Pyramidal metal tips which are fixed to a silicon cantilever have proven to be very powerful probe tips in electrical Atomic Force Microscopy (AFM). Although silicon is currently the cantilever material of choice for most applications, solid metal cantilevers are an interesting alternative due to their higher electrical conductivity and a more simplified fabrication procedure. Therefore, we have developed a process scheme for such full metal probes and evaluated them in AFM. This paper discusses the fabrication scheme in detail and presents first results concerning the application of the fabricated probes for semiconductor device analysis. Our experiments clearly show that operational full metal probes can be made on a large scale in a 150 mm silicon wafer technology. Using the optimized process, full metal probes can be fabricated which can compete in contact-mode AFM with pyramidal metal tips fixed to a silicon cantilever. Our work is currently focussing on further improvement of batch reproducibility.

In this paper a design of thermal actuators for out-of-plane displacements for parallel Scanning Tunneling Microscope (STM) applications in a standard 0.5 micrometers 3-metal CMOS process is presented. Micromachined STM tips have potential applications in data storage, lithography and high sensitivity microsensors. Standard CMOS process allows for low cost integration of on chip electronics with microstructures. The STM tip actuator consists of a multilayer micromachined beam constructed of various combinations of metal and oxide layers of the CMOS process. Polysilicon is used to heat the multimorph to achieve tip deflection. The tip deflections are a function of the beam design parameters, such as different combinations of metal and oxide layers, and beam length. Analytical results for heat distribution within the multimorph structure are presented along with thermo-mechanical finite element simulations based on previously obtained material properties for the process and experimental results. The validation of this design methodology allows design of STM actuators with desired specifications. The maximum out-of-plane displacements for the 115 micrometers long multimorph actuators with different metal and oxide layer combinations range from 0.5 to 10.0 micrometers for an input power of 10 mW. Spurious in- plane motions of thermal actuators due to mask misalignments in the standard CMOS process are limited by design. The out of plane curling of the actuators varies from 1.65 to 15.75 micrometers depending on beam composition. The maximum power dissipation for all actuators was less than 25 mW.

In this paper the authors would like to demonstrate, using Atomic Force Microscopy (AFM), the effects of parameters such as probe current on the micromachined profiles produced by focused ion beam. We will compare these results obtained with AFM with those using scanning electron microscopy. Control of these parameters in the fabrication of nanostructures on different substrate materials such as metals and semiconductors will also be demonstrated.

Design, manufacturing and test of microcomponents generate new challenges for measurement techniques in general. The non-contacting operation of optical metrology makes it attractive to solve the task of measuring geometric quantities of microparts. So far, speckle interferometry (ESPI) is well established as a measuring tool for analyzing deformation, vibration and strain on a macroscopic level. This paper deals with possibilities and application limits of ESPI in the case of scaling down the object size below one millimeter.

Micromachined beams are commonly used to measure material properties in MEMS. Such measurements are complicated by the fact that boundary effects at the ends of the beams have a significant effect on the properties being measured. In an effort to improve the accuracy and resolution of such measurements, we are conducting a study of support post compliances in cantilever and fixed-fixed beams. Three different support post designs have been analyzed by finite element modeling. The results are then compared to measurements made on actual devices using interferometry. Using this technique, the accuracy of measurements of Young's modulus has been improved. Continuing work will also improve the measurement of residual stress.

Microelectromechanical systems (MEMS) have been around for many years. However, reliability issues, increasing costs, and die sizes are pushing the technology beyond its current capabilities. Integrating a micromachined sensor with its control circuitry on a single piece of silicon offers a cost and a performance advantage over the conventional two chip sensor. The enhancements offered by an integrated MEMS device are leading to many new challenges. The ability to encapsulate the MEMS device without affecting the integrated circuit is a key concern. One method of hermetically sealing the MEMS uses a frit glass which can cause potential damage to the integrated circuit because of the sealing parameters used. In standard CMOS processing, the integrated circuit is not subjected to high temperatures once the devices are built, whereas in wafer level packaging, high temperatures are involved. The high temperatures and the glass composition associated with the sensor capping process could be detrimental to these devices. A test vehicle was developed, therefore, to evaluate the compatibility of the CMOS and the sensor capping processes. The electrical results suggest that the glass and bonding process do not degrade the transistor performance.

Anisotropically etched silicon structures were impacted against stainless steel to measure relative impact strength of different silicon surface treatments. In order to study the effects of surface treatment, the beams were coated with thermal silicon dioxide, LPCVD silicon nitride, and silicon dioxide/silicon nitride sandwich. A jig was made to controllably impact the sample and also measure the stresses during impact. It was found that silicon-dioxide treatment resulted in the highest strength structures and the nitride coated samples being weaker than even the uncoated sample. An explanation based on surface stress effect on crack initiation is presented.

The fabrication of thick polysilicon films for MEMS transducer devices has significant impact on manufacturing process cost and cycle time. Standard polysilicon processing for films greater than two microns result in prohibitive cycle times for production. This study investigates the effect of deposition conditions on film morphology and mechanical properties and manufacturability for 3 micrometers polysilicon films. The study investigated deposition temperatures ranging from 580 degree(s)C to 1050 degree(s)C, gas flow rates, and deposition pressures on across-wafer and across- load uniformity, film morphology studied using AFM, XRD, and TEM, and blanket film intrinsic stresses. The goal was a high deposition rate low residual stress polysilicon film with morphology resembling the standard polysilicon deposition process. The study demonstrated that film morphology was stable between 605 degree(s)C and 700 degree(s)C with a transition in film properties occurring above that temperature. Intrinsic stresses followed the expected trends with compressive films above 603 degree(s)C. Increasing temperature and pressure resulted in increased deposition rates and decreased across-wafer and across-load thickness uniformities. No attempt was made to optimize the processes or hardware configurations to improve uniformities. The process investigation demonstrated increased deposition rates with acceptable as-deposited film morphology and intrinsic stresses. The study confirmed morphology and stress trends with pressure and temperature.

We have designed, fabricated, tested and modeled a first generation small area test structure for MEMS fracture studies by electrostatic rather than mechanical probing. Because of its small area, this device has potential applications as a lot monitor of strength of fatigue of the MEMS structural material. By matching deflection versus applied voltage data to a 3D model of the test structure, we develop high confidence that the local stresses achieved in the gage section are greater than 1 GPa. Brittle failure of the polycrystalline silicon was observed.

Micro-oscillators of different designs and dimensions have been fabricated for use in a nuclear magnetic resonance force microscope. The various designs include double and triple torsional oscillators which have high Q's at room temperature (approximately equals 10,000) when operating at the upper cantilever and upper torsional resonances. Depending on design and dimensions, the resonance frequencies vary from tens to hundreds of kHz. Typical dimensions of the designs are (200 X 150) micrometers ² X 200 nm thick. To fabricate these devices, microelectric fabrication techniques were employed. Si (100) wafers were patterned, etched, and boron-implanted at a dose of 4.2 X 10¹⁶ cm^-2 and an energy of 134 keV. A post-implant anneal was then performed at 1000 degree(s)C, followed by a KOH wet-etch which leaves the free-standing boron-doped oscillators. Depending on the doping level, anneal, and etch parameters, the thickness of the oscillators varies from 100 - 400 nm. In order to optimize the design and fabrication process, resonance frequencies and Q's have been characterized using fiber-optic interferometry. For example, the upper cantilever resonance of one design has been found to have a minimum detectable force of 1.5 X 10^-16 N/(root)Hz at room temperature.

In this research, the authors have proposed and developed a new manufacturing process for giant magnetostrictive material (GMM) by using powder metallurgic technique. The results obtained in this paper have verified that the powder metallurgic GMM is quite comparable to that made by the well-established Bridgman Method, in terms of large magneto strain, low hysteresis and high repeatability, and yet at one-third cost. More important is that the powder metallurgy is able to achieve a near-net-shape product regardless to the complexity of the geometry and dimension of the size. It opens new possibilities to miniaturize the sensors and actuators down to millimeter or sub-millimeter scale. Using the Joule effect and the inverse Wiedemann effect, a GMM pump and torque sensor have developed in this research to show the potential usage of the powder metallurgic GMM in practical applications.

Laser induced photo-polymerization is rapid prototyping technique for the manufacturing of high aspect ratio micro- mechanical parts. The process consists of UV laser-induced polymerization of multifunctional monomers. This photo- forming method has advantages of speed and economy over other methods used in the manufacturing of high aspect ratio microstructures. However, current photo-forming systems do not yet have the accuracy and resolution required for micro- mechanical fabrication. To achieve a system with high resolution, it is desirable to develop a predictive mathematical model that can be used in process optimization. In this study, we develop a mathematical model that predicts the laser beam pixel dwell time (or the scanning scheme) on the monomer layer for attaining uniform monomer conversion or solidification by which one can achieve dimensional accuracy and smooth surfaces of the microstructure.

SiO_x-containing DLC films are deposited by plasma enhanced chemical vapor deposition on Si substrate. The effect of SiO_x dopants on the stress, adhesion and hydrophobicity of the DLC films are studied. The incorporation of SiO_x in the DLC films deposited by using hexamethyldisiloxane and CH₄ mixture reduces the residual stress as well as enhances adhesion of the film on the substrate. Besides, the thermal stability of the film also improves.

Fluorine (F₂) lasers emit at 157 nm, the shortest commercially available laser wavelength. Innovations such as NovaTube^TM technology have resulted in powerful, highly reliable and cost effective F₂ lasers. This paper will discuss the most recent F₂ laser developments, resulting in repetition rates up to 1000 Hz and pulse energies in excess of 25 mJ. The industry now considers F₂ lasers to be the next step (after ArF at 193 nm) in key technologies such as lithography and micromachining.

The usefulness of thin (< 250 micrometers ) rigid graphite plates as x-ray mask substrates for micromachining and LIGA applications has been demonstrated. Rigid graphite offers unique properties, such as moderate x-ray absorption and optimal filtration of synchrotron radiation, relatively low cost, compatibility with additive (electroplating) and subtractive (etching, micromachining) processes for absorber patterning. The surface roughness of these substrates is associated with the inherent porosity of a commercially available rigid graphite material (typical R_a values are in the range of 1 - 2 micrometers ). The surface roughness of this rigid graphite sheet is reduced down to a 0.1 - 0.2 micrometers R_a value by polishing. To reduce surface roughness further and make the substrate usable for fine e-beam or optical absorber imaging, additional smoothing is required. In this paper, the surface characteristics of rigid graphite sheets are analyzed and a glazing technique developed to smooth the graphite surface is described. This technique employs hard baking process of novolac-based resins. An average R_a roughness value of approximately 5 nm was obtained after 5 coating using novolac-based AZ type resist.

The availability of high-energy, high-flux, collimated synchrotron radiation has extended the application of deep X-ray lithography to thickness values of the PMMA resist of several millimeters. Some of the most severe limitations come from plastic deformation, stress, and cracks induced in PMMA during exposure and development. We have observed and characterized these phenomena quantitatively. Profilometry measurements revealed that the PMMA is subjected either to local shrinkage or to expansion, while compression and expansion evolve over time. Due to material loss and crosslinking, the material undergoes a shrinkage, while the radiation-induced decomposition generates gases expanding the polymer matrix. The overall dynamics of the material microrelief and stress during and after the exposure depend on the balance between compaction and outgassing. These depend in turn on the exposure conditions (spectrum, dose, dose rate, scanning, temperature), post-exposure storage conditions, PMMA material properties and thickness, and also on the size and geometry of the exposed patterns.

In this paper, a prototype of 2 mm-diameter micro-cycloid gear system fabricated by the multi-exposure LIGA technique is presented. The entire gear system consists of a casing and three vertically stacked disks and gears. Each part is composed of three different levels. The first level, 40 micrometers high, was fabricated by UV-lithography, and the second as well as the third level, 195 micrometers and 250 micrometers high respectively, were processed by aligned deep X-ray lithography (DXL). The alignment error between two DXL- processed layers was measured, and the results have turned out to be within +/- 5 micrometers range. As a result of the height control process by the mechanical surface machining, the deviation of structural height has been maintained within +/- 3 micrometers range for the UV-lithography-processed structures, and +/- 10 micrometers for the DXL-processed structures. Further the tests of gear assembly were implemented with 125 micrometers -diameter glass fiber, by using a die-bonding machine with vacuum gripper under stereo- microscope. Finally the dynamic tests of the gear system were successfully conducted with the mechanical torque input by an electrical motor. A proper rotational speed reduction was observed in the operational input range of 3 to 1500 rpm with the designed gear ratio of 18.

Micromechanical devices have just entered out everyday life and have a wide range of applications in the near future. Therefore a strong need arises for elaborate study on reliability of micromechanical structures under various conditions and environments. Silicon nitride is one of the basic structural materials in MEMS devices due to its good mechanical properties. Extreme aspect ratio structures like long cantilevers or large membranes are often built of thin silicon nitride films. They serve mostly as mechanical supporting components forming multilayer structures. Precise characterization of the mechanical properties is required for proper design and reliable device operation. Atomic force microscope was utilized for measurement of Young's modulus and spring constant of silicon nitride cantilever beams. Static and dynamic accelerated aging tests were conducted in order to predict the long-term behavior of the structures. Two reversed failure mechanisms were found during the aging tests, both substantially effecting the device operation.

This paper reports a study of the relationship between internal stress and deformation of diaphragm at elevated temperatures using scanning electron microscope. It is necessary to make a flat diaphragm in order to obtain good performance for various diaphragm-type sensors using heat transfer, such as flow sensors and accelerometers. When these sensors are used in high temperature environments, a flat diaphragm is required. Therefore, it is very important to observe and control the deformation behavior of a diaphragm at various temperatures. As far as we know, few results have been reported on the observation of deformed diaphragms at elevated temperatures.

We have developed and tested a tunneling tip engine in a multi-sensor module. The tested flip-chip device uses tunneling current for feedback to control deformation of a micromachined pressure membrane. The device includes a tunneling acceleration sensor based on a similar `seesaw' structure, but this paper only reports on the membrane structure. Several intermediate test beds were designed to characterize the strength and the mechanical properties of the membrane. The data collected from these experiments were used in simulation of the sensor structure prior to final fabrication. The resulting sensor, which uses the feedback actuation signal as the sensor output, is designed for closed loop control of the tip electron tunneling current. This type of closed-loop implementation provides better linearity and dynamic range than that of open-loop sensors.

A more robust XPM with improved thermal and radiation stability was designed and fabricated in CNTech. The effectiveness of this design is demonstrated and XPM fabrication processing is optimized to obtain finer control over the processing, low stress membrane and vertical sidewall in the phase-shifter materials. The XPM testing indicates that this XPM design is able to readily generating sub-100 nm feature in large volume under a much larger and more manageable gap between mask and wafer (20 - 30 micrometers ). 70 nm lines were printed with UV 5 under 25 micrometers mask-to- wafer gap. The simplicity of this design and the intrinsic multiple mask reduction ratio instead of 1:1 for conventional X-ray mask provide an easy analytical tool for this community to study lithographic performance in 50-to-70 nm region.

An array of individually addressable micro-shutters is being designed for spectroscopic applications. Details of the design are presented in a companion paper. The mechanical design of a single shutter element has been completed. This design consists of a shutter blade suspended on a torsion beam manufactured out of single crystal silicon membranes. During operation the shutter blade will be rotated by 90 degrees out of the array plane. Thus, the stability and durability of the beams are crucial for the reliability of the devices. Structures were fabricated using focused ion beam milling in a FEI 620 dual beam machine, and subsequent testing was completed using the same platform. This allowed for short turn around times. We performed torsion and bending experiments to determine key characteristics of the membrane material. Results of measurements on prototype shutters were compared with the predictions of the numerical models. The data from these focused studies were used in conjunction with experiments and numerical models of shutter prototypes to optimize the design. In this work, we present the results of the material studies, and assess the mechanical performance of the resulting design.

Using the MEMSPEC-2000^TM prototype test station, several micromachined structures have been characterized. The MEMSPEC-2000^TM test station employs a laser based non- contact measurement technique to determine the 3D profile of the test structure. Vertical resolution of 0.1 micron and lateral resolution of approximately 1 micron can be achieved. The bandwidth of the sensor is DC to 100 kHz, allowing for time domain measurements of moving structures to be made. Standard static surface profiles have been measured for a number of varied types of test structures. The results of these measurements will be compared with design values. The time response of activated test structures will also be presented and compared to the theoretical predictions based upon modeling equations.

Based on the photographic chemistry, chemically hardening method was selected to enhance the anti-etch capability of gelatin. With the consideration of hardener and permeating processing, formaldehyde is the most ideal option due to the smallest molecule size and covalent cross-link with gelatin. After hardened in formaldehyde, the resistance of the gelatin was obtained by etched in 1% HF solution. The result showed that anti-etch capability of the gelatin layer increased with tanning time, but the increasing rate reduced gradually and tended to saturation. Based on the experimental results, dissolving-flaking hypothesis for chemically hardening gelatin was presented. Sol-gel coatings were etched with 1% HF solution. Compared with the etching rate of gelatin layer, it showed that gelatin could be used as resist to fabricate optical elements in sol-gel coating. With the cleaving-etch method and hardening of dichromated gelatin (DCG), DCG was used as a photoresist for fabricating sol-gel optical elements. As an application, a sol-gel random phase plate was fabricated.

Despite the fact that a number of technical devices, such as piezoresistive sensors or Hall sensors, rely on anisotropic conductivity phenomena, the techniques for modeling anisotropy of conduction are still limited. Usually, those devices are simulated using very specific solutions which are not easily shared between different applications. We have developed a general method for consistent Finite Element Analysis (FEA) modeling based on the diagonalization of the resistivity matrix by main axis transformation. The new method has been successfully applied to simulate piezoresistive four-terminal-transducers such as those used in pressure sensors. In this particular case, the results obtained from the simulation of the mechanical system can be applied to the subnet of the transducer region in a second load step to calculate the electric field distribution. For each finite element, an orthotropic resistivity matrix and the appropriate coordinate system are obtained by diagonalization of the anisotropic matrix, which is calculated from the mechanical stress distribution using the piezoresistive equations. Our new method does not rely on simplifying assumptions concerning the boundary conditions, nor does it neglect parts of the mechanical stress tensors. Based on comparison with theoretical solutions for simple structures and on experimental investigation, matrix diagonalization was found to be a powerful tool for solving problems related to anisotropic conductivity using standard FEA packages.

Low-cost and simple fabrication processes of masks for deep x-ray lithography are necessary for rapid prototyping of high-aspect-ratio microstructures by LIGA-like processes. Commercially available 4' diameter boron carbide substrates of 370 micrometers thickness were investigated as candidates for x-ray transparent mask blanks. High aspect ratio absorber structures were formed by gold electroplating after a x-ray lithographic step using an intermediate Kapton^TM mask. The characteristics for boron carbide masks in terms of x- ray transparency and mask contrast were assessed by simulating exposures into polymethyl methacrylate (PMMA) resist using the wavelength shifter at CAMD and compared to other materials combinations, in particular silicon and graphite-based mask blanks. The boron carbide-based masks proved easy to fabricate and were replicated into 300/500 micrometers PMMA resist at intermediate x-ray energies (5 - 15 keV) on a bending magnet beamline of the CAMD ring operating at 1.5 GeV electron energy. These masks were designed for exposure at high photon energy into very thick resist or stacked exposures and will be tested using the CAMD superconductive wavelength shifter as a source of hard x- rays and associated new high energy x-ray lithography station, when available for use.