With advances in micromachining and the consequent growing sophistication of microstructures, emphasis is increasingly being laid on the design and realization of complete microsystems. In this paper we show some possible combinations of micromachining technologies to build microsystems for applications in photonics, nanoscience, bio-electrochemical systems and micromechanics. The common point of such a large range of devices is their fabrication technology, which has developed from the basic integrated circuit techniques into a wide spectrum of specific micromachining technologies. This article gives an overview of established and newer microfabrication technologies and their application to the construction of some chosen microsystems.

The SAMPLE (Sandia Agile MEMS prototyping, layout tools, and education) service makes Sandia's state-of-the-art surface- micromachining technology, known as SUMMiT, available to U.S. industry for the first time. The Sandia ultra-planar multi- level MEMS technology (SUMMiT) offered through SAMPLE is the world's most advanced surface-micromachining technology, with three independently patternable ultra-low-stress mechanical polysilicon levels (in addition to the electrical polysilicon layer), one-micron design rules, flanged hubs, and CMP planarization of the third sacrificial oxide to provide planar structures in the third mechanical polysilicon layer (MMPoly3). Participants in the SAMPLE program learn about MEMS and SUMMiT process through the Sandia MEMS short course and then use Sandia's specialized design and layout tools to design their own micromachines to be fabricated in SUMMiT.

A novel process for the fabrication of high aspect-ratio high density through-wafer conductive vias is presented. This IC compatible post-processing technology is based on the use of silicon fast anisotropic plasma etching. It overcomes the inherent size or process limitations of previously known methods based on anisotropic chemical etching or laser drilling. The simple process (4 photolithographic steps) includes: (1) Realization of through-wafer holes by fast silicon etching in a low temperature inductively coupled plasma. (2) Insulation of the through-hole walls by room temperature chemical vapor deposition of an organic polymer. (3) Metallization of the through-hole walls by sputtering and evaporation. (4) Insulator dry etching and metal wet etching with a dry film photoresist mask that provides the necessary tenting capability over the through-holes. The process feasibility has been successfully demonstrated with a test design integrated on 100 mm 380 micrometer thick silicon wafers. The through-wafer vias, with a pitch of 350 micrometer and an average density of 100 (DOT) cm^-2, have an electrical resistance of 2 (Omega) and a parasitic capacitance lower than 1 pF.

New techniques for 3D micromachining by direct laser ablation of materials using excimer lasers have been developed. Basic to all of these techniques is the use of image projection in which the laser is used to illuminate an appropriate pattern on a chrome-on-quartz mask. The mask is then imaged by a high- resolution lens onto the sample. Non-repeating patterns with areas of up to 150 multiplied by 150 mm can be machined with sub-micron resolution and total accuracies of the order of a few microns by using synchronized scanning of the mask and workpiece. A combination of synchronized mask scanning and mask dragging techniques (in which the mask is held stationary and the workpiece moved during laser firing) enables patterns of up to 400 multiplied by 400 mm to be produced; the limiting feature being the travel and accuracy of the recision air- bearing stages used to support the workpiece. This talk describes the synchronized mask scanning and mask dragging techniques and illustrates their application by presenting details of novel micromachined structures and devices so produced. These include rapid prototyping of bioprocessor chips, fabrication of mechanical anti-reflection structures in CsI infra-red optical material, patterning films as frequency selective reflecting structures, laser-LIGA and high aspect ratio machining using lamination techniques to produce an optical methane detector.

The removal processes of Si₃N₄- and SiC-ceramics and tungstencarbide were investigated using 40 ps and 10 ns laser pulses. The threshold fluence for removal and the removal rate per pulse were determined. Changes in the chemical composition of the processed surfaces are described and the influence of the removal strategy on the processing results are discussed. Micro-structures were produced in combination with high- resolution optics and precision motion control systems. In SiC-ceramics grooves were produced with geometries smaller than 30 micrometer. In Si₃N₄-ceramics holes were drilled with diameters smaller than 6 micrometer. The influence of scanning velocity, overlap of the laser pulses and pulse energy on material removal and surface finish were discussed.

Advanced silicon micro sensors for pressure, acceleration, angular rate, infrared radiation and atomic force have been developed based on bulk silicon micromachining. Distortion- free, precise or very small micro-nanostructures enables extremely sensitive and quick response sensors. Packaged, capacitive and integrated sensors were fabricated. Electrostatic force balancing sensors and resonant sensors performed wide dynamic range and high sensitivity respectively. Novel micromachining techniques developed and applied for the sensors were vacuum packaging, distortion-free anodic bonding, deep RIE, XeF₂ silicon etching, thickness monitoring during silicon etching, silicon nano-wire growth by electric field evaporation using UHV STM etc.

Small, low cost microphones with high sensitivity at frequencies greater than 20 KHz are desired for applications such as ultrasonic imaging and communication links. To minimize stray capacitance between the microphone and its amplifier circuit, process compatibility between the microphone and on-chip circuitry is also desired to facilitate integration. In this work, we have demonstrated micromachined microphones packaged with hybrid JFET amplifier circuitry with frequency response extending to 100 KHz, and voltage sensitivity of approximately 2.0 mV/Pa from 100 Hz to 10 KHz, and 16.5 mV/Pa at 30 KHz with a bias voltage of 8.0 V. The microphones are fabricated with membranes and fixed backplates made of low temperature plasma-enhanced chemical vapor deposited (PECVD) silicon nitride. Because the maximum temperature of the fabrication process is 300 degrees Celsius, microphones may be built on silicon wafers from any commercial CMOS foundry without affecting transistor characteristics, allowing integration with sophisticated amplifier circuitry. Low stress silicon nitride deposition was used to produce membranes up to 2.0 mm diameter and 0.5 micrometer thickness with plus or minus 0.10 micrometer flatness. The excellent planarity of both the diaphragm and the backplate, combined with a narrow sense gap (approximately 2 micrometers) results in high output capacitance (up to 6.0 pF). The high output capacitance results in noise spectral density which is approximately 3x lower than silicon diaphragms microphones previously fabricated by the authors. Diaphragms with corrugations were fabricated to relive tensile stress, to increase deflection per unit pressure and to increase deflection linearity with pressure.

An array of electrochemical sensors -- amperometric detection -- was developed using silicon planar technology. Our main purpose is to detect the activity of free radicals such as nitric oxide (NO) at cellular dimensions. In this paper we focused on the process sequence used to produce silicon microprobes, based on plasma etching. Typical dimensions of the structures are: a length of 10 mm, a width of 1 mm, a tip width of 60 micrometers, and a thickness of 30 micrometers. Four different probe designs were adopted in order to test mechanical integrity. The defined process using plasma etching revealed to be feasible, although the lateral walls of the obtained probes resulted very rough. Preliminary mechanical tests were performed using probes with a thickness of 300 micrometers. Probes with wider shapes seem to have a better combination of higher fracture force and possibility to place more electrodes close to the tip.

We have observed the etch rate and the underetch rate of <100>-, <110>-, and <111>- oriented silicon substrates in isotropic etching solutions. We have studied the influence of the composition of the solution and the temperature on the etch rates. Further we also have examined the stability of different masking materials. The stability of thermally grown SiO₂ is very poor. Silicon nitride films show a comfortable stability at low etching temperatures. The stability of these films decreases with significant differences depending on the deposition temperature. The best stability were found with metal masks and photoresist masks. The values of the etch rates were in a range between 1 micrometer/min and about 900 micrometers/min. A controlled procedure could be achievable up to etch rates of about 100 micrometers/min. The etch rates and the undercut rates as well as the etch rates of the differently oriented materials are different under the same process conditions. In some cases we found profiles that are known from anisotropic dry etching procedures. All achieved results indicate an anisotropic etching behavior of silicon in etchants based on compositions of HNO₃-HF-H₂O.

Composite electroforming is an electroplating technique basically. The ceramic or other type powder is mixed into electroforming solution, then codeposited with metal ion by using electroplating method. The codeposit is strengthen by the ceramic powder, which can be used for the application in MEMS field. We do the microcomposite electroforming research by using ultrafine (submicron or nano-sized) powder. The 20g/L silicon carbide powder added to nickel sulfamate electroforming solution can obtain the higher hardness and internal stress deposits (1.5 wt% SiC). Because high internal stress is harmful for electroforming process, it's necessary to take a suitable electrolyte and controlled condition for high hardness and low internal stress in microcomposite electroforming process.

Economic success of microsystems technology requires cost- effective fabrication in large series as well as a great diversity of materials processing technologies. The different techniques of micro molding meet all these requirements. An important economic factor is the reduction of cycle time by process and tool optimization with simulation techniques. Actually, minimal cycle times are about two minutes in certain cases. Evolution of thermoplastics processing technologies is demonstrated by application of technical or even high- performance polymers like PEEK, PMMA or PSU. For manufacturing of metal microstructures, we develop three possibilities: microstructures like stepped LIGA gear wheels are obtained from galvanization on lost molds, which have been injection molded using conductively filled polymers. Additionally, electroless plating is used to replicate nonconducting plastic microstructures and the metal injection molding (MIM) process is under development. A quite different approach uses polymer precursors containing monomer/polymer mixtures in reaction injection molding. We chose photoinduced polymerization without any preheating step using photopolymerizable resins. Avoiding the time consuming thermal cycle, molding takes place at ambient temperature. Due to the low viscosity, the microcavities should be filled completely. The process is characterized by the integration of a powerful UV-source and a partially glass made molding tool.

Nickel structures were electroformed from a commercially available nickel sulfamate bath. The plating molds were made of thick photoresist (approximately 20 micrometers) and delineated by a UV lithographic method. For mold cavities with very small aspect ratios (minimum planar dimension/mold thickness), the deposition rate is higher for those with smaller feature sizes than those with larger feature sizes. For mold cavities with large aspect ratios, no such correlation was observed. X-ray and transmission electron microscopy results show that the electroformed nickel is polycrystalline and in columnar form. For current density less than or equal to 8 mA/cm², the nickel deposits orient preferably with <220> crystallographic direction normal to the substrate surface. For current density greater than or equal to 12 mA/cm+2), the nickel cantilevers tend to curl downward, and the nickel deposits orient preferably with <200> crystallographic direction normal to the substrate surface. There are only minor differences in the relative intensities of the (111), (200) and (220) x-ray peaks of the nickel deposits electroplated on gold, copper and chromium, implying that the effect of the plating base material on the nickel structure is minimal. The relative intensities of the (111), (200) and (220) x-ray peaks vary throughout the thickness of nickel structures. However, the variations are random, and therefore no correlation between the crystallinity and the built-in stress can be established at this point.

High aspect ratio line and trench plating molds suitable for microactuator applications were etched in polymer using oxygen plasma in an rf inductive plasma etcher. A high vertical etch rate of approximately equals 2.5 micrometer/min in a polymer has been achieved for 2 micrometer wide lines and trenches, with even higher rates being observed for wider trenches due to the usual RIE lag effect. The lateral etch rate can be reduced by adjusting the inductive to bias power ratio, and by lowering the etch temperatures. Under optimum etching conditions, aspect ratios of close to 20:1 in a 2.5 micrometer line/2.0 micrometer spacing pattern and of greater than 20:1 in isolated 2.0 micrometer lines with greater than or equal to 5 micrometer spacing have been achieved.

To implement optical submodules or systems of the future we have identified a few key components and technologies necessary to build optical products at Hewlett Packard. To be competitive these optical assemblies must be smaller, cheaper and more functional, then current optical products while maintaining or exceeding the existing performance level. To accomplish this task we introduce the idea of a silicon micro- optical bench (SMOB). The focus of the micro-optical bench has been laser submounts and collimators. However, while making advances in these platform technologies, the importance of micro parts which can be used to augment and expand the optical functions has become apparent. In this paper the role of silicon as a micro-optical bench substrate is described along with implementations of micro-optical benches. Silicon is an excellent choice as a base platform for SMOB technology because of its availability and excellent material properties and advanced processing technology. Structures to aid in batch assembly processes are easily constructed from silicon wafers. We show how to create structures which allow placement of ball lenses and other three dimensional structures to 1 micrometer accuracy. This can be accomplished in a batch process with the potential for reductions in cost of assembly. We have built generic laser submounts and collimators with various sizes of ball lenses. We show how the performance of these submounts agrees with the theoretical predictions. For fiber to ball coupling Gaussian methods work well. However, for laser to fiber coupling via ball lenses it is necessary to use a Maxwell equation solver in spherical coordinates to correctly predict the spherical aberration effects. The ball lenses can collect the laser light with great efficiency at a fraction of the cost for convectional GRIN or aspheric lenses. Furthermore, the small size allows the whole optical part to fit within standard hermetic packages.

Thick polysilicon layers (greater than 10 micrometer), grown in an epitaxial reactor, are highly desirable for surface micromachining applications. The mechanical properties of these layers were studied extensively by characterizing the stress and stress gradient. The stress profile and texture were insensitive to variations of deposition parameters both of the polysilicon seed layer and the epitaxial process, and were influenced to a small degree by doping with phosphorous. Annealing in oxygen ambient resulted in compressive stresses up to 80 MPa and stress gradients of -10 MPa/micrometer. Subsequent annealing in nitrogen reduced the stress and stress gradient, but it can be reversed by re-annealing in oxygen. A model based on diffusion of oxygen is presented explaining the influence of the annealing on stress. Oxygen atoms diffuse into polysilicon during an anneal in the oxygen ambient, introducing compressive stress. Upon annealing in the nitrogen ambient, oxygen is released from the polysilicon layers due to the partial pressure of oxygen at the annealing temperature. The diffusion of oxygen atoms out of the layers results in a partial reversal of the mechanical effects. This insight gives the possibility to tailor the stress of thick polysilicon layers within certain limits to the specific needs of the application.

Optical interferometry has been applied to determine the membrane curvature of p⁺⁺Si beams. Clamped-clamped Si beams and cantilevered beams were fabricated with an etch- diffusion process and a dissolved wafer process and characterized. This measurement technique allows for very precise measurement of the bending of released Si beams due to stress, thus small height variations due to membrane curvature in clamped-clamped beams can be resolved. Cantilevered beams were found to bend more due to stress as length increased and width decreased. Thicker beams also showed less bending due to stresses due to their increased stiffness. A 6.0 micrometer thick cantilevered beam had a deflection of 12.4 micrometer due to stress, while a 36.7 micrometer thick beam had a deflection of only 0.2 micrometer. Beams fabricated using a dissolved wafer process with a 12 h B diffusion were found to bend the same amount as those fabricated using an etch- diffusion process with a 4 h diffusion. Using the deep etch- shallow diffusion process, resonating elements that are 20 micrometer long, 4 micrometer wide, and 28 micrometer thick were found to be perfectly flat without any bending.

High stress levels can cause problems for both electronics and micromechanics. It is therefore important to characterize the stress and strain of the different mechanical layers used for processing. In order to predict the properties of a multilayered structure it is not sufficient to know the mechanical properties of each independent layer. The deposited layers may have a considerable effect on the mechanical properties of the underlying layer. This paper discusses the importance of the effect of each layer on underlying layers and on the total structure, using poly-silicon and silicon- nitride as the mechanical layers. The measurements show that at an anneal of 850 degrees Celsius the influence of nitride on the underlying poly is considerable. At an anneal of 1000 degrees Celsius this effect disappears. We also examined the stress in poly-nitride-poly layers in order to find out the influence of annealing in between the deposition of the layers. Measurements show that the temperature of the anneal is the dominant factor.

Shape memory alloy (SMA) materials have a number of desirable properties which make them strong candidates for microactuator applications. Compared with other means of microactuation based on piezoelectric, electrostatic or bimetallic principles, SMA microactuators have advantages which include high maximum work energy density, high power/mass ratio and the capability of being driven without high applied electric fields. Consequently, other desirable features such as biocompatibility and scalability to small dimensions can also be exploited. In this paper we report on the production of TiNi shape memory films by ion sputter deposition onto unheated substrates using argon ions generated by a Kaufman- type source. The films were characterized by electrical resistivity measurements and by x-ray reflectometry. R-phase and martensitic transformations are seen without high temperature annealing and the shape memory properties observed are compared with those of films prepared by dc and rf magnetron sputtering.

Patterning of thin films or foils by wet etching generally involves selective material removal through photoresist masks. Compared to the commonly employed chemical etching process, the electrochemical method of metal removal offers better control and flexibility for microfabrication. Other advantages include higher machining rate, the use of non-toxic and non- corrosive electrolyte and the possibility of machining a wide range of electrically conducting materials. Electrochemical metal removal (electrochemical micromachining) is now receiving attention in the electronics and other high-tech industries as a greener processing technology for microfabrication. Several examples of the application of electrochemical micromachining are presented in this paper. These examples demonstrate the challenges and opportunities offered by electrochemical metal removal in microfabrication.

A novel singled-sided multilevel island-beam-diaphragm structure has been designed and fabricated for an extremely high sensitivity pressure transducers by using a novel anisotropic etching technology called masked-maskless anisotropic etching technology. The structure consists of two small islands for overrange protection, two shallow masses for stress concentration, three thin beams on a deep-etched thin diaphragm for piezoresistors location. A prototype pressure transducer of 400 pa operation range and 0.6% nonlinearity has been tested.

This paper presents a new technique of micromachining using macro porous silicon. Macro porous silicon is made by electrochemical etching in hydrofluoric acid. The etch rate and the morphology of the etched surface as a function of etch parameters, (current density, applied voltage and HF concentration) are investigated. Optimization of these parameters makes it possible to fabricate a micromechanical structures such as 45 micrometer deep, 3 micrometer wide and 8 micrometer pitch trenches. Furthermore the diameter of the pore is easy to control by adjusting the current density. During the pore formation an increase in the current density leads to an increase in the pore diameter. This does not effect the diameter of existing pores. This connection of the pores under the structure can be achieved. In this way, various kinds of single crystal silicon micromachined structures can be fabricated.

We have developed a focused ion beam (FIB) system for automated MEMS processing. This product, the Micrion MicroMill, has been successfully used in production and prototype milling of over three million thin film heads (TFH) used in hard disk drives. The FIB column consists of a liquid gallium (Ga⁺) ion source, running at 50 kV, producing beam currents up to 50 nA. The milling rates achieved in the TFH application have been 0.5 - 4 micrometer³/sec with spot sizes ranging from 150 - 800 nm. This tool is designed to easily integrate into current FAB facilities and supports a wide range of navigational requirements. Different milling scenarios can be easily created or modified using the integrate CAD-like design tools, allowing for quick production line design modifications or rapid prototyping of new designs. The milling strategy can 'adapt' to dimensional changes caused by upstream process variations. On a real-time basis, the FIB system's pattern recognition/inspection software measures the individual part and precisely places the desired milling pattern. The flexible vector scan beam control can position the FIB, within sub-tenth micron dimensional control, to generate an endless variety of geometric milling patterns. This presentation will discuss the work currently done on inductive and magnetoresistive TFH devices as well as other potential MEMS processing applications.

The aim of this paper is to determine an optimum nonselective etching solution in order to manufacture an as thin as possible, uniform and high quality GaAs membrane. Three different etching systems in various proportions of the components were analyzed. A high quality 10 micrometer thin GaAs membrane was obtained using the [1(H₃PO₄)]: [1(CH₃OH)]: [3(H₂O₂)] etching solution. The micromachined GaAs membranes are manufactured to be used as support for microwave circuits as well as in high temperature sensor applications.

High volume silicon micromachining has been employed by the automotive industry for 20 years. This paper examines past, current and future applications of MEMS to the automobile. Both sensor and the application of micromachining to other automotive areas are covered. Technologies such as wet and plasma etching, wafer bonding, LIGA, circuit integration and packaging are discussed.

The assembly of hybrid micro systems is usually done by hand with the help of tweezers and optical microscopes. It is obvious, however, that only the automation will lead to an efficient and precise assembly process. This paper describes the design, the function and the application of mechanical grippers for automated micro assembly. These grippers are powered by piezo systems and are able to move their arms in sub-micrometer steps in order to grip micro parts very precisely. They can be equipped with sensors for the detection of gripping force and have been designed especially for use in a large-chamber scanning electron microscope (LC-SEM). Process observation is a main problem in all aspects of micro technology. The LC-SEM allows on-line process observation with a very high depth of focus and a large lateral resolution. It has a 2 m³ vacuum chamber in which complete assembly units can be installed. Furthermore the electron gun is freely movable, so that a sample can be observed from all directions. An additional advantage of this microscope is the clean production environment (vacuum).

The field of micromechanics is rapidly expanding in both the number of research groups and the number of materials being employed. Although this diversity is a strong indication of a healthy field, care must be taken to keep the focus on producing products and processes which can be transferred to the manufacturing facility. During the 1980s polysilicon was shown to contain a significant amount of process flexibility and economic potential. Although the demonstration of polysilicon sensors was noticed and in some cases pursued by industry, single-crystal silicon sensors continue to dominate the products used by the primary sensor customer, the automotive industry. A similar trend which also began in the 1980s was the use of the LIGA process for sensor fabrication. Once again, this field showed a significant amount of economic promise. However, for the resources being invested and the number of research groups pursuing this process, significant problems exist with respect to product manufacturability. Although LIGA remains an exciting field of research, new micromechanical processes or materials may greatly reduce the window of device profitability before the difficulties associated with LIGA can be brought under control. Oddly enough, it is the same material which polysilicon has failed to displace which may limit the LIGA process to only one application area, that area being magnetics. New deep anisotropic etching systems and new substrate suppliers for micromachining applications, along with the knowledge and experience industry already possesses, will maintain single crystal silicon as the sensor material of choice for the 1990s and beyond. This article reviews the material stability and processes associated with polysilicon, single crystal silicon, and electrodeposits. Emphasis will be placed on the inherent material structure and processes required to manufacture a profitable device.

MEMS is an enabling technology that may provide low-cost devices capable of sensing motion in a reliable and accurate manner. This paper describes work in MEMS accelerometer development at Sandia National Laboratories. This work leverages a process for integrating both the micromechanical structures and microelectronics circuitry of a MEMS accelerometer on the same chip. The design and test results of an integrated MEMS high-g accelerometer will be detailed. Additionally a design for a high-g fuse component (low-G or approximately equals 25 G accelerometer) will be discussed in the paper (where 1 G approximately equals 9.81 m/s). In particular, a design team at Sandia was assembled to develop a new micromachined silicon accelerometer which would be capable of surviving and measuring high-g shocks. Such a sensor is designed to be cheaper and more reliable than currently available sensors. A promising design for a suspended plate mass sensor was developed and the details of that design along with test data will be documented in the paper. Future development in this area at Sandia will focus on implementing accelerometers capable of measuring 200 kilo-g accelerations. Accelerometer development at Sandia will also focus on multi-axis acceleration measurement with integrated microelectronics.

The influences of surface characteristics, including adsorptive states led by different chemical treatments and surface roughness, on direct bonding between dissimilar CVD materials were investigated. The bonding procedures were carried out at temperature lower than 400 degrees Celsius. In this temperature range, LPCVD poly-silicon, PECVD oxide, and LPCVD silicon-nitride showed highly process dependent bonding behaviors, i.e., bondable or not bondable to another material under certain experimental conditions. Based on these facts, a selective bonding conception for Si-based CVD material is proposed and applied to fabricate new fluid structures and devices.

Microsuspensions are very useful mechanical structures in microelectromechanical systems. The fabrication processes of microsuspensions, including front-side etching and back-side etching processes, have been studied extensively. Due to the restriction of undercutting process, the front-side etching approach offers only limited patterns of microsuspension. The present study intends to develop a method to predict the possibility of fabricating microsuspensions on a (100) substrate through front-side etching process. According to the proposed method, microsuspensions with arbitrary shapes can be designed easily. It is found that the formation of the microsuspensions predicted by the proposed technique agrees well with the experimental observation. The contribution of this paper is to provide a convenient tool to design microsuspensions fabricated through front-side etching process. The application of front-side etching process on microsuspensions will become more attractive. Thus the problems of having a large cavity on substrate, longer etching time, and larger die size leaded by the back-side etching process can be prevented.

An experimental study was performed to investigate the effects of high temperature anneal treatments on the microstructure and curling behavior of heavily boron-doped silicon structures. Cantilever structures were created from p++ boron-diffused silicon wafers. The post-diffusion anneal treatment temperature was varied while the anneal time remained constant. The micromechanical cantilevers were analyzed for curl as a function of the anneal temperature using an optical profiler. Bulk sections from the wafers were analyzed to obtain boron concentration, distribution of lattice constant, and dislocation distribution. Results of the curl measurements revealed that all non-annealed cantilever structures were curled in one direction, and those annealed for 90 minutes above 1100 degrees Celsius were all curled in the other direction, with an apparent transition temperature of about 1050 degrees Celsius. Secondary ion mass spectroscopy (SIMS) analysis confirmed that boron concentration becomes more uniform through the wafer thickness with increasing anneal temperature. X-ray diffraction revealed that the magnitude of the smallest lattice constant present in a wafer increases with increasing anneal temperature, which may allow a compressive stress to develop. Transmission electron microscope (TEM) observations showed that dislocations move during the anneal process to relieve stresses.

Statistical process control (SPC) has gained wide acceptance in recent years as an essential tool for yield improvement in the microelectronics industry. In both manufacturing and research and development settings, statistical methods are extremely useful in process control and optimization. Here we describe the recent implementation of SPC in the micromachining fabrication process at Draper. A wide array of micromachined silicon sensors, including gyroscopes, accelerometers, and microphones, are routinely fabricated at Draper, often with rapidly changing designs and processes. In spite of Draper's requirements for rapid turnaround and relatively small, short production runs, SPC has turned out to be a critical component of the product development process. This paper describes the multipronged SPC approach we have developed and tailored to the particular requirements of an R & D micromachining process line. Standard tools such as Pareto charts, histograms, and cause-and-effect diagrams have been deployed to troubleshoot yield and performance problems in the micromachining process, and several examples of their use are described. More rigorous approaches, such as the use of control charts for variables and attributes, have been instituted with considerable success. The software package Cornerstone^R was selected to handle the SPC program at Draper. We describe the highly automated process now in place for monitoring key processes, including diffusion, oxidation, photolithography, and etching. In addition to the process monitoring, gauge capability is applied to critical metrology tools on a regular basis. Applying these tools in the process line has resulted in sharply improved yields and shortened process cycles.

A novel KOH silicon maskless anisotropic etching technology is adopted to fabricate micromachining silicon mass-beam structure accelerometer. Lateral sensitivity effect in normal accelerometer is eliminated because the beams which are thinner than 15 micrometers have been formed in the middle of the seismic mass. Based on the calculation of sensitivity and basic resonance frequency of two kinds of bulk micromachining accelerometers, the structure parameters of cantilever and double-side-supported accelerometer have been optimized by using the sensitivity-frequency product as the figure of merit of a structure. The different etching characteristics of {311} and {100} plane of silicon in KOH maskless anisotropic etching process have been investigated thoroughly and utilized in the fabrication of symmetric mass- beam structure. Special damping design has been proposed to reduce the damping ratio of the device in order to improve the dynamic performance of the accelerometer. Preliminary measurement of the static characteristics of the structure has been performed with a force-deflection balance measurement apparatus.

A simple and effective method using a balance to measure micro force and corresponding deflection is presented. The method is proved to be very practical in testing the force-deflection behavior of silicon cantilever, in which the Young's modulus of the material can be calculated, and in investigating the static performance of bulk micromachined capacitive accelerometers. The balance approach for micro force- displacement measurement is very attractive for its easiness in operation, low cost and higher resolution.

In recent years, microsystem technology and its growing importance for actuators, sensors, optics and microfluidics, only to name a few, have gained a lot of attention. Specific applications demand fabrication techniques allowing a fast and reliable replication of microstructure products in a variety of materials. An important technique for replication processes of microstructures in many applications of microsystem technology are microelectroforming processes, generating a variety of metals and metal alloys with tailored characteristics. Here, new results in the development of alloys for specific applications as well as their applications are reported: (1) Newly developed alloys: Nickel-iron alloys enable the production of soft magnetic microstructures e.g. for specific applications in microactuators. Nickel-cobalt and Nickel-tungsten alloys have been employed for the manufacture of microstructured tools with excellent mechanical properties regarding wear and mechanical durability. These tools have been applied to hot-embossing and injection molding processes successfully. (2) Microelectroforming within the frame of the LIGA technique allows the manufacturing of extremely precise electrodes with various cross-sections and heights for (mu) - electro discharge machining. The combination of these techniques enables the production of microstructures from non- electrodepositable materials, like stainless steel e.g. for large scale replication processes. (3) The precision of microelectroforming enables the replication of structured surfaces on a nanoscale for molecular microelectronics or special applications. The new types of alloys reported here significantly enlarge the applicability of microelectroforming processes for tool fabrication or direct use. Moreover combining this process with other microstructuring processes like injection molding or (mu) -EDM techniques generates a powerful tool for microsystem technology.

The fabrication of components for a microchannel chemical solvent separation unit is described. The performance of this unit is intended to employ enhanced kinetic effects due to short contact times encountered in to facilitate extraction of one dissolved species from one solvent into another. Components for the device are fabricated by laser micromachining, photochemical machining, and photolithographic patterning. The separation unit consists of a series of parallel flow and counterflow microchannels separated by micromachined membranes and assembled into a single unit by a lamination process. In a sample design, channel width, membrane width and length are 100 micrometer, 1 cm, and 8 cm respectively. Test membranes were fabricated from stainless steel using photochemical machining and from polyimide by using two distinct laser micromachining processes. Use of the lamination fabrication method allows flexibility in the design of the microchannels within the unit. Preliminary results of membrane tests and a brief discussion of future efforts are included.

In general liga technology must use the x ray from synchroclotron to radiate the material such as PMMA plane. It cannot utilize in common laboratory and research work in microelements fabrication of micromachining are inconvenient and expensive. Laser liga technology can be convenient to use, it effective developed in SIOFM in China. A pulse excimer laser with 248 nm wavelength and frequency-tetrad Nd:YAG laser with 265 nm wavelength through an optical uniformer and 10:1 projective lithophoton system for imaging the mask on the PMMA surface. Owing to cold ablation effect of UVU laser light, it can precise litho a reduce image with less than 1000 (mu) diameter and a 106 micrometer deep on PMMA surface. From experimental ablation curve which got by us and can choose the optimum condition for processing the microelement. SIOFM also developed a kind of microelement of cantilevel beam of GaAs with 3 micrometer thin. To radiate it with modulated semiconductor laser. A sinuous vibration with amplitude in order of micrometer and 10⁵Hz frequency has been found. It can be used in modulating the micro-light beam and in multicanal fiber communication.