the mask with the substrate and applying current; in this way we have patterned well-defined features as small as 20 X 20 micrometers . The procedures in EFAB are selective electrodeposition, blanket electrodeposition, and planarization. To date we have built metal structures with up to 12 layers consisting of independently-moving components.

The SCALPEL lithography system combines the advantages of high resolution and wide process latitude of electron beam lithography with the throughput of a projection system. The SCALPEL approach has the potential to meet the minimum feature size requirements of future IC generations down to 50 nm.

This paper describes a 10-mask process for fabricating single crystal, surface micromachined devices by using porous silicon as a sacrificial layer, and an n-type epitaxial layer for structural material. Single crystal structures have the important advantage over polysilicon structures of precisely controlled material properties, in particular Young's Modulus and residual strain. Additionally, the epitaxial layer is suitable for integrating circuitry, and provides a promising alternative for integrated microsystems. This results in a process with similar flexibility in device design to a polysilicon surface micromachined process, but with the control of a bulk silicon technology. The process also includes provisions for device encapsulation in vacuum using reactive sealing of the microstructure with an LPCVD polysilicon layer. Although this technology is versatile and can be used for a variety of microstructures, the primary demonstration vehicles used in this research effort have been resonators. Some of the key problems is using porous silicon processes include: dimensional control of the porous silicon region; creating a high aspect ratio porous silicon region; eliminating defects induced by the porous silicon process in the remaining silicon structure; and protection of the oxidized porous silicon from etching prior to sacrificial etch.

Ion Chromatography has already shown its value as a process monitoring and troubleshooting tool for the semiconductor and disk drive manufacturers. Similarly, there are many possible uses for this analytical technique in the manufacture of microelectromechanical devices. Some of these uses are: (i) the analysis of corrosive ions in ultrapure water and ultrapure chemicals; (ii) analysis of plating bath constituents and contaminants; (iii) analysis of corrosive ions found on MEMS devices during manufacturing and which can later cause device failure of reliability problems; (iv) the analysis of corrosive ions found on MEMS manufacturing tools, carriers and other materials that come in contact with the final product. This paper will explore the many uses of ion chromatography for the manufacture of MEMS devices. Special techniques, only recently developed for use on very small objects, will also be presented for the analysis of ions at part per trillion levels.

We have investigated the effects of metal impurities and thermal oxidation process on Si anisotropic KOH etching characteristics for fabricating microsensors and microactuators having precise deep narrow grooves or channels. The effect of metal impurities such as Al, Cr, Fe, Pb and Cu are evaluated using 30 wt percent KOH etchant at 60 degrees C. Al, Cr and Fe have no relation to the etching characteristics, however, Pb and Cu strongly affect the etching characteristics. The etching rate of Si decreases with increasing Pb and Cu concentration. The etch rate selectivity , which is an anisotropy ratio defined by the etch rate ratio of (110) and (111) plane, is not changed by Pb impurity, but extremely decreases with increasing Cu impurity. It dips form 150 to 80 when the Cu concentration is over 50ppb, and saturated over the concentration. With respect to the surface roughness within our evaluated metal impurities, Cu impurity also strongly affects the roughness of the etched surface. In addition to the effect of metal impurities, we have experienced the effect on the etching selectivity by the thermal oxidation process. The selectivity is decreased with repeating thermal oxidation process, and this tendency is more pronounced with higher oxygen concentration of evaluated Si wafers. As a result, controlling Cu impurity concentration and using a low oxygen concentration wafer are crucial considerations when fabricating sensors and actuators with narrow grooves or channels by Si anisotropic KOH etching.

We present a new material for highly resistive heaters: thin Ti/TiN layers. Their resistivity is indeed comparable to the resistivity of NiCr, i.e. 50-100 micro-Ohn-cm. However, as opposed to the latter material, Ti/TiN is CMOS compatible and thus easier to incorporate in CMOS integrated MEMS processing. To test the reliability of thin Ti/TiN resistive heaters, both 5 nm Ti/30 nm TiN and 5 nm Ti/60 nm TiN heaters were fabricated. A thermal analysis shows a small temperature coefficient of resistivity. To test the reliability of such heaters at temperatures up to 300 degrees C, 1 micron wide Ti/TiN lines were biased using high currents. Both DC and pulsed DC current stressing resulted in very small deviations from the initial resistance for sintered and passivated heaters. The temperature uniformity over the heater line is investigated using Emission Microscopy.

Due to the rapid advancements in the data storage market, the development of new technologies and mechanisms are needed to support the continued growth of data storage systems. The concept and technology of Micro Electro Mechanical Systems (MEMS) can provide opportunities to meet these demands. Correspondingly, new MEMS devices can be made commercially available by sharing the benefits of developments in data storage systems. The photolithography requirements for thin film head (TFH) processing have grown increasingly challenging. Specifically, the resolution of submicron isolated features is required in thick photoresist; resulting in aspect ratios of nearly 10 to 1. To satisfy these imaging requirements, the use of i-line reduction lithography tools with variable numerical aperture and partial coherence are necessary. This study examines the influence of NA, (sigma) , and reticle bias on critical features in a typical TFH write-layer process. Combinations of NA and (sigma) were investigated for their impact on minimum feature size, process latitude, and sidewall angle. Process latitude was quantified for each illumination condition over a range of focus and exposure conditions.

The commercialization of microfabricated devices requires an efficient, high yield manufacturing process. This paper demonstrates that the extension of scanning projection lithography into the manufacture of microscale devices presents an opportunity to develop cost effective processes. The use of thick dry film resists is a well characterized process. The technology associated with lamination and development is fully commercialized, and the process requirements for exposure allow great operational flexibility. Examples of the use of this technology to form microscale typical of MEMS devices are presented for a resists thickness of 30 micrometers . Microphotographs of the resulting features are presented, and the achievable resolutions and wall angles are quantified. An analysis of process economics for using thick film resists to generate MEMS feature at a commercially viable scale is presented. The factors influencing throughput are discussed, and the potential advantage of using a scanning projection tool with these resists is presented.

The LIGA process, which combines x-ray lithography with electroplating and modeling, is a world wide used technique for the fabrication of high aspect ratio microstructures. In the first step a resist layer, typically PMMA, which is applied to a metal coated substrate, is patterned by shadow printing through a x-ray mask with synchrotron radiation. The exposed parts are subsequently dissolved in an organic developer. The achievable quality of the microstructure is decisively defined by the development process. In order to define an effective development process and create a simulation tool, which allows to foretell the needed development parameters and the achievable quality already at a design stage, the development behavior and its influencing parameters need to be investigated. Much work has been done in this area. In these previous studies, the development rate was either studied using PMMA foils in which a homogeneous dose or a dose profile has been deposited, or using irradiated microstructures. In the first case, result obtained by ex-situ measurements show, that the development rate is a bare function of the dose. In case of irradiated microstructures, the experimentally obtained development rate was described as an empirical function of the dose value and depth of dose deposition. The aim of this work is to investigate the difference in the development behavior of a microstructure compared to a foil and to link the results. Therefore, using in-situ measurements, we have made experiments using foils and microstructures with crosslinked and non-crosslinked PMMA covering a wide dose range. The final purpose is to find a relation between dose and development rate to determine the necessary development time of a sample with a given dose profile, with high precision. Experiments, result and simulation of the development rate, for the two kinds of materials are presented and discussed.

Radiological imagin relies heavily on collimators to achieve diagnostic x-ray images. These collimating structures are required due to the lack of efficient x-ray reflectors or refractors needed to make lenses or mirrors. In order to achieve higher resolution x-ray images, finer collimator geometries are needed. The two critical parameters that define the fineness of a collimator are the length of the collimator structure and the aperture size. Current collimator fabrication technology provides structures with coarse cell sizes, which require long structural lengths, to achieve image optimization. Finer collimator geometries would help reduce the overall length of collimating structures. Tecomet, of Woburn, MA has developed a new technology to fabricate fine-featured, high aspect ratio structures made from high Z materials. These collimating structures have been made from tungsten with aspect ratios above 50:1 and geometry features less than 20 microns. This technology has enabled advancements in the design of x-ray coded apertures. This has opened the door to new ideas for x-ray imaging. Optimization coders, made from tungsten, can now be designed and fabricated to achieve very high angular resolution. Significant reduction in weight is realized due to the reduction in collimator thickness. The collimators made using these fabrication methods also provide greater long-term structural stability compared to collimators used in diagnostic x-ray imaging using lead.

Images formed in thick photosensitive materials are widely used as electroplating molds for micro-electromechanical (MEMS) part and other electronic applications such as bump bonding, thin film heads and multichip module manufacturing. The expansion of traditional microelectronic lithography into very thick photoresists present a technical challenge for stepper manufacturers that have traditionally attempted to optimize resolution and depth of focus for thin photoresist systems. Stepper optics and illumination needs to be re-optimized for the best performance in thick photosensitive materials.

We fabricated 2D subwavelength structured (SWS) surface on crystal silicon and SiO₂ substrates. The SWS surface patterns were generated by electron beam lithography and etched by SF₆ fast atom beam. In the case of the silicon SWS surface with the period of 150nm, the grating had conical profile and the groove was approximately 350nm deep. The reflectivity was examined at the wavelengths between 200nm and 2500nm. At 400nm, the reflectivity decreased to 0.5 percent from 54.7 percent of the silicon substrate. The reflectivity was also examined for the incident angel with He-Ne laser light. Thus, it was shown that the silicon SWS surface prevented the reflection in the wide ranges of wavelength and incident angle. We also fabricated the hole type SWS surface and the column type SWS surface on silicon substrates. In both types, the grating period was 200nm and the grooves were approximately 275nm deep. Moreover, the SiO₂ SWS surface with the period of 150nm was fabricated and the reflectivity was examined at the wavelengths between 200nm and 2500nm.

This paper has advanced a kind of micro electromagnet motor with low rotational speed and high torque output: top-face- sway micro electromagnet motor. Its working principle is as following: under the rotating electromagnet's force, the motor's cone shape rotor makes pure rolling on the inner cone face of the stator and thus the output axle's rotation comes into being. Through testing, its rotation ranges is 20-860 rpm with larger than 10 (mu) Nm torque output. The result of the experiment show that with the same input power, this kind of micrometer has larger torque output than others' with the same volume. It has a wide applying prospect.

We have been investigating microforming techniques suitable for fabricating metal microcomponents. In this study, we used a microcutting-technology system equipped with a newly designed special shape cutting tool. As the shape of ordinary end-mills is complex, small dimensional sizes are more difficult to fabricate. This means that the microcutting of 3D components is also difficult. To overcome this problem, we proposed a simple oblique-cut micromill to be used exclusively for micromachining. A precision cutting device was also designed. The oblique-cut micromill is driven by a high-speed spindle motor of 50,000-10,000 rpm supported by air bearings. Results of experiments show that certain micropatterns can be fabricated on aluminum wire. Narrow parts of patterns that are 15-25 micrometers wide can also be fabricated. These results indicate that the system can be used to create 3D free-form micropatterns. In this paper, we report the result of the development of the micromill, machining system, and some fabricated items.

Numerical simulations have been done to delineate transport effects on the electrodeposition of heavy ions in the deep cavities typically fabricated by the LIGA process. Both forced convection and buoyancy-driven natural convection have been considered. Flow patterns and deposition rates have been calculated for a range of electrode reaction rates, forced flow Reynolds numbers, Rayleigh numbers and cavity aspect ratios. The results show that free convection is a significant player in the transport-limited regime, and substantially increases deposition rates, even for modest Rayleigh numbers. For high Rayleigh numbers, the flows are found to be unsteady, and may further increase deposition rates.

New methodologies in anisotropic wet-chemical etching of oriented silicon allowing useful process designs combined with smart mask-to crystal-orientation-alignment are presented. The described methods yield smooth, etch-step free surfaces as well as high-quality plan-parallel beams and membranes. With a combination of pre-etching at different depths and passivation steps, structures can be etched at different levels in a wafer. Design rules using the < 100 >-crystal orientation, supplemented with examples demonstrate the high potential of using < 100 > oriented wafers in microsystem design.

Silicon doped by thermal diffusion from Boron⁺ solid source at different temperature employing both dry and wet processes was obtained for bulk micromachining applications. It could observe that the surface morphology was strong influenced by temperature and ambient-related effects are non-important. For low annealing temperature, the prominent effects are due to segregation phenomena of boron in silicon. At higher temperature impurity segregation is inhibited and the defects formation becomes the main effect. For B⁺ diffused layers at 1100 degrees C on dry oxygen ambient for 60 min. we obtained a uniform redistribution of the defects and the size is reduced. The redistribution of the defects is correlated with the surface roughness studied by atomic force microscopy and optical microscopy.

At high boron concentration, silicon shows a severe reduction of the etching rate in alkaline solutions, property which is largely used for achieving etch-stop zones for bulk micromachining. The desired boron concentration can be reached in silicon by thermal diffusion or by ion implantation. In an attempt to extend the bulk micromachining techniques over germanium, we verified that boron also reduces the etch rate of this material - this time, in acidic solutions. Doping germanium by diffusion being far from a standard technology, we found ion implantation a better-suited doping process. Experiments and simulations were made to draw the process parameters for controlling the boron concentration and its distribution in germanium. The germanium wafers were implanted through a lithographic structured resist layer. The annealing of the implanted Ge took place in N₂ atmosphere, at 700 degrees C. We succeeded putting into evidence a reduction of the etch rate of Ge in a H₃PO₄:H₂O₂:C₂H₅OH solution in the implanted area, relative to the non- implanted one. The effect is similar to that in silicon. As a parasitic phenomenon, during the anisotropic etching, the roughness increased more on the implanted areas, where the defect-related typical square pits were of higher depth and size.

Our researches were devoted to the micromechanical elements fabricated by the surface micromachining technology, in order to reduce or to eliminate the internal stress or the stress gradients. We used an analysis based on secondary ion mass spectroscopy and the spreading resistance profiling determinations, correlated with cross-section electron transmission spectroscopy. The stress induced in the polysilicon layers by the technological processes depends on: (i) the conditions of the low pressure chemical vapor deposition process; (ii) the phosphorus doping technique; (iii) the subsequent multi-step annealing processes. In our experiments the LP-CVD conditions were maintained the same, but the condition specified previously as items (ii) was varied by using two different doping techniques: thermal- chemical doping consisting in prediffusion from a POCl₃ source in an open furnace tube; ionic implantation with an energy E equals 65KeV and a dose N equals 4.5 X 10¹⁵ cm^-2. The implantation process was followed by an annealing at 900 degrees C in an oxygen ambient for 30 minutes. The thermal budget was varied after the doping in order to reduce the stress gradient in the polysilicon layers. The results of our analysis allow us to show that: (1) the doping gradients are correlated with the slower phosphorus grains forme by an excess of the oxygen atoms; a concurrent process induced by the silicon self-interstitial injection during the diffusion and oxidation, determines the enhancement of the grain growth and therefore the enhancement of the electrical activation especially near the internal polysilicon interface; (2) the post-doping annealing conditions could be varied in a convenient manner, so that the doping induced stress gradients into the polysilicon layers to be reduced or completely eliminated for suitable micromechanical induced stress gradients into the polysilicon layers to be reduced or completely eliminated for suitable micromechanical applications. The results were used for the process optimization of micromechanical elements. The internal stress was determined by using anew, pull-in voltage method, allowing the comparison of the theory with the experimental data. It was deduced a new form of the equations set useful to extract the mechanical parameters like the internal stress and the Young's module. It was also deduced a simplified approximate formula useful to apply the least square fitting method for the extraction of the mechanical parameters. The results confirms the conclusions of the doping and the structural analysis.

High sensitivity is a basic requirement for a new generation of thermal detectors. To meet the requirement, close-packed, 2D silicon detector arrays have been developed in NASA Goddard Space Flight Center. The goal of the task is to fabricate detector arrays configured with thermal detectors such as IR bolometers and x-ray calorimeters to use in space flight missions. This paper focuses on the fabrication and the mechanical testing of detector arrays in a 0.2 mm pixel size, the smallest pop-up detectors being developed so far. These array structures, nicknamed 'PUDs' for 'Pop-Up Detectors', are fabricated on 1 micrometers thick, single-crystal, silicon membranes. Their designs have been refined so we can utilize the flexibility of thin silicon films by actually folding the silicon membranes to 90 degrees in order to obtain close-packed 2D arrays. The PUD elements consist of a detector platform and two legs for mechanical support while also serving as electrical and thermal paths. Torsion bars and cantilevers connecting the detector platform to the legs provide additional flexures for strain relief. Using micro- electromechanical structure fabrication techniques, including photolithography, anisotropic chemical etching, reactive-ion etching, and laser dicing, we have fabricated PUD detector arrays of fourteen designs with a variation of four parameters including cantilever length, torsion bar length and width, and leg length. Folding test were conducted to test mechanical stress distribution for the array structures. We obtained folding yields and selected optimum design parameters to reach minimal stress levels. Computer simulation was also employed to verify mechanical behaviors of PUDs in the folding process. In addition, scanning electron microscopy was utilized to examine the flatness of detectors and the alignment of detector pixels in arrays. The fabrication of thermistor and heaters on the pop-up detectors is under way, preparing us for the next step of the experiment, the thermal test.

There has been much attention devoted to microfluidic systems in recent years, and it has become clear that electrokinetics is one of the favored methods to drive systems with flow channel dimensions in the tens of microns and flow rates in the nanoliter per second range. At these small dimensions, sample and reagent consumption is very small, and analysis speeds are greatly improved. At Caliper, we have demonstrated applications including DNA separations, enzyme assays, and cell biology. Others in this field have shown other examples of applications, such as immunoassays on a chip. The trend in electrokinetically driven microfluidic circuits is toward more complexity and functionality, which has mostly been achieved through the use of parallelism. It is tempting to regard this as an extension of Moore's law, which predicts a constant rate of increase of the functionality of an electronic integrated circuit. This raises the issue of the scaling laws governing microfluidic circuits, and what the limits are the scaling will run into. This presentation will discuss the scaling laws for simple circuits such as a four-port device for injection and separation, followed by an analysis of the design issues involved in parallel devices.

3D photonic lattices are engineered 'materials' which are the photonic analogues of semiconductors. These structures were first proposed and demonstrated in the mid-to-late 1980's. However, due to fabrication difficulties, lattices active in the IR are only just emerging. Wide ranges of structures and fabrication approaches have been investigated. The most promising approaches have been investigated. The most promising approach for many potential applications is a diamond-like structure fabricated using silicon microprocessing techniques. This approach has enabled the fabrication of 3D silicon photonic lattices active in the IR. The structures display band gaps centered from 12(mu) down to 1.55 (mu) .