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Abstract
This paper considers the rapidly-developing field of integrated sensors, in which one or more transducers are joined with custom interface circuitry on a single chip. Many of the issues confronting continued development in this are discussed, including process compatibility and circuit partitioning. Backed by an increasingly powerful array of solid-state process technologies, integrated sensors are expected to be widely applied to extend microcomputer-based control in a variety of areas.
... Almost exclusively, these sensors combine a discrete gas sensing element-fabricated through a specialized process-and are combined with a separate drive and signal conditioning circuit. It has been the aspiration of researchers for more than 20 years to combine the different parts of a gas sensor with microelectronics in order to create an integrated or smart gas sensor [1]- [8]. However, the single most significant impediment to having the widespread application of gas sensors is their price. ...
... Traditionally, the very large resistance of sensing films (for example metal oxides) can be reduced by using interdigitated electrodes with high aspect ratios (thousands). The higher the aspect ratio ( ) of the electrodes the more they can reduce the resistance ( ) of the sensing material, thus (1) where is the number of fingers of the interdigitated electrode, is the length of the fingers, and is the distance between adjacent fingers. ...
... To simplify the discussion we have subdivided the integrated circuits into the two different sensing techniques, which dominate the gas sensor market, namely resistive and electrochemical. 1 In addition to these gas sensor types, we will consider a number of different heater drive circuits (not required for electrochemical). ...
Modern gas sensor technology is becoming an important part of our lives. It has been applied within the home (monitoring CO levels from boilers), the workplace (e.g., checking levels of toxic gases) to healthcare (monitoring gases in hospitals). However, historically the high price of gas sensors has limited market penetration to niche applications, such as safety in mines or petrochemical plants. The high price may be attributed to several different components: (1) cost of a predominantly manual manufacturing process; (2) need for interface circuitry in the form of discrete components on a PCB; and (3) fireproof packaging, making the cost of gas detection instruments typically many hundreds of dollars. Consequently, there has been a considerable effort over the past 20 years, towards the goal of low-cost ($1-$5) gas sensors, employing modern microelectronics technology to manufacture both the sensing element and the signal conditioning circuitry on a single silicon chip. In this paper, we review the emerging field of CMOS gas sensors and focus upon the integration of two main gas-sensing principles, namely, resistive and electrochemical and associated circuitry by CMOS technology. We believe that the combination of CMOS technology with more recent MEMS processing is now mature enough to deliver the exacting demands required to make low-power, low-cost smart gas sensors in high volume and this should result in a new generation of CMOS gas sensors. These new integrated, mass-produced gas sensors could open up mass markets and affect our everyday lives through application in cars, cell phones, watches, etc.
... Work on multi-sensor micro-instrumentation systems combining sensors and electronics and wireless interfaces started at Michigan in the early 1990s and led to the demonstration of some of the earliest miniature, low-power, wireless sensor modules [1,2]. The WIMS Center was launched in 2000 at the University of Michigan with funding from the US National Science Foundation to conduct basic research and development of all the critical components of microsystems in areas of sensors/actuators, lowpower circuits for signal processing, innovative technologies including RF MEMS for low-power wireless links, new hermetic/vacuum packaging techniques, and active and passive power sources and energy harvesting from the environment [3]. ...
... In the seventies integrated infrared sensors were employed, which joined a circuit and their control was done from a microcomputer. These systems did not present economic merits, since implementation costs were very high due to their inflexible technology, which required new infrastructure for implementation and they did not reflect the energy savings [66]. In 1982, the College of Engineering of the University of Florida developed an optimization algorithm for energy management to reduce the cost of electricity watching the price structure and the time usage or demand, simulating with a computer the electric energy needs of a typical residence for testing the effectiveness of the algorithms [67]. ...
... Sensors are widely used electronic devices which detect specific the characteristics of their surroundings and are present in a wide variety of applications such as electronics, aerospace, medicine, robotics, and machinery [136][137][138][139][140][141][142]. Types of sensors include temperature, pressure, humidity, gravity, sound, and vibration sensors [143][144][145][146][147][148][149][150]. ...
Textile-based electronic components have gained interest in the fields of science and technology. Recent developments in nanotechnology have enabled the integration of electronic components into textiles while retaining desirable characteristics such as flexibility, strength, and conductivity. Various materials were investigated in detail to obtain current conductive textile technology, and the integration of electronic components into these textiles shows great promise for common everyday applications. The harvest and storage of energy in textile electronics is a challenge that requires further attention in order to enable complete adoption of this technology in practical implementations. This review focuses on the various conductive textiles, their methods of preparation, and textile-based electronic components. We also focus on fabrication and the function of textile-based energy harvesting and storage devices, discuss their fundamental limitations, and suggest new areas of study.
... Another research thrust is the full integration of microfabricated or MEMS-type (Micro Electro Mechanical Systems) conductometric gas sensors with the managing and signal conditioning electronics at a single chip [163][164][165][166][167][168]. Fig. 14 shows the example of such an integrated conductometric gas sensor. ...
Engineering approaches designed to improve parameters of conductometric gas sensors are being considered in this survey. In particular, in this paper we have analyzed engineering approaches used both for improvement of sensor stability and reliability, and for decrease of power dissipated by conductometric gas sensors. Analysis has shown that those engineering approaches can eliminate some genetic disadvantages of conductometric gas sensors, provide a significant improvement of their exploitation parameters, and expand their application in various fields.
... In the literature, there are several general and many more application specific definitions given for sensors [3][4][5][6][7][8][9][10]. ...
Describes the improvements that smart sensors will bring to electronic
measurement and control systems, and the advantages of using integrated
sensors. Outlines the problems encountered when designing integrating
electronics for use on a smart sensor chip and lists the major functions that
smart sensors must perform. Concludes that the solution to many real life
sensor problems will only be found when a well designed “care-free”
intelligent sensor can be produced and continues that the way to realize this
concept is to combine a sensor device with a number of micro-electronic
components into a single sensor package.
... At the beginning of the eighties the field really started to erupt with the realization that in order to take advantage of the rapid progress in microcomputers and microprocessors, peripheral devices, i.e., sensors and actuators, needed to follow suit. The interfacing of electronics to a non-electronic world [1] became a growing topic that by its very nature attracted scientist from many disciplines and to this day remains an exciting area. The conversion of signals into the electrical domain was nicely illustrated on the cover of the Transducers '83 Abstract Book shown in Fig. 1. ...
The earliest reports of integrated chemical sensor–actuator devices to perform coulometric acid–base titrations date back almost 20 years. Recently a first commercial instrument appeared that allows to perform very rapid, accurate acid–base determinations with a solid-state probe and no need for liquid titrants. This paper reviews some of the early developments and shows the effort that has been undertaken to bring this technology to routine use in the analytical laboratory and beyond.
Growing electricity demand, the deployment of renewable energy sources and the widespread use of smart home appliances provide new opportunities for home energy management systems (HEMSs), which can be defined as systems that improve the overall energy production and consumption of residential buildings by controlling and scheduling the use of household equipment. By saving energy, reducing residential electricity costs, optimizing the utilization rate and reliability of utility companies’ power systems, and reducing air pollution for society, HEMSs lead to an enhancement in the socioeconomic development of low-carbon economies. This review aims to systematically analyze and summarize the development trends and challenges of HEMSs in recent years. This paper reviews the development history of the HEMS architecture and discusses the characteristics of several major communication technologies in the current HEMS infrastructure. In addition, the common objectives and constraints related to scheduling optimization are classified, and several optimization methods in the literature, including various intelligent algorithms, have been introduced, compared, and critically analyzed. Furthermore, experimental studies and challenges in the real world are also summarized and recommendations are given. This paper reveals the trend from simple to complex in the architecture and functionality of HEMSs, discusses the challenges for future improvements in modeling and scheduling, and shows the development of various modeling and scheduling methods. Based on this review, researchers can gain a comprehensive understanding of current research trends in HEMSs and open up ideas for developing new modeling and scheduling approaches by gaining insight into the trade-offs between optimum solutions and computational complexity.
Fibers are low-cost substrates that are abundantly used in our daily lives. This review highlights recent advances in the fabrication and application of multifunctional fibers to achieve fibers with unique functions for specific applications ranging from textile electronics to biomedical applications. By incorporating various nanomaterials such as carbon nanomaterials, metallic nanomaterials, and hydrogel-based biomaterials, the functions of fibers can be precisely engineered. This review also highlights the performance of the functional fibers and electronic materials incorporated with textiles and demonstrates their practical application in pressure/tensile sensors, chemical/biosensors, and drug delivery. Textile technologies in which fibers containing biological factors and cells are formed and assembled into constructions with biomimetic properties have attracted substantial attention in the field of tissue engineering. We also discuss the current limitations of functional textile-based devices and their prospects for use in various future applications.
Die vorangehenden Kapitel zeigen, wie mit Hilfe der modernen Halbleitertechnologie ganze Meßketten für alle wichtigen physikalischen Größen vom Sensor bis hin zur Übertragung und Verarbeitung der Signale aufgebaut werden können. Bei den meisten technischen Anwendungen werden mehrere Meßketten zu einem Sensorsystem zusammengefügt. Dieses Kapitel gibt einen Überblick über die Signalverarbeitung in Sensorsystemen und umfaßt hier die Aufnahme mehrerer Meßgrößen, die Übertragung der zugehörigen Meßsignale und ihre Auswertung. Je nach der Funktion, die das Sensorsystem erfüllen muß, entsprechen die Meßgrößen entweder einer einzigen physikalischen Größe oder verschiedenen physikalischen Größen. Diese Unterscheidung bietet eine — wenn auch grobe—Möglichkeit, die Vielzahl der Sensorsysteme in zwei Klassen aufzuteilen.
Die vorangehenden Kapitel zeigen, wie mit Hilfe der modernen Halbleitertechnologie ganze Meßketten für alle wichtigen physikalischen Größen vom Sensor bis hin zur Übertragung und Verarbeitung der Signale aufgebaut werden können. Bei den meisten technischen Anwendungen werden mehrere Meßketten zu einem Sensorsystem zusammengefügt. Dieses Kapitel gibt einen Überblick über die Signalverarbeitung in Sensorsystemen und umfaßt hier die Aufnahme mehrerer Meßgrößen, die Übertragung der zugehörigen Meßsignale und ihre Auswertung. Je nach der Funktion, die das Sensorsystem erfüllen muß, entsprechen die Meßgrößen entweder einer einzigen physikalischen Größe oder verschiedenen physikalischen Größen. Diese Unterscheidung bietet eine — wenn auch grobe — Möglichkeit, die Vielzahl der Sensorsysteme in zwei Klassen aufzuteilen.
There is a need for efficient diagnostic procedures for evaluation of the current capacity of a structure, monitoring of load and resistance history, and evaluation of the accumulated damage. The available diagnostic techniques are reviewed. They include the methods based on various interrogating media: electromagnetic wave, stress wave, electricity, magnetism, and charged particles. Also considered are the approaches to signal processing. Failure detection and isolation procedures developed in other branches of engineering are summarized. The current trends in the development of new techniques are discussed. The areas considered include microwave, acoustic and optical techniques, integrated sensor systems and motion measurements. Currently used bridge load monitoring procedures are also summarized.
Die vorangehenden Kapitel zeigen, wie mit Hilfe der modernen Halbleitertechnologie ganze Meßketten für alle wichtigen physikalischen Größen vom Sensor bis hin zur Übertragung und Verarbeitung der Signale aufgebaut werden können. Bei den meisten technischen Anwendungen werden mehrere Meßketten zu einem Sensorsystem zusammengefügt. Dieses Kapitel gibt einen Überblick über die Signalverarbeitung in Sensorsystemen und umfaßt hier die Aufnahme mehrerer Meßgrößen, die Übertragung der zugehörigen Meßsignale und ihre Auswertung. Je nach der Funktion, die das Sensorsystem erfüllen muß, entsprechen die Meßgrößen entweder einer einzigen physikalischen Größe oder verschiedenen physikalischen Größen. Diese Unterscheidung bietet eine — wenn auch grobe — Möglichkeit, die Vielzahl der Sensorsysteme in zwei Klassen aufzuteilen.
This paper aims to locate an optimal sensor position using computational fluid dynamic analysis to reduce accidents due to emission of toxic gas in industries. The commercial CFD softwares Gambit and Fluent are used in creating a realistic environment at low cost to simulate flow on the surface of Sensing objects for tracing emission of toxic gas. A three dimensional flow of methyl-iso cyanate (h2cncho) with density ρ=1kg/m3 and coefficient of viscosity μ=1.72e-05 kg/m-s is simulated under steady and unsteady state conditions to study laminar and turbulent flow patterns. Four different surfaces of the Sensing objects namely spherical surface, cylindrical surface, cubical surface and prism surface were considered for analysis and the results are compared. Low velocity observed at the upstream and downstream sides of the surface of Sensing objects indicates that the toxic plumes are captured effectively by the Sensing objects at those points. Hence these points serve as the optimal sensor position. The flow pattern provides an useful insight for the design of the surface of Sensing objects in order to sense quickly and effectively to reduce accidents in industries due to emission of toxic gas and also to protect human health from the risk of inhaled toxic materials to a great extent.
This paper presents and demonstrates the development of flexible tactile sensor utilizing the microstructures of onion epidermal cells, which replace the intermediate dielectric layer in a typical parallel-plate capacitive sensor. The onion epidermal cells can effectively reduce the complexity of the sensor structure and thus simplifies the device fabrication process. The single layer of the onion epidermal cells is robust for high tactile sensitivity, mechanical flexibility and optical transmittance with potentially low-cost sensor manufacturing in a large area. The 4 × 4 tactile sensor array with the total area of 20 × 20 mm2 is demonstrated. A single tactile sensor has the initial capacitance of 9 pF without applying external pressure. The force ranging from 0 N-2 N (20kPa) is applied for sensor characterization. The sensitivity of the sensor is 0.14/kPa. The fabricated sensor shows high sensitivity and linearity. The proposed sensor array will be applied in robotic electronic skin and biomedical devices in the future.
Sensors incorporated with dedicated signal processing functions are called “intelligent sensors” or “smart sensors.’ This chapter discusses the concept of intelligent sensors. Sensor intelligence performs a distributed signal processing in the lower layer of the sensing system hierarchy. The role of the signal processing function in intelligent sensors can be summarized as: (1) reinforcement of inherent characteristics of the sensor device, and (2) signal enhancement for the extraction of useful features of the objects. The most popular operation of reinforcement is compensation of characteristics and the suppression of the influence of undesired variables on the measurand. The goals of signal processing are to eliminate noise and to make the feature clear. Signal-processing techniques mostly utilize the differences in dynamic responses to signal and noise and are divided into two different types, frequency-domain processing, and time-domain processing. The most important role of sensor intelligence is to improve signal selectivity of individual sensor devices in the physical world. This includes simple operations of output from multiple sensor devices for primary feature extraction, such as primary image processing. The role of intelligence in the middle layer is to organize multiple outputs from the lower layer and to generate intermediate output. The most important role is to extract the essential feature of the object. In the processing system in the middle layer, the output signals from multiple sensors are combined or integrated. The extracted features are then utilized by upper layer intelligence to recognize the situation. This processing is conducted in the logical world.
A resonant silicon beam force sensor with piezoelectric excitation and detection is being developed. The realization is based on IC and thin-film technology with ZnO as the piezoelectrical layer. The theory, realization and measurements of a bent-frame sensors are described. A frequency shift of about 3.3 times the unloaded resonance frequency f0 (f0 congruent 6 kHz) is measured with an external load force up to 0.4 N. The absolute sensitivity of the force sensor is 64 kHz/N and the full-scale sensitivity is 29 kHz/N. Using a simple model for the load-force transduction from external to sensor force, the measurements are in good agreement with the theory.
Various devices are described which record physical phenomena and which respond by transmitting signals via information processing units to actuators. For example, a thermistor senses temperature and transmits an electrical signal to an integrated circuit which may in turn actuate a furnace control. This review emphasizes the structure-property relationships of the sensor materials. An ionic conductor, such as stabilized zirconia, can be used to detect oxygen in air/fuel mixtures; metal oxides of large surface area can monitor humidity by surface conduction; and semiconducting transition-metal oxides can measure pH. The mechanism of vanadium dioxide critical temperature thermistors is described; as well as the operation of thermistors of negative and positive temperature coefficients (NTC and PTC) made from, for example, doped nickel oxide and barium titanate respectively. Composite sensors of two or more phases have properties which are the product of those of the individual components and have wide application. For example, combining the Hall effect with electrical conductivity will give magnetoresistance, a property which can be used in a composite magnetic field sensor. Two non-magnetoelectric materials can be cleverly combined to form a magnetoelectric composite. A composite material will exhibit only those symmetry elements that are common to its constituent phases and to their geometrical arrangement. The microstructures are given of composite thermistors and humidity sensors. A variety of integrated sensors can be built into single-crystal silicon chips to detect gases and to act as accelerometers, their fabrication involving micromachining and both isotropic and anisotropic etching.
Most sensors are based on elements of which one of the parameters (resistivity, dielectric constant, Hall voltage, signal frequency, etc.) shows a small change in response to one or more measurands. To apply sensors is a system, an intimate knowledge of the working of the sensor element is usually necessary.The new age of sensors has come about with the development of planar silicon (and GaAs) technology, permitting the integration of sensor elements and signal conditioning circuitry on one chip. This approach might eventually lead to a family of sensors with a microprocessor-compatible output as shown in Fig. 1, which can easily be applied in bus-organized data-acquisition systems [1, 2]. An intermediate and necessary step to reach this ambitious goal is the design of sensors with a digital or frequency output. In this paper the most important techniques and structures are reviewed.
Le développement de la microinformatique ouvrant la voie à une tendance croissante d'automatisation et de contrôle (processus industriel, environnement médical, social, recherche…) fait apparaître de nouveaux besoins “péri-informatiques“, tels que capteurs, moyens de visualisation, actuateurs, éléments de protection et de stockage d'énergie, etc…, destinés à permettre la création de systèmes fiables assurant de nouvelles fonctions, à des coûts compatibles avec les marchés potentiels. Dans cette situation, l'utilisation sur des matériaux nouveaux des moyens technologiques qui ont permis le développement de la microélectronique, peut entrainer la création de nouvelles familles de composants insérables dans des systèmes fonctionnels. Cette approche peut mettre en valeur les avantages bien connus de la technologie microélectronique tels que la haute sophistication, la fiabilité, la reproductibilité, la faisabilitéà faible coût et, à terme, l'intégralité des fonctions, conséquence de la compatibilité technologique. Les conducteurs super-ioniques peuvent trouver de vastes domaines d'applications répondant à certains des besoins indiqués plus haut.
Un premier exemple de ces applications est donné par la nécessité du contrôle de la combustion dans les moteurs à explosion ou dans les brûleurs, correspondant à un marché de très grande diffusion. Nous allons montrer que des capteurs de composition chimiques permettant la régulation des organes de combustion avec des mélanges air/combustible variables peuvent être réalisés dans l'approche “microionique”. Il s'agit de capteurs réalisés collectivement avec des techniques de couches minces et de couches epaisses. Cette démarche apporte non seulement des avantages au niveau de l'interchangeabilité, la reproductibilité et le faible coût, mais aussi la possibilité de réaliser des fonctions plus complexes que celles accessibles par les méthodes traditionnelles. L'extension de cette approche à la détection d'autres espèces, tels que les composés de l'hydrogène, basée sur l'utilisation de conducteurs protoniques, suggère le caractère général de sa validité. Nous allons aussi illustrer l'intérêt de l'intégration de ces conducteurs protoniques solides dans des cellules électrochromes. Ces exemples posent le problème général de l'adaptation de ces matériaux complexes que sont les conducteurs superioniques à de nouvelles méthodes de préparation en couches, et à celui de la conservation de leurs propriétés physiques.
Outlines the current research work on intelligent sensors and
intelligent transducers which will be required in complex systems. Discusses
the elements of an intelligent sensor and concludes that these require
analogue filtering, data conversion and compensation, and a digital
communication link to a common signal bus. Explains what is meant by a
systems approach to intelligent sensors with layered information processing.
Concludes that unless a deeper understanding of the basics of sensor systems
is acquired new intelligent sensor design will be very difficult.
The authors report the results of measurement of the piezoresistance of silicon-on-insulator (SOI) films produced using the zone-melting-recrystallization (ZMR) process. Silicon on insulator piezoresistors were fabricated on SOI wafers which were diced to form 0.5" by 1.5" beams. These beams were clamped at one end and deflected at the other, varying the stress in the piezoresistors. Measurements were conducted at dopant densities ranging from 5*1017 cm-3 to 1.8*1019 cm-3 while varying the temperature from 25 degrees C to 150 degrees C. The data were analysed to determine the gauge factor and its temperature coefficient. These results are compared with published data on the piezoresistance of diffused resistors fabricated in single-crystalline silicon. It has been determined that piezoresistors fabricated using ZMR have gauge factors equivalent to single-crystalline silicon but differ somewhat in the temperature coefficients of gauge factor and resistance.
A novel technology for manufacturing thin silicon diaphragm structures is presented. Controllability of thin silicon diaphragm is one of the most important issues in fabricating silicon micromechanical sensors whose sensitivity depends on the diaphragm thickness. This can be accomplished by epitaxial lateral overgrowth (ELO) of single crystal silicon on a patterned layer of masking material, typically Si02, combined with crystallographic etching of which etching rate depends on the crystal plane. With recent improvement of EL0 material, good quality of lOμm thick, 200μm x lOOOμm single crystal silicon was obtained with its thickness being precisely controlled by growth rate (≤ lμ m/min.). The junction leakage of the p-n junction diodes fabricated on merged EL0 silicon indicated the material quality is comparable to the substrate silicon. Using this technology, a bridge-type piezoresistive accelerometer with four beams and one proof mass was fabricated successfully. Its sensitivity and resonant frequency were comparable to the accelerometers made by other methods. They were analyzed by comparing the experimental results to a simple analytical solution as well as ANSYS stress simulator using a finite element: methods. The experimental results showed a potential application of the new technology to silicon sensor fabrication but some further refinement is remaining. Free-standing single crystal cantilever beams were fabricated using, MELO and RIE, of over lOOOμm long and 5μm by 10μm in cross section. These beams were very short, straight, indicating little residual stress. Wide, short beams were fabricated using EL0 which were also free standing. Special treatment of MELO indicated that diodes and bipolar transistors fabricated on top of the oxide stripes showed nearly ideal characteristics, hence the quality of the MELO was improved. With MELO of thicker than 5μm, no voids were observed. Test structures significantly with all surface micromachining, were designed for further development of silicon membranes.
An 8 × 8-element silicon-based tactile imager fabricated using integrated-circuit process technology is described. The imager consists of an X-Y organized array of capacitive force sensors on 2-mm centers. Each transducer has a zero-pressure capacitance of 1.6 pF, an average sensitivity of 60 mV/g, and a maximum operating force of about 10 g/element. The operating force can be scaled over a wide range without changing the process or lateral array dimensions. The array is read out using a switched-capacitor charge integrator which has been shown capable of a resoiutionof about 1 fF(5 fC), giving a resolution for the imager itself (pad excluded) of more than 8 bit. The readout scheme permits off-chip electronics to be used so that the fabrication sequence requires only five noncritical masks. The array is addressed as a memory, with an access time of less than 20 µsec for 8 pixels. Scaling of the array size to other dimensions is examined and performance limitations are discussed.
The various mechanisms responsible for temperature sensitivity in silicon piezoresistive pressure sensors are described. As a representative transducer, a full-bridge device having a 1-mm-square 23-µm-thick diaphragm is used. The 200 Ω/square, 2K-Ω bridge resistors produce a pressure sensitivity of 13.3 µV/V.mmHg with a temperature coefficient of -1300 ppm/°C. Variability in this sensitivity is most strongly influenced by the diaphragm thickness and the absolute resistor tolerance. A new technique-the electrochemical EDP etch-stop-is found to offer significant advantages over alternative schemes for diaphragm formation. Temperature sensitivity in electrostatically-bonded, vacuum-sealed devices is dominated by resistor match, with oxide stress and junction leakage current playing relatively minor roles over the -40 to + 180°C temperature range. While individual pressure trims for offset and sensitivity will continue to be required, individual temperature trims may be eliminated in these devices for many applications as increasingly precise resistor processes are used.
A new generation of implantable, telemetric transmitters for intracranial pressure (ICP) measurements have been developed. A unique technique used in packaging the silicon piezoresistive pt essure transducer provides excellent long-term stability. Pulse code modulation is used for data transmission over a radio frequency (RF) link. To minimize the component count, two semicustom, bipolar integrated circuits are used. The transmitter electronics are housed inside a 29 Ã20 Ã7 mm titanium package along with the pressure transducer and two lithium batteries. Even though the transmitter consumes less than 0.4 mW of power, it is turned on remotely via RF signal transduction only on demand in order to extend the lifetime of the batteries to years. The pressure input of the transmitter has a dynamic range of ¿100- +200 mmHg with a 0.3 mmHg resolution and a 1 mmHg accuracy. Long-term in vitro and in vivo pressure baseline stabilities of better than 1 and 2 mmHg per month, respectively, have been achieved.
Describes the combination of sensing and circuit technology in monolithic form is making transducers cheaper and more versatile.
Ternary mixtures of water, amine, and complexing agent have been found to etch silicon. The silicon etch rate has been investigated.as
a function of variations in both solution and material parameters. A parallel investigation has been concerned with the etching
characteristics of silicon samples coated with silicon dioxide films. Applications of this etching system to semiconductor
device technology has provided a tool for the chemical shaping of silicon as well as the evaluation of protective surface
films on silicon substrates.
A new solid-state color imager using hydrogenated amorphous silicon(a-Si:H) as a photoconductor, is described. The n-MOS FET scanning array has 485(V) × 384(H) scanning elements, each of which measures 23 µm by 13.5 µm. RF sputtered a-Si:H doped with nitrogen is chosen as the photoconductive material to be deposited on top of this scanner. The transparent electrode of ITO and the filter array of RGB checkered pattern are used to obtain a single-chip 2/3" color imager. The fabricated device has a sensitivity of 40 nA/1×(3200 K) and a saturation current of 1.6 DA. The blooming is suppressed for the highlight exposure(50 % spot) up to 250 times as intense as saturation exposure.
A dielectrically isolated self-aligned silicon gate CMOS process designed for high temperature operation is described. Component characteristics over the 25°C to 325°C range are presented. Circuit operation to 380°C is demonstrated. Circuit and process modifications which could extend operating temperature to about 450°C are suggested.
The formation of thin silicon diaphragms for batch-fabricated pressure sensors is examined. Several anisotropic silicon etchants are compared with respect to their etch rates and the surface finishes produced. Concentrated potassium hydroxide and ethylene diamine-pyrocatechol are found to be most compatible with sensor requirements. Both V-groove and boron etch-stop techniques are capable of controlling diaphragm thickness to within one micron or better, the latter removing wafer taper as a major source of variability. The effects of several process-induced diaphragm irregularities on the pressure sensitivities of piezoresistive and capacitive structures are examined using a finite-difference computer program. Diaphragm thickness is the most important parameter influencing pressure sensitivity in these structures, with resistor-diaphragm alignment and plate separation important secondary parameters in piezoresistive and capacitive devices, respectively.
An electrochemical technique allowing the protection of selected areas of silicon in ethylene diamine-based etchants is reported, and its application to the formation of silicon microstructures is described. Dissolution rates for passivated samples are less than 5 Å/minute, a factor of over 3000 times less than for unpassivated silicon.
The design consideration and performance of an n-p-n structure 484 × 384 element MOS imager is described. The imager has a photodiode array and scanners separately integrated on different p wells. The horizontal scanner, consisting of bootstrapping type noninverting circuits, features high speed and low noise. The maximum scan rate of the scanner is ∼15 MHz. The vertical scanner, consisting of inverting circuits, has a wide dynamic operating range. It can operate stably under an intense illumination of ∼ 1500 1x. Analysis of the MOS switch with a photodiode is also carried out. The 484 × 384 imager has shown excellent performances: signal to fixed-pattern-noise ratio of 54 dB, horizontal resolution of 260 TV lines, vertical resolution of 350 TV lines, well-balanced spectral response, and antiblooming.
A new microminiature monolithic capacitive pressure transducer (CPT I) is 20 times more sensitive than piezoresistive strain-gauge pressure transducers, requires one percent of the power, and can be batch fabricated through current integrated circuit technology. A second device (CPT II) incorporates bipolar signal-processing electronics on the same silicon chip to produce a low-duty-cycle pulse-mode output with period related to pressure. This output format helps to re-solve the problem of shunting between leads, which is one of the principal causes of long-term drift in piezoresistive transducers designed for implantable medical applications. Because this device uses capacitance change as a transductional mechanism rather than piezo-resistivity, it is not susceptible to drift caused by temperature variations in the piezoresistive coefficient. Optimization for totally implantable biomedical applications places special emphasis on small size, high sensitivity, improved long-term baseline stability, and greatly reduced power consumption. These properties are also important for a wide range of pressure-sensing applications-from automotive to general industrial use.
An extremely small batch-fabricatable accelerometer has been developed using silicon IC technology. The device, 3 mm long and weighing 0.02 g, is a simple cantilevered beam and mass structure sealed into a silicon and glass package. The fabrication of the accelerometer is described, and the theory behind its operation developed. Experimental results on sensitivity, frequency response, and linearity are presented and found to agree with theory. The accelerometer is capable of measuring accelerations from 0.001 to 50 g over a 100-Hz bandwidth, while readily implemented geometry changes allow these performance characteristics to be varied over a wide range to meet the needs of differing applications.
A silicon-diaphragm pressure sensor containing on-chip circuitry for signal conditioning has been designed for applications in biomedicine. The device requires no off-chip components and only two external leads, making it suitable for use with multisensor catheters having diameters less than 1.5 mm. The output is a temperature-compensated high-frequency FM analog representation of the applied pressure signal. The device exhibits 1-percent resolution and accuracy over the physiological pressure and temperature ranges. Circuit techniques applicable to a variety of active sensors are descried.
The design consideration and performance of an n-p-n structure 484 X 384 element MOS imager is described. The imager has a photodiode array and scanners separately integrated on different p wells. The horizontal scanner, consisting of bootstrapping type non-inverting circuits, features high speed and low noise. The maximum scan rate of the scanner is ~15 MHz. The vertical scanner, consisting of inverting circuits, has a wide dynamic operating range. It can operate stably under an intense illumination of ~1500 lx. Analysis of the MOS switch with a photodiode is also carried out. The 484 X 384 imager has shown excellent performances: signal to fixed-pattern-noise ratio of 54 dB, horizontal resolution of 260 TV lines, vertical resolution of 350 TV lines, well-balanced spectral response, and antiblooming.
Silicon sensors meet integrated circuits
- Barth
A batch-fabricated silicon accelerometer
- Royland