Proceedings Volume 2882

Micromachined Devices and Components II

Kevin H. Chau, Ray M. Roop
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Proceedings Volume 2882

Micromachined Devices and Components II

Kevin H. Chau, Ray M. Roop
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 17 September 1996
Contents: 10 Sessions, 34 Papers, 0 Presentations
Conference: Micromachining and Microfabrication '96 1996
Volume Number: 2882

Table of Contents

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Table of Contents

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  • Integrated Microdevices and Microsystems
  • Chemical Sensors
  • Infrared Sensors
  • Accelerometers and Gyroscopes
  • Modeling
  • Actuators
  • Flow and Magnetic Sensor
  • Pressure and Strain Sensors
  • Poster Session
  • Plenary Papers
Integrated Microdevices and Microsystems
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New developments in the integration of micromachined sensors
Pasqualina M. Sarro, Patrick J. French, Paul T. J. Gennissen
Micromachining technologies, thin film deposition and bonding technology, along with continued advances in silicon semiconductor circuitry, have resulted in miniature sensing devices whose performance is equal to and sometimes better than their full-sized counterpart. However, despite the obvious benefits and needs for microsystems solutions, the production and marketing thereof have proved to be more difficult than anticipated. The advantages related to the use of conventional IC processes to fabricate the various components of a microsystems have been often acknowledged. The problems resulting from the constrains of IC compatibility requirements have been extensively discussed. New upcoming silicon micromachining technologies and some interesting developments in the existing ones, seem to help meet these requirements. In this paper, some very promising techniques, such as epi-micromachining, laser micromachining, deep reactive ion etching of silicon and low temperature Si to Si bonding are reviewed. Examples of integrated micromachined sensors and devices which benefit from these new developments will be presented to underline the promise and expectation of these technologies. Further, developments made in CAD systems for microelectromechanical systems and the availability of MEMS technology in a multi- user environment are mentioned as they can have a positive impact on the integration of micromachined sensors.
Compatible CMOS microsystems for automotive and medical applications
Ralf Kersjes, W. Mokwa
Integration of sensors and electronics on the same substrates becomes more and more important. CMOS circuit design seems to be the most important technique for the monolithic approach. Compared to bipolar circuits power consumption is much lower, compared to BICMOS the process is much less complex therefore having a much lower number of masks. This is very important because inmost cases monolithic integration means additional process steps and by this a higher process complexity. This paper wants to give a few examples for the monolithic approach in the field of physical sensors based on CMOS-technologies for automotive and for medical applications.
Stacked multichip-module technology for high-performance intelligent transducers
Siebe Bouwstra
The development of a technology platform for advanced modular integration of integrated circuits and micromechanical transducers in space constrained applications is presented. This includes the development of a technology for vertical feedtroughs based on the use of electrodepositable photoresist, and the development of a technology for interconnecting transducer chips and circuit chips using eutectic solder bump bonding. Different topologies are considered.
Thermopneumatical micropump and microvalves for a medical analyzing system
Zouhair Sbiaa, Henri Camon, Daniel Esteve
The chemical analysis plays an important role in a clinical medicine. A small size of the analyzing system and reduced sample volume are required. Fully recognizing the benefits of this technology, we are working in the frame of a European project called BARMINT (basic research for microsystem integration) and is concerned with the development of a novel microsystem containing chemical and pressure sensors for the chemical analysis of fluids.
Applications of bipolar compatible epitaxial polysilicon
Paul T. J. Gennissen, Patrick J. French
In surface micromachining applications thick polysilicon layers are highly desirable. The low deposition rate of LPCVD poly-silicon severely limits the final thickness of the microstructures. This can be overcome by using an epitaxial reactor to grow polysilicon, in which very high deposition rates can be obtained. However, when a complete electronic process is used to fabricate smart sensors, the epipoly will be under compressive strain. The cause of this unwanted strain has been identified and the problem is solved by capping the epipoly with a nitride layer during further processing. In this way thick low-stress epipoly layers grown at the same time as the monocrystalline silicon epilayer required for the electronics, have been obtained. Several test structures, such as thermally actuated indicators, lateral accelerometers and lateral comb drives have been fabricated using this optimized process.
Chemical Sensors
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Silicon integrated microsensor incorporating a metal-doped phthalocyanine organic semiconductor used to selectively detect nitrogen dioxide and an organophosphorus compound
Edward S. Kolesar Jr., John M. Wiseman
A novel gas-sensitive microsensor, whose design is based upon the interdigitated-gate-electrode field-effect transistor was realized by integrating it with ia selectively-deposited, chemically-active, electron-beam evaporated copper phthalocyanine (CuPc) thin film. When isothermally operated at 150 degrees C, the microsensor can selectively and reversibly detect parts-per-billion (ppb) concentration levels of two environmentally-sensitive pollutants, nitrogen dioxide (NO2) and diisopropyl methylphosphonate (DIMP). Although the CuPc thin film chemically and electrically interacts with NO2 and DIMP, just as it will likely interact with other electrically- active gases, or combinations thereof, the selectivity feature of the microsensor was established by operating it with a 5-V peak amplitude, 2-microsecond(s) duration, 1000 Hz repetition frequency pulse, and then analyzing its time- and frequency-domain responses. As a direct consequence of this analysis, the envelopes associated with the normalized- difference Fourier transform magnitude frequency spectra reveal features which unambiguously distinguish the NO2 and DIMP challenge gas responses. Furthermore, the area beneath each response envelope may correspondingly be interpreted as a metric for the microsensor's sensitivity to a specific challenge gas concentration. Scanning electron microscopy was used to characterize the CuPc thin film's morphology. Additionally, infrared spectroscopy was employed to verify the (alpha) - and (beta) -phases of the sublimed CuPc thin films and to study the NO2- and DIMP-CuPc interactions.
Deflection behavior of Fabry-Perot pressure sensors having planar and corrugated membrane
Jaeheon Han, Dean P. Neikirk
Micromachined Fabry-Perot microcavity structures have been investigated for use as pressure sensors. For the application of pressure sensors, the devices are categorized based on the shape and location of the deflecting diaphragm. Discussed here are planar bottom, planar top, and corrugated top diaphragm Fabry-Perot microcavity structures. Output signal degradation as a function of pressure, referred to as the signal averaging effect, caused by the non-planar deflection of an edge-clamped diaphragm, is reduced using planar top diaphragm structures, as compared to planar bottom diaphragm structures. This is achieved by improving the flatness of the deflecting diaphragm in the optically sampled area of the planar top diaphragm structures by adjusting the ratio of the top diaphragm area to the bottom diaphragm area. Corrugation of the top diaphragm structure further enhances flat deflection. However, the corrugated structures induce a static deflection of the diaphragm due to localized internal stress generated by the asymmetry of the corrugation on the diaphragm, referred to as the zero- pressure offset effect. The existence and influence of these parasitic effects have been observed using real-time measurements of the diaphragm deflection.
Technologies and microstructures for separation techniques in chemical analysis
Vincent L. Spiering, Theo S. J. Lammerink, Henri V. Jansen, et al.
The possibilities for microtechnology in chemical analysis and separation techniques are discussed. The combination of the materials and the dimensions of structures can limit the sample and waste volumes on the one hand, but also increases the performance of the chemical systems. Especially in high performance chromatography separation systems, where the separation quality is directly depending on the length to width ratio of the fluid channels, there is a large potential for applications. Novel technologies as well as demonstrator devices for different applications will be presented in this paper. Finally, a modular concept for microfluidic systems, in which these micromachined structures can be incorporated, is described and illustrated with a demonstrator.
Infrared Sensors
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Antenna-coupled rectifying diode for IR detection
Hideaki Yamagishi, Hitoshi Hara, Nobuhiko Kanbara, et al.
An antenna-coupled rectifying SChottky Barrier DIode (SBD) for IR detection is fabricated on Si by IC processes. Aluminum thin film antenna of 30 micrometers length and 1.5 micrometers width is formed on thermally grown SiO2 layer on Si. At the end of antenna, rectifying SBD of 0.03 micrometers diameter is formed by focused ion beam (FIB) milling technique. Ion current monitoring system with FIB largely reduced the size of milled hole, which is conventionally limited by ion beam waist diameter. IR radiation from CO2 laser of 10.6 micrometers in wavelength and 0.55 W in power is used for device evaluations. Signal dependence on incident angle of CO2 laser radiation and dependence on diode bias voltage are evaluated. We confirmed the rectifying operation of antenna- coupled SBD at IR region and experimentally obtained rectified voltage of 173 nV. The NEP is calculated to be 1.94 X 10-6 W/Hz-1/2.
Micromachined VO2-based uncooled IR bolometric detector arrays with integrated CMOS readout electronics
Hubert Jerominek, Martin Renaud, Nicholas R. Swart, et al.
Uncooled IR bolometric detectors fabricated using surface silicon micromachining are presented. The detector fabrication process employs a polyamide sacrificial layer, and a VO2 thermistor layer exhibiting a thermal coefficient of resistance on the order of -3 percent/degrees C. Detector sizes are 100 micrometers X 100 micrometers and 50 micrometers X 50 micrometers , and 64 X 64 and 128 X 128 pixel arrays are fabricate. The detectors exhibit responsivities of up to 15 000 VW-1, normalized detectivities typically exceeding 108 cm Hz1/2W-1, and response times below 20 ms. Three integrated readout circuit designs for 64 X 64 and 128 X 128 pixel detector arrays, fabricated using a standard 1.5 micrometers CMOS process,a re described. These circuits include several test and detector nonuniformity correction features and can operate in either self scanning mode at a rate of 30 frames per second, or in the random access mode in which column and row addresses are input directly.
Optimization of CMOS infrared detector microsystems
Niklaus Schneeberger, Oliver Paul, Henry Baltes
We report the fabrication and characterization of nine different infrared detector microsystems produced with two different commercial CMOS processes. They consist of micromachined thermoelectric sensors with on-chip signal conditioning circuitry. We developed a model for the performance of such microsystems based on numerical finite element analysis of the sensor and performance figures of the circuitry. The model was validated by comparing calculated and experimental sensor outputs. Deviations between modeled and measured performance were smaller than 21 percent. The usefulness of the model to optimize the layout of thermoelectric infrared sensors wit respect to overall system performance is demonstrated.
Accelerometers and Gyroscopes
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Silicon accelerometers: generic design and operating principles and a case study
The generic design and operating principles of acceleration sensors are reviewed in terms of three partial transfer functions. An accelerometer's mechanical transfer function describes the conversion of an applied acceleration input into mechanical stress and strain in structural elements. Its electromechanical transfer function describes transduction of these elementary quantities of the mechanical energy domain into elementary quantities of the electrical domain. The electrical transfer function describes conversion of the elementary electrical quantities into an electrical output signal. The generic design issues and principles are highlighted for each of the partial transfer functions, within the boundary conditions of silicon implementations and against the widely varying background of diverse application areas. The case study of a bulk micromachined uniaxial capacitive micro-accelerometer illustrates a reduction to practice and demonstrates how accelerometer performance specifications are translated into silicon, based on the generic design principles.
Stress-induced warpage and the compensation in a composite micro-accelerometer
Gary X. Li, Ron J. Gutteridge, Dan N. Koury, et al.
Mechanical modeling and analysis have been carried out for a fabricated micro-accelerometer. The sensor is designed with composite polysilicon/silicon nitride tether arms to provide a net overall tensile state. The stress distribution in both polysilicon and silicon nitride films, and the resulting structural deformation, have been calculated. Both experimental results and finite element analysis (FEA) of the complete sensor structure show that a consistent upward deflection of the tether structure exists, which causes an off-set of the suspended poly plate and results in yield loss and sensor performance degradation. This phenomenon is explained by designing, fabricating, and testing two cantilever beams with cross-sections similar to the actual tether structure. Depending on the beam's cross-section dimensions, all the cantilever samples also exhibit upward deflection to varying degrees. Theoretical analysis and FEA simulation are conducted for the cantilever beams, and the results compared with experimental data. An analytical formula is provided to optimize the composite polysilicon/silicon-nitride tether geometry to minimize or eliminate the undesirable stress-induced deflection.
Micromachined vibrating gyroscopes
Jan Soderkvist
Angular rate sensors are often used in combination with accelerometers. Both sensor types are based on inertial forces and they do not require direct contact with the surrounding. However, angular rate sensors are much more difficult to design and fabricate due to them using large ratios of vibration amplitudes which makes them very sensitive to various error sources. This is one reason why micromachined rate sensors ar not frequently found on the market, despite a large interest from the automotive and military industry. Nevertheless, vibrating angular rate sensors have a large potential for such applications. A general description of vibrating angular rate sensors and some design aspects is given below, together with a more detailed description of a quartz angular rate sensor. This quartz sensor is currently developed for mass-production in collaboration with a major European automotive industry.
Micromachined rotating yaw-rate sensor
Robert B. Yates, Connel B. Williams, Chris Shearwood, et al.
This paper describes a novel, electromagnetically levitated, micromachined gyroscope or yaw rate sensor. The device uses a rotor spun at high speed and has the potential for several orders of magnitude improvement in yaw rate sensitivity when compared to other micromachined sensors. The first prototype rotates at just over 1,000 revolutions per minute, with a predicted sensitivity of approximately 0.5 degrees per second. The model indicates that this rotation speed may be increased by orders of magnitude, with corresponding increases in the sensitivity, as the speed of rotation is only limited by the drag force in air. The device also has the advantage that it is extremely simple to fabricate.
Modeling
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Microsystem CAD
Jan G. Korvink, Henry Baltes
Microsystem technology, which includes semiconductor technology, together with current design methods determine the user requirements of (mu) TCAD tools aimed at microsystem developers. The choice of numerical methods and computer technology complete the specification. In this paper we present a (mu) TCAD system, and show how it is broken up into tasks, individual programs that make up the functional building blocks. Many of these blocks already exist, organized within the (mu) TCAD system and centered around our microsystem simulation kernel SOLIDIS. We illustrate these functional blocks with concrete examples. We conclude by considering the missing links in the (mu) TCAD chain.
Performance trade-offs for a surface micromachined microengine
Samuel L. Miller, Jeffry J. Sniegowski, Glen LaVigne, et al.
An electromechanical model of Sandia's microengine is developed and applied to quantify critical performance tradeoffs. This is done by determining how forces impact the mechanical response of the engine to different electrical drive signals. To validate the theoretical results, model- based drive signals are used to operate actual engines, where controlled operation is achieved for the following cases: 1) spring forces are dominant, 2) frictional forces are dominant, 3) linear inertial forces are dominant, 4) viscous damping forces are dominant, and 5) inertial load forces are dominant. Significant improvements in engine performance are experimentally demonstrated in the following areas: positional control, start/stop endurance, constant speed endurance, friction load reduction,and rapid actuation of inertial loads.
Novel MEMS simulation tool for thermal-based radiation sensors
Nicholas R. Swart, Hubert Jerominek, Philippe Lambert
We report a simulation tool employing the finite element method for thermal-based radiation sensor analysis. Application of the tool to bolometric detectors is described, and simulation examples are given. Excellent agreement is observed between experimental and measured data. In addition, an equivalent circuit model, with pertinent parameters calculated automatically by the simulation tool, is also presented.
Actuators
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Mercury-contact switching with gap-closing microcantilever
Scott Saffer, Jonathan Simon, Chang-Jin Kim, et al.
We present an electrostatically actuated micro-mechanical relay with a stationary mercury micro-drop at the point of contact. The moving element is 2 micrometers thick polysilicon cantilever with widths from 2 to 3 micrometers and lengths from 300 to 500 micrometers made through MCNC multi-user MEMS processes. A technique to selectively form microscale mercury on prescribed sites was used to accomplish mercury- to-electrode contacts for the relays. Measurements of the poly-mercury-poly contact resistance resulted in values that range from 800 to 1000 (Omega) , with most values near 1000 (Omega) . The total resistance of the devices varied from 1.9 k(Omega) to 3.2 k(Omega) depending on the device configuration. The device can switch loads over 10 mA.
Design considerations of the electrical contacts in (micro)relays
Hocine Ziad, Christiaan Baert, Harrie A. C. Tilmans
The electrical contacts are of crucial importance for the ultimate performance of (micro)relays. In this paper, the contact resistance of hard-contact relays is experimentally studied as a function of the contact force, the apparent contact area and the cleanliness of the contact surfaces. A simple test bench set-up is used to measure the contact resistance in air as a function of the contact force and the contact area. Forces range from 50 mgf to several gf. The contacts have a round shape with diameters ranging from 100 micrometers to 500 micrometers . The resistance decreases with increasing force and increasing area. Above force of approximately 2 gf, the contact resistance becomes fairly stable, i.e., independent of the applied force. The contact resistance stabilizes at values varying from 30 to 50 m(Omega) depending on the area. The measured contact resistance values for a 50 mgf contact force scatters between 50 m(Omega) and 0.7 m(Omega) due to the presence of a contaminating film on the contact surfaces. The scatter in measured values reduces to less than 10 m(Omega) when the contact force is around 4 gf, which again emphasizes that a certain minimum force is required for a reliable contact.
Development and fabrication of a rotary micropump and its industrial and medical applications
Thomas Weisener, Gerald Voegele, Mark Widmann, et al.
The development of small pumps in the area of microsystem technology has lead to many different prototypes, mainly using membranes. In contrast to this, a rotary working pump has been developed at Fraunhofer-Institut fuer Produktionstechnik und Automatisierung (IPA) with which both an improvement in output, as well as pressures previously not possible have been reached. After a first prototype pump with an outer diameter of 10 mm an optimized prototype with an outer diameter of only 2.5 mm was fabricated in cooperation with AGIE applying electro-dischange-machining. Presently Fraunhofer IPA is working upon the design of a micromotor with the same functional principles. The applications of the new microhydraulic system are exceedingly numerous and extend from technical to medical products.
Development and manufacturing of a two-dimensional microactuator for moving an optical fiber
Thomas Frank
This paper describes the design, fabrication and testing of an electrodynamical microactuator for moving an optical fiber. This device with two degrees of freedom has a motion range of 200 micrometers . It is used for the alignment of optical fibers in the sub-micrometer range. The positioning of a monomode optical fiber with respect to one or several other optical fibers or an optical chip is possible. As a result of the electrodynamic principle the motion is free of slide and friction. The technologies of wet chemical etching of silicon and galvanic batch-processes are used. The magnetic field is generated by a permanent magnet. Around the magnet surface copper coils are built for the deflection of the magnet in two dimensions.
Flow and Magnetic Sensor
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Thermoelectric CMOS anemometers
Felix Mayer, Marcel Hintermann, Heiko Jacobs, et al.
We report the fabrication, packaging,and characterization of thermoelectric CMOS anemometers. The sensors are fabricated using the commercial 2 micrometers CMOS process of EM Microelectronic-Marin SA, Switzerland, followed by bulk silicon micromachining. They consist of a membrane of the CMOS dielectrics heated by integrated polysilicon resistors. Integrated p-polysilicon/n-polysilicon thermopiles detect wind-induced temperature differences on the membrane. Two devices are reported. The first, on a 1 mm by 1.3 mm die, measures one component of the wind velocity. The second structure, on a 2 mm by 2 mm die, measures the modulus and the direction of the air flow. We demonstrate packaging solutions for both sensors. They are mounted on a standard TO substrate, embedded in epoxy, and mechanically protected by a wire-mesh. The performance of the 2D device is enhanced by a flow concentrator. The sensor responses were characterized in a wind-tunnel as a function of sensor orientation, air velocity, and mesh parameters. The output signals grow monotonically with the air velocity up to 40 mV at 38 ms-1 at a heating power of 3 mW. Angle detection is demonstrated with standard deviation smaller than 13 degrees. Cost-effective batch production and low power consumption make these thermal devices an interesting alternative to conventional, mechanical, anemometers.
Pressure and Strain Sensors
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Analytical techniques for examining reliability and failure mechanisms of barrier-coated encapsulated silicon pressure sensors exposed to harsh media
Gordon Bitko, David J. Monk, Theresa Maudie, et al.
Low-cost, silicon piezoresistive pressure sensors need to be compatible with a variety of chemical environments to provide pressure and liquid level sensing products for various automotive, industrial, and consumer white goods applications. Previous work has identified that the typical failure mechanism for a barrier coated device involves the delamination of the coating from the substrate followed by corrosion of exposed metal areas. This work introduces the application of known electrochemical techniques for the development of accelerated experimental test procedures for sensor exposure to harsh environments. Qualitative correlation of these results with predicted reliability lifetimes, estimated statistically from media exposure testing, is shown. Several methods are presented for assessing the quality of barrier coatings. These techniques can be used both to identify specific corrosive failure mechanisms as they are occurring during media exposure, and to make relative predictions about the reliability lifetime of barrier coated and encapsulated devices. One demonstrated method is the simple measurement of open circuit (non-biased) potential. This is envisaged to show a mixed potential between all anodic and cathodic reactions, while taking into account the resistance of the coating. The fluctuations in mean potential with time depend on variations in the activities of different sensor regions and on underfilm passivation. The standard deviation of voltage noise can be used as an indication of the quality of the coatings. The critical factor in these measurements and sensor encapsulation in general is understanding reactant diffusion through a barrier coating. In addition, polarization measurements were used to examine the rate of media diffusion through the coating and to determine the reaction mechanism.
Planar surface-micromachined pressure sensor with a subsurface, embedded reference pressure cavity
William P. Eaton, James H. Smith
Planar, surface micromachined pressure sensors have been fabricated by an extension of the chemical-mechanical polishing (CMP) process. CMP eliminates many of the fabrication problems associated with the photolithography, dry etch, and metallization of non-planar devices. FUrthermore, CMP adds additional design flexibility. The senors are based upon deformable, silicon nitride diaphragms with polysilicon piezoresistors. Absolute pressure is detected by virtue of reference pressure cavities underneath the diaphragms. Process details are discussed and characteristics from many devices are presented.
Phase-sensitive techniques applied to a micromachined vacuum sensor
Glenn H. Chapman, N. Sawadsky, P. P. S. Juneja
Phase sensitive AC measurement techniques are particularly applicable to micromachined sensors detecting temperature changes at a sensor caused by a microheater. The small mass produces rapid thermal response to AC signals which are easily detectable with lock-in amplifiers. Phase sensitive measurements were applied to a CMOS compatible micromachined pressure sensor consisting a polysilicon sense line, 760 microns long, on an oxide microbridge separated by 6 microns on each horizontal side from similar polysilicon heaters, all over a micromachined cavity. Sinusoidal heater signals at 32 Hz induced temperature caused sense line resistance changes at 64 Hz. The lock-in detected this as a first harmonic sense resistor voltage from a DC constant sense current. By observing the first harmonic the lock-in rejects all AC coupling of noise by capacitance or inductance, by measuring only those signals at the 64 Hz frequency and with a fixed phase relationship to the heater driver signals. This sensor produces large signals near atmospheric pressure, declining to 7 (mu) V below 0.1 mTorr. Phase measurements between 760 and 100 Torr where the air's thermal conductivity changes little, combined with amplitude changes at low pressure generate a pressure measurement accurate at 5 percent from 760 Torr to 10 mTorr, sensing of induced temperature changes of 0.001 degree C.
Strain sensitive resonant gate transistor
Shun-ichi Miyazaki, Takashi Yoshida, Kyoichi Ikeda
The strain sensitive resonant gate transistor working as a strain gauge has been developed. This device is fabricated by using surface micro-machining techniques and CMOS technology. Poly-Si bridge is fixed to the FET structures and the bridge is encapsulated by a Poly-Si cell in order to keep it inside the vacuum. When the strain is applied to the bridge, the resonant frequency is changed. The shift of resonant frequency is converted to the frequency of alternating drain current. Some basically technological problems are in order to realize high sensitivity and reliability in this sensor. As a result, the strain sensitive sensor with the characterizations of high gage factor, high Q factor, no-sticking and wide-working-range is developed. Characterizations of this sensor have been demonstrated.
Poster Session
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Semiconductor acceleration sensor
Katsumichi Ueyanagi, Mitsuo Kobayashi, Tomoaki Goto
This paper reports a practical semiconductor acceleration sensor especially suited for automotive air bag systems. The acceleration sensor includes four beams arranged in a swastika structure. Two piezoresistors are formed on each beam. These eight piezoresistors constitute a Wheatstone bridge. The swastika structure of the sensing elements, an upper glass plate and a lower glass plate exhibit the squeeze film effect which enhances air dumping, by which the constituent silicon is prevented from breakdown. The present acceleration sensor has the following features. The acceleration force component perpendicular to the sensing direction can be cancelled. The cross-axis sensitivity is less than 3 percent. And, the erroneous offset caused by the differences between the thermal expansion coefficients of the constituent materials can be canceled. The high aspect ratio configuration realized by plasma etching facilitates reducing the dimensions and improving the sensitivity of the acceleration sensor. The present acceleration sensor is 3.9 mm by 3.9 mm in area and 1.2 mm in thickness. The present acceleration sensor can measure from -50 to +50 G with sensitivity of 0.275 mV/G and with non-linearity of less than 1 percent. The acceleration sensor withstands shock of 3000 G.
Force measurements of polysilicon thermal microactuators
J. Robert Reid, Victor M. Bright, John H. Comtois
Surface micromachined polycrystalline silicon thermal micro- actuators provide large deflections while requiring low drive voltages and occupying small device areas. The force provided by thermal actuators is not currently known. Therefore, force testers have been designed and fabricated. The force testers were used to measure the force of individual actuators over a range of design parameters including flexure length, hot arm width, arm separation,and actuator thickness. The force testers have also been connected to arrays of 2 to 20 actuators coupled together. Measurements of force tester deflection versus actuator drive power have been taken. The data shows that individual actuators are capable of generating greater than 4.8 micronewtons of force with less than 15 milliwatts of power. The test also show that coupling the actuators together successfully combines the force of individual actuators. These measurements allow the creation of a general set of design rules for efficient thermal actuators.
Industrial microsystems on top of CMOS design and process
Jordi Carrabina, Joaquin Saiz, David Marin, et al.
We propose a design and technology methodology and CAD tools for a microsystems fabrication based on the 1.0 micrometers CMOS from ATMEL-ES2. In order to profit from vendor cell libraries, design kits have to be enhanced to deal with the new conception environment. Main contributions are, sensor dependent technology file, device modeling and automatic generation for different ranges, and adaptation of semi- custom tools (simulation environment and P and R) for complete microsystems design. A library of dedicated sensor cells is being designed using Cadence DFWII and the foundry design kit. These sensors are fabricated with the standard CMOS process plus some post-processing steps. Three levels of post-processing are considered: 1) pH-ISFET sensors fabricated using standard CMOS, 2) gas flow and radiation sensors based on thermopiles using simple post-processing. The post-processing is compatible with the foundry CMOS process. Our technology has been developed up tot he point of maximum simplification that results in the use of only one additional mask for back-side etching. Passivation layer together with oxide windows are used for front-side etching with excellent results.
Innovative frequency measurement technique used in the design of a single channel frequency to digital converter ASIC
Neranjen Ramalingam, Vijay K. Varadan, Vasundara V. Varadan
The frequency to digital converter (FDC) is an application specific integrated circuit. The chip has been designed to handle one input channel but can easily be expanded to handle multiple channels of frequencies. The channel is capable of measuring frequencies from 100 Hz to 100 kHz. The power consumption of the chip is very low. The frequency measurement accuracy is better than 0.1 percent. The conversion rate per channel is 100 samples/second which can be carried too. The chip has a built-in test equipment to verify its operation. It is able to generate frequencies like 8 Mhz, 4Mhz, 2Mhz and 1Mhz which can be fed as optional clock frequencies depending on the accuracy desired. The FDC chip can be interfaced to a 16 bit bus. To meet these stringent specifications of the FDC chip an innovative frequency measurement technique has been devised called the hybrid technique of frequency measurement. The technique proves to be very accurate and it is found that by varying the sampling rate the range of input frequencies over which this accuracy can be achieved also changes. The specifications are particularly strict so that it is possible to use the chip for any military application for which a very reliable operation is demanded. The FDC chip is hence ideal for control and guidance purposes. The chip has wide ranging applications. In conjunction with sensors such as accelerometers it can be used to design smart sensors. The chip can play a vital role in engine controllers and in pressure measurements using vibrating type transducers. Sometimes to isolate transducers, the output is converted to frequency and isolation is achieved using opto-isolators; then by measuring the frequency using this chip this can be converted to digital information.
Numerical analysis of an optical motor based on the radiation pressure
Yoshiro Ohmachi, Kazuhiro Baba, Eiji Higurashi
The radiation force exerted on a transparent disk-type optical rotator with shape dissymmetry is predicted using a x-ray optics model. We performed a quantitative analysis of the torque exerted on the rotator while ion a single-beam gradient-force optical trap. Rotation is due to the optical torque from the laser radiation pressure on the side walls. Thus, the maximum torque is obtained when a large proportion of the laser beam is incident to the side walls. Both the trapping force and the torque depend proportion of the laser beam is incident to the side walls. Both the trapping force and the torque depend strongly on the position of the rotator and the numerical aperture. We also found that there is an optimum value of NA at which the maximum torque is generated. The validity of the ray-optics model for polystyrene latex spheres in the trap was also confirmed by our experimental results. From the experimental rotation speed of the polymide rotator and the numerical results, we quantified the damping factor and the static frictional torque of the rotator.
Plenary Papers
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Application of micromachining technology to optical devices and systems
Micromachine technologies based on IC-compatible micromachining have advantages denoted by three `M's'. Miniaturization is the most popular but Multiplicity, which means the batch fabrication capability of many complicated elements, and Microelectronics to control motions or to add different functions such as the optical function are equally important. This paper deals with the application of micromachine technologies to micro optical devices. A basic concept making the best use of the advantages is proposed. Recent examples of optical microelectromechanical systems are reviewed.
Commercializing MEMS--too fast or too slow?
S. Walsh, W. N. Carr, H. Mados, et al.
MEMS as a technology base is coming of age, butas in any vital process growing pains occur. Commercializing MEMS is simultaneously viewed asagonizingly slow by many ofits promoters and lightingly quick by many companies whose products are being replaced with MEMS based substitutes. This effort ties current efforts in market analysis, technology evaluations, competency based strategy in an effort to understand the pace ofMEMS commercialization.