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Solid-State Sensors and Actuators, 1991. Digest of Technical Papers, TRANSDUCERS '91., 1991 International Conference on

Date 24-27 June 1991

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Displaying Results 1 - 25 of 264
  • The coming opportunities in microsensor systems

    Page(s): 2 - 7
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    Challenges and opportunities confronting the development of integrated sensing systems in the 1990s are discussed. Silicon microsensors can offer significant advantages over alternative technologies, employing features such as self-testing, autocalibration, digital compensation, and bus-compatibility to improve system reliability and performance while reducing cost. A system architecture which permits all of these features to be implemented is described. Each node in this distributed sensing system is composed of sensors, actuators, and a monolithic microprocessor-driven interface chip and is realized as a multichip module. A discrete prototype of this system achieves 12-b accuracy with the ability to read over 700 sensors per second. All data transfers include parity checking and polynomial-based sensor data compensation in the host computer. Over 300 Mbytes of data have been transferred error-free. Needs for further research in these areas are described, and the application of the prototype system to the measurement of pressure, flow, wafer temperature, and other variables in a reactive ion etching system is discussed.<> View full abstract»

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  • Current status and future trends of silicon microsensors

    Page(s): 8 - 13
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    Recent progress that has allowed the fabrication of silicon microsensors using procedures which are compatible with standard IC processes is reviewed. This will facilitate the integration of sensor and actuator units with their associated interface electronics, leading to microsystems. The importance of CAD (computer-aided design) is outlined. These developments are illustrated using examples of accelerometers, resonators, and chemical sensors. Some preliminary results of microsystems, especially regarding miniaturized chemical analysis systems, are discussed.<> View full abstract»

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  • New opportunities for microactuators

    Page(s): 14 - 20
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    Microactuators fabricated by an IC-based micromachining technique are reviewed. The microactuators are driven by various forces suitable in the microdomain. The advantages and the limitations of fabrication processes suggest that microelectromechanical systems (MEMSs) in which microactuators play a key role would be completely different from simple miniaturization of macro-machines. A possible architecture oriented toward MEMSs is a system composed of many smart micromodules, each module having a microactuator, sensors and electrical circuits integrated in itself. As an example, a ciliary motion system and its actuators are explained. Promising applications of MEMSs seem to be in optics, magnetic and optical heads, fluidics, handling cells and macromolecules, and microscopy with microprobes such as scanning tunneling microscopes and atomic force microscopes.<> View full abstract»

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  • Analytical 2D-model of CMOS micromachined gas flow sensors

    Page(s): 22 - 25
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    An analytical 2D model for the theoretical treatment of thermoelectric or thermoresistive integrated gas flow sensors is presented. It allows a detailed understanding and quantitative description of the function of cantilever beam and microbridge sensor structures fabricated using standard CMOS technology followed by an additional etching step. The heat exchange between the solid and the ambient gas along the surface of the respective sensor element is described by a generalized heat transport equation for the spatial temperature distribution. Only a small portion of the Joule heat produced by the integrated heating resistors is transferred to the gas, while the main stream of heat is conducted through the sandwich structure to the bulk silicon. However, there is a significant temperature modulation in the vicinity of the sensor surface, and it is this effect which makes the sensor work. In spite of the simplifying assumptions made, the model reproduces all essential features of the experimental findings and thus may be used to optimize the sensor design.<> View full abstract»

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  • Numerical optimisation of flow-rate microsensors using circuit simulation tools

    Page(s): 26 - 29
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    Numerical simulation results of the steady state thermal behavior in flow-rate microsensors are presented. The results have been obtained using a circuit level CAD (computer-aided design) tool. The various heat transfer mechanisms are suitably reduced into a circuit model by using the linear and nonlinear circuit elements available in SPICE. Good agreement between simulations and measurements has been obtained for realistic values of physical parameters. Both laminar and turbulent gas flow conditions are considered.<> View full abstract»

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  • A micromachined, silicon mass-air-flow sensor for automotive applications

    Page(s): 30 - 33
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    A micromachined, monolithic silicon mass-air-flow sensor has been developed for measuring engine intake air flows in the range of 1-60 m/s. It has a response time of under 1 ms and can be temperature compensated to a deviation of +or-3.5% error or less in indicated flow over a temperature range of -30 degrees C to +40 degrees C. The device can withstand bombardment by particles up to 50- mu m in size in the air stream, or larger ones if elements with reduced accuracy are used. A more rugged design, using larger silicon beams but retaining good temperature compensation capability, can be achieved by modifying the beam ends and their support to increase the thermal isolation between the beams and the rest of the silicon chip.<> View full abstract»

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  • Micro flow sensor and integrated magnetic oxygen sensor using it

    Page(s): 34 - 37
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    A thermal micro mass flow sensor was developed. A micro bridge heater was fabricated by micromachining. The sensor has high sensitivity and quick response because of its small thermal capacity and small thermal time constant. Micro bridge differential heaters were used to detect mass flow in a small flow range. An integrated magnetic oxygen sensor was fabricated using the micro thermal flow sensor. The flow sensor and the micro valve will be applied in integrated gas control systems.<> View full abstract»

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  • Wide range pyroelectric anemometers for gas flow measurements

    Page(s): 38 - 40
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    Studies of pyroelectric anemometers (PAs) have demonstrated that these sensors have an extraordinarily wide operational range and excellent resolution. Measurements were conducted in two structures: a 3.3-mm-diameter pipe with an anemometer located in the center of the pipe and a 4.5-cm-diameter pipe with anemometers placed in the center and on the walls of the pipe. These measurements demonstrated that the PA can detect flows from approximately 1 mL/min to over 20 L/min in the 3.3-mm-diameter tube. Based on the measurements, It is concluded that the PA shows promise as a good flow transfer standard and as a candidate for monitoring extremely low flow rates.<> View full abstract»

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  • A micromachined flow sensor for measuring small liquid flows

    Page(s): 41 - 44
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    A flow sensor for measuring small liquid flows in chemical measurement systems has been fabricated using bulk silicon micromachining techniques. The liquid flow sensor utilizes the measurement principle of thermal transit time, where a heat pulse is injected into the liquid and the velocity of the heat pulse is measured. The sensor consists of a silicon wafer mounted between two glass plates. A flow channel is anisotropically etched into the front side of the wafer, and on the back side electrical components for heat delivery and temperature detection are made. The flow sensor shows excellent accuracy, speed, and long-term stability. Due to the well-defined geometry easily obtainable in this technology, the mechanical, thermal, and flow properties of the flow sensor are very reproducible. There is firm mechanical insulation between the fluid system and the electrical parts of the sensor. Good thermal coupling between the fluid and the temperature controlling components is ensured, since silicon is an excellent heat conductor.<> View full abstract»

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  • Silicon-microactuators: activation mechanisms and scaling problems

    Page(s): 46 - 50
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    Different types of electromechanical microactuators are described and discussed with respect to their most important characteristics (i.e. conversion efficiency, displacement, force, torque, etc.) and power consumption. Different actuation principles can be adapted to IC and micromachining technologies with specific potentials in device miniaturization. An overall evaluation of the different concepts is strongly linked to the specific applications and to the system requirements. Different types of electromechanical silicon microactuators have specific advantages and disadvantages with respect to deflection, force, power consumption, and response time. Some of the conversion principles, especially electrostatically driven structures, offer outstanding qualities with an increasing degree of miniaturization.<> View full abstract»

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  • The integration of micro-machine fabrication with electronic device fabrication on III-V semiconductor materials

    Page(s): 51 - 54
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    The authors have fabricated a variety of micromechanical devices on GaAs and InP substrates, using fabrication methods and materials compatible with microelectronic device fabrication on III-V compounds. The actuators are electrostatically operated and include microwave switches, linear actuated microwave tuners, and rotating element motors. The authors describe the types of mechanical devices that have been fabricated, the fabrication strategy, sequence, methods, and materials used in the fabrication, the compatibility of processes with III-V based devices, and some evaluations of their mechanical and electrical properties.<> View full abstract»

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  • Linear motion microactuators using piezoelectric thin films

    Page(s): 55 - 58
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    Two novel types of microactuators for linear displacements are presented which use piezoelectric thin films for the electrical-to-mechanical energy process. One actuator uses a folded path or meander line geometry to produce tethered linear displacements. The other actuator uses an inertial recoil mechanism in conjunction with an electrostatic clamp to produce incremental stepping motion. Sufficient repetition of the stepping sequence produces virtually unlimited travel range, being limited by practical considerations such as electrical connections. Electromechanical models for both actuators are developed and are used to quantitatively estimate the performance of actuators designed to a particular set of dimensions. Fabrication procedures for making both microactuators have been developed, and the status of the fabrication efforts is presented.<> View full abstract»

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  • Operation of harmonic side-drive micromotors studied through gear ratio measurements

    Page(s): 59 - 62
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    The detailed operation of variable capacitance harmonic (or wobble) side-drive micromotors was studied through gear ratio measurements. The gear ratio of the wobble micromotor is affected by wear in the bearing and by rotor slip. Rotor slip is a function of motive torque magnitude, excitation angle, and friction torques. The gear ratio of a wobble micromotor can be expressed as a constant term plus a term that accounts for rotor slip. The constant term is the nominal gear ratio which is equal to the bearing radius divided by the bearing clearance. The rotor slip term is directly proportional to the bushing friction torque and inversely proportional to the square of the excitation voltage. Micromotor operation in air as opposed to nitrogen demonstrates a significantly larger bushing friction torque.<> View full abstract»

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  • Electrostatic parallelogram actuators

    Page(s): 63 - 66
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    Surface micromachined actuators composed of polysilicon, parallelogram flexible supports are described. The parallelogram actuators transform both the direction and the magnitude of the attractive, electrostatic force developed between the drive electrodes. In a typical configuration, one vertex of the parallelogram is fixed, two opposing, suspended vertices are pulled by the attractive electrostatic force, and the fourth, suspended vertex moves towards the fixed vertex. Parallelogram actuators with beam lengths of 200 approximately 600 mu m and beam widths of 2 approximately 7 mu m were fabricated in 4- mu m-thick LPCVD (low-pressure chemical vapor deposited) polysilicon. Best device yields were obtained when a t-butyl alcohol freeze-dry rinse was used. A parallelogram actuator with 283- mu m-length and 2.5- mu m-width beams moved repeatably and showed 5- mu m displacement by an applied voltage of 19 V.<> View full abstract»

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  • Molecular assembling technology for electrochemical and optical enzyme-sensing films

    Page(s): 68 - 73
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    Several different molecular film technologies have been developed for fabricating biosensors, including electrochemical codeposition of nonconductive polymer film and enzyme; electrochemical fabrication making a molecular interface of conductive polymer for an enzyme; and protein LB film fabrication. A microenzyme sensor for glucose was fabricated by electrochemical codeposition. An amperometric enzyme sensor was fabricated by incorporating the alcohol dehydrogenase-NAD-mediator system in a conductive polymer membrane. The protein LB film fabrication was used to produce an optical enzyme sensor for triglyceride.<> View full abstract»

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  • Rapid determination of cellular metabolic rates with a silicon microphysiometer

    Page(s): 74 - 77
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    The microphysiometer is a silicon-sensor based instrument designed to measure the metabolic rates of small numbers of living cells. By improving the electronic noise level of this instrument, the authors have increased the temporal resolution of metabolic rate measurement by about an order of magnitude compared to previous versions of the instrument. This enables the study of relatively fast cellular responses to receptor/ligand binding. Results obtained with a cell line (TE671) that is known to contain acetylcholine receptors are presented. The kinetics of the cellular response to an acetylcholine agonist is shown to be complex, with three distinct resolvable phases. Through pharmacological manipulations it is demonstrated that the response is due to a muscarinic acetylcholine receptor.<> View full abstract»

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  • New semiconductor glucose sensor using sputtered LaF/sub 3/ film

    Page(s): 78 - 81
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    A sputtered LaF/sub 3/ (solid electrolyte) film was used to construct a novel MOS=type glucose sensor. The sensor, having a structure of GOD (glucose oxidase) immobilized film/Pt/LaF/sub 3//SiO/sub 2//Si/Al multiple layers, needs no external reference electrode. A stable response was obtained in the glucose concentration range from 2*10/sup -4/ to 2*10/sup -2/ M in a phosphate buffer solution of pH 6.9, with a 90% response time of ca. 1 min. Preliminary discussions on the response mechanism are also presented.<> View full abstract»

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  • Microfabricated microhaemorheometer

    Page(s): 82 - 84
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    The authors investigate the application of silicon micromachining techniques to the measurement of erythrocyte deformability, a physiological parameter strongly linked to many aspects of cardiovascular disease. They provide an overview of microscopic blood flow-microhaemorheology, a topic which is intimately related to erythrocyte deformability. The need for refined techniques to measure deformability is derived from a critique of existing techniques. The specification of a more capable microhaemorheological instrument and discussion of the advantages of a microfabricated silicon implementation are given. A description of a particular implementation consisting of a bulk micromachined two-layer silicon-silicon device is outlined, with details of its fabrication steps, support system, and modus operandi. Initial experimental performance indications are described.<> View full abstract»

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  • Monitoring of blood pO/sub 2/ with a thin film amperometric sensor

    Page(s): 85 - 87
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    A sample-taking sensor system for online pO/sub 2/ monitoring of blood is described. The system consists of a two-lumen catheter with a thin-film amperometric sensor cell, a pump unit with instrumentation, and a personal computer. The planar three-electrode system is only covered by a hydrophilic pHEMA membrane to avoid alterations in the composition of any internal electrolyte solution. To overcome the problem of electrode poisoning, the surface of the working electrode is regenerated during the calibration mode of the calibration/measurement cycle. Animal studies have been performed with anaesthetized pigs. The comparison of the sensor values with blood gas analyzer data shows a curved but reproducible correlation.<> View full abstract»

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  • Vibration rectification in silicon micromachined accelerometers

    Page(s): 89 - 92
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    The phenomenon of vibration rectification in silicon accelerometers is described. Examples of the effect are looked at for the case of piezoresistive silicon micromachined accelerometers. Quad-beam (doubly clamped) devices are compared to dual-beam (simple cantilever) devices. It is shown that for dual-beam accelerometers, the majority of vibration rectification can be attributed to simple quadratic nonlinearity of the accelerometer response and that the other rectification effects are at least an order of magnitude lower. The dual-beam devices perform substantially better than quad-beam devices. It is noted that this effect should be considered when applying these devices to DC measurements, especially when high levels of vibration may be present.<> View full abstract»

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  • A new sense element technology for accelerometer subsystems

    Page(s): 93 - 96
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    The author describes a capacitive accelerometer technology using sense element structures fabricated on the surface of a substrate or wafer. The sense element consists of an asymmetrically shaped flat plate of metal supported above a substrate surface by two torsion bars mounted on a central pedestal. The sense element is free to rotate around the torsion bars. Capacitor plates located on the substrate surface are used to detect the rotation. Fabrication of sense elements is done by selective electroforming in which a metal is electroplated onto a conductive substrate through a patterned photoresist layer. To produce suspended sense elements, the sense elements are fabricated partially on the top of a sacrificial spacer material deposited earlier. After the sense elements have been formed, the spacer material is then selectively etched, leaving the sense element supported only where it was formed directly on the substrate surface.<> View full abstract»

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  • A highly symmetrical capacitive micro-accelerometer with single degree-of-freedom response

    Page(s): 97 - 100
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    It is shown how a micromachined capacitive sensor can be constructed that is able to perform acceleration measurements with over 80 dB dynamic range at less than 1% nonlinearity. Mechanical symmetry alone, without any electrical compensation, accounts for extremely low off-axis and rotational sensitivities. Viscous flow of helium gas controls damping, and the gas pressure can be used to set bandwidth, which is typically on the order of 500 Hz for a 50 G device. The main device characteristics are the exclusive response to a translational acceleration component in a single axis, maximized sensitivity for a given chip area, and improved linearity by suppression of error sources such as fringing field effects, stray capacitances, leakage resistances, and electrostatic pressure. Typical applications are the medium to low frequency, high-sensitivity areas where a uniaxial response is imperative. Robot endpoint control and space or airborne navigation are examples of such areas.<> View full abstract»

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  • A micromechanical structure eliminating lateral effect of silicon accelerometer

    Page(s): 101 - 103
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    A novel two-mass micromechanical structure for a silicon accelerometer is described. In this structure, each mass is attached to the rim by two beams and a fifth beam bridges the two masses at the central area of the structure. An acceleration normal to the device plane can bring about significant stress in the central beam area while any lateral acceleration in a direction in the device plane has very little effect on the stress to the first order of approximation. As the stresses in the central beam area are of a single sign and change very little on position, four piezoresistors can be located on the central beam area to form a Wheatstone bridge or a single-element Hall-type strain gauge can be used to sense the normal acceleration with little interference by lateral accelerations. Preliminary results on the device are presented.<> View full abstract»

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  • A simple, high performance piezoresistive accelerometer

    Page(s): 104 - 107
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    The author describes the structure, manufacture, and performance of a 1000 g full-scale piezoresistive accelerometer. This accelerometer has a very high resonant frequency, nominally 65 kHz, and is designed to have a sensitivity of 0.2 mV/g. The design is executed in (110) silicon. The piezoresistors and inertial system are formed in one etching step. The piezoresistors are suspended between the inertial mass and support rim, and are very small in volume, 7.8*10/sup -10/ cm/sup 3/, thus needing very small strain energy.<> View full abstract»

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  • Motion investigation of electrostatic servo-accelerometers by means of transparent ITO fixed electrodes

    Page(s): 108 - 111
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    The authors introduce a novel thin film material for sensors and actuators: indium tin oxide (ITO). ITO has the unique feature of combining low electrical resistivity and high visual transparency. Thin ITO films were deposited by DC-sputtering to form the fixed electrodes of a capacitive servo-accelerometer. Since the movable electrode of the accelerometer is visible during real operation of the sensor, its behavior can be studied under various conditions. One investigation presented is a study of the motion of the movable electrode at high electrostatic voltages, and its effect on the measurement range of the sensor. The benefits of ITO for mass production are illustrated by means of the evaluation of the temperature behavior of the accelerometers.<> View full abstract»

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