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The fabrication technology for Si-MEMS devices is mainly derived from the processes used for the realization of microelectronic devices. However, due to the specific demands for MEMS, there are special processes needed for MEMS devices. In this chapter, after reviewing general aspects of microtechnology some of the specific MEMSprocesses will be discussed, e.g. bulk-micromachining, surface micromachining, DRIE and SOI-technology. Keywords: MEMS, microsystem technology, Si-technology, Si-micromachining [ABSTRACT FROM AUTHOR]

Porous Si is formed out of single crystalline silicon in a CMOScompatible electrochemical etch process. This material provides due to its nanoporous structure and high porosity several applications in microsystems/ MEMS. Applications of porous Si are found in optics (luminescence, electroluminescence, Bragg-filters), sensing (humidity, gas sensing), chemical reactions (reformers and fuel cells) and microfabrication (sacrificial layer, 3D structuring). Results of research work in our laboratory are presented together with a review of most relevant results of other groups. Keywords: Porous Silicon, multifunctional material, MEMS, microsystem technology, Si-technology, Si-micromachining, humidity sensor [ABSTRACT FROM AUTHOR]

Nanomaterials such as metal or semiconductor nanoparticles and nanorods exhibit similar dimensions to those of biomolecules, such as proteins (enzymes, antigens, antibodies) or DNA. The integration of the nanoparticles, exhibiting unique electronic, photonic and catalytic properties, with the biomaterials, revealing unique recognition features or catalytic properties, yields novel hybrid nanobiomaterials of synergetic properties and functions. The present review article describes recent advances in the use of biomolecule-nanoparticle (metallic or semiconductive) assemblies for bioanalytical applications. In these systems the unique electronic, photonic, optical and catalytic properties of the nanoparticles are used to transduce the specific biorecognition and biocatalytic functions of the biomaterial components. Keywords: biosensors, biomaterials, nanomaterials, enzyme, antigent, antibodie, nanoparticle, nanorods, DNA [ABSTRACT FROM AUTHOR]

Bulk acoustic wave devices have been developed for the detection and quantification of a large number of compounds. Most of those works do not include an application to real samples and are poor characterized from an analytical chemistry point of view. An overview of the analytical requirements for a real application is reviewed and usual problems frequently faced by the analyst using thickness shear mode devices are presented, as well as some solutions and illustrative practical examples taken from the literature. Keywords: bulk acoustic wave devices, thickness shear mode resonators, quartz crystal microbalance, chemical analysis. [ABSTRACT FROM AUTHOR]

Bimaterial microcantilevers arranged into focal plane arrays (FPAs) can function as uncooled IR imaging devices. In order to analyze the performance of such devices and compare various FPAs, it is essential to have an in-depth understanding of their operation, figures of merit, and fundamental limitations. We give an overview of figures of merit that are applicable to both cooled and uncooled IR detectors. Specific focus of this chapter is a performance analysis for microcantilever IR detectors with an optical readout. We discuss responsivity of microcantilever IR detectors and analyze the different sources (and mechanisms) of noise present in them. A model SiNx microcantilever device with an Al layer in the bimaterial region was fabricated and its performance as an IR detector was analyzed. Keywords: IR detector, thermal detector, focal place array, MEMS, microcantilever, bolometer, uncooled, figures of merit, responsivity, NETD, response time, noise, temperature fluctuation, thermo-mechanical, thermal isolation [ABSTRACT FROM AUTHOR]

The recent developments in micro-mechanical or micro-electro-mechanical (MEMS) systems have enabled the use of new transduction modes that involve mechanical energy and are based primarily on mechanical phenomena. As a result, an innovative family of chemical and biological sensors has emerged. In this work we discuss the recent advances in cantilever transducers. While MEMS represents a diverse family of designs, devices with simple cantilever configurations are especially attractive as transducers for chemical and biological sensors. We discuss four important aspects of cantilever transducers, which include operation principles and models, figures of merit, and applications. We also provide a brief analysis of historical predecessors of the modern cantilever sensors. Keywords: microcantilever, MEMS, micromechanical, resonance, deformation, transducer, stress, chemical sensor, biosensor, analyte, response mechanism, noise, thermomechanical, figures of merit. [ABSTRACT FROM AUTHOR]

The mathematical models and methods for thermal analysis of two typical constructions of microelectronics systems have been presented in this chapter. The 3D thermal model of hybrid circuits in the form of multilayer structure with flat and add-on heat sources have been developed. The combination of numerical and analytical methods for investigation of this model has been used which allows to solve both the steady-state and transient thermal problems simultaneously. The mathematical models of the steady-state and transient heat exchange processes in the flip-chip structures, based on the analytical solution of the conjugate transient heat exchange problem for the die and substrate have been described. The appropriate software in the form of CAD tools have been developed which was tested by solving of several test problems. The estimation of accuracy and efficiency of developed models have been done by comparison with the results obtained by another authors with use of numerical methods. These comparisons show some advantages of analytical approach, namely considerably less computational cost, no influence of discretization errors and possibility to enlarge the sphere of thermal design problems. Keywords: multichip modules, hybrid circuits, flip-chip, thermal resistance, steadystate and transient thermal problems, Fourier series. [ABSTRACT FROM AUTHOR]

This chapter describes the Hall plates with the planar dimensions from micro-meter to deep sub-micrometer range. In the theoretical part, the physical phenomena in such micro-devices are described. Scaling down the dimensions of a Hall plate, the prevailing mechanism of electron transport changes. In macroscopic devices stationary transport takes place. Depending on the device size and applied voltage, the drift velocity of carriers may be linearly dependent on the voltage or saturated. Scaling down further, the device enters the non-stationary transport range, where velocity overshoot and ballistic transport occur. In each regime magnetic sensitivity and noise of the device are estimated. In the experimental part, a review of the published results on the technologies, performance, and applications of micro-Hall devices is given. In summary, scaling down a Hall sensor brings about a degradation of its basic characteristics. On the other hand, micro-Hall devices open the way to applications where high spatial resolution is necessary, like in scanning Hall probe microscopy. Keywords: Magnetic sensors, micro-Hall, scaling down, sensitivity, noise, resolution. [ABSTRACT FROM AUTHOR]

Precise magnetic sensors are required in many fields: besides the traditional geophysical magnetometers they serve for navigation, position tracking, military and security. First a short review of basic practical rules and sensor parameters is given. Next the most important semiconductor magnetic sensors (Hall sensors and semiconductor magnetoresistors) are discussed. Following sections describe the most important precise magnetic sensors: ferromagnetic magnetoresistors (AMR, GMR and SDT) and fluxgate sensors. Other types of magnetic sensors (SQUIDS, Magnetooptic sensors, GMI and Magnetostrictive sensors) are described briefly. Section 6 is devoted to current sensors based on magnetic principles: Instrument current transformers, Rogowski coil (di/dt sensor), Fluxgate DC current sensors, Hall current sensors, and Magnetoresistive current sensor. Other applications of magnetic sensors are reviewed in Section 7. They include position sensors, Compass, Security and military applications, Geophysics and Space research, Biomagnetism and medical applications, and Non-destructive testing. Final section compares the described sensor types. Fluxgates are the most precise vectorial sensors, followed by AMRs, which become great competitors of Hall sensors. Until now, GMR and SDT sensors are rather nonlinear. GMI sensors are recently commercially available, but their present accuracy is not competitive. Common problem of magnetic sensors containing ferromagnetic material is perming (remanence). This was solved only with fluxgates and flipped AMRs. Keywords: vectorial magnetic sensors, magnetoresistors, fluxgate sensors, Hall sensors, magnetooptic sensors [ABSTRACT FROM AUTHOR]

Surface acoustic wave (SAW) devices can be turned into identification and sensor elements, so called SAW transponders. Identification elements transmit an individual ID number and sensor elements measure physical quantities such as temperature, pressure, torque, acceleration, humidity, etc. The SAW devices do not require any power supply and may be accessed wirelessly. The complete sensor system consists of such a SAW transponder and a local radar transceiver (reader unit). An RF burst transmitted by the radar transceiver is received by antenna of the passive SAW transponder. The passive transponder responses with an RF signal, like a radar echo, which can be received by the front-end of the local transceiver. Amplitude, frequency, phase and time of arrival of this RF response signal transmit information about the SAW reflection and propagation mechanisms which in many cases can be directly attributed to the sensor effect for a certain measurement value. Due to the high delay time of the SAW transponder in the order of a few microseconds, usually no intersymbol interferences due to environmental reflections occur when the system operates in harsh indoor/outdoor environments. This chapter first surveys about classical wired SAW sensors. Then the functional principles of such wireless SAW transponder systems and the reader systems will be pointed out. Furthermore the design requirements for SAW transponders, such as identification tags and radio sensors, several application examples and their state-of-the-art performances are presented. Keywords: Passive SAW transponder, surface acoustic wave, local radar transceiver, wireless measurement, sensor, identification, temperature, pressure, torque, acceleration, tire-road friction, magnetic field, water content of soil [ABSTRACT FROM AUTHOR]

The operating principles, design and manufacturing in thick-film technology (TFT) of sensors based on the piezoelectric and pyroelectric properties of lead zirconate titanate (PZT) thick films are described. In particular, the attention is focused on acoustic-wave piezoelectric sensors for physical and chemical quantities, and on pyroelectric sensors and arrays for light spot position measurement. Keywords: piezoelectric sensor, pyroelectric sensor, acoustic-wave sensor, sensor array, thick-film technology, lead zirconate titanate (PZT). [ABSTRACT FROM AUTHOR]

Acoustic wave devices based on piezoelectric crystals and used for materials characterization and biochemical sensor applications are covered. The various acoustic wave devices used for physical and biochemical sensing applications are briefly described. Two types of sensors under development are discussed in details. They are the thickness shear mode (TSM) resonators and the guided shear horizontal surface acoustic (guided SH-SAW) devices, also commonly known as Love wave devices. It is noted that the two types of devices can be used for sensing in gas and/or liquid phase. The effectiveness of the TSM resonator for polymer material characterization is presented and discussed. The impedance-admittance characteristics of the equivalent circuit models of both the unperturbed and coated resonators are analyzed to extract the polymer storage modulus and loss modulus (G' and G''). The design and performance of guided shear horizontal surface acoustic wave (guided SH-SAW) devices being investigated and under development for high sensitivity chemical and biochemical sensors in liquids are discussed. It is noted that despite their structural similarity to Rayleigh SAW, SH-SAWs often propagate slightly deeper within the substrate, hence preventing the implementation of high sensitivity detectors. The device sensitivity to mass and viscoelastic loading can be increased using a thin dielectric guiding layer on the device surface. Suitable design principles for these sensor platforms are discussed with regard to wave guidance, electrical passivation of the interdigital transducers (IDT) from the liquid environments, acoustic loss, and sensor signal distortion. Results of chemical sensing and biosensing experiments are presented and discussed. Keywords: resonant piezoelectric device, biochemical sensor, TSM resonator, guided SH-SAW device, polymer material characterization, acoustic wave device. [ABSTRACT FROM AUTHOR]

The chapter discusses classical (standard counting technique, indirect, interpolation and combined counting methods) and advanced (suitable for self-adaptive smart sensors) methods for frequency (period)-to-code conversion: reciprocal, ratiometric, constant elapsed time (CET), M/T, single (SB) and double buffered (DB), direct memory access (DMA), self-adapting methods of dependent count (MCD) and method with nonredundant reference frequency and methods for duty-cycle - to - digital and phase-shift - to - digital conversion. The comparative analysis is given. Keywords: frequency-to digital conversion methods; duty-cycle - to - digital conversion methods; phase-shift - to - digital conversion methods; method of dependent count (MDC); method with non-redundant reference frequency. [ABSTRACT FROM AUTHOR]

The chapter gives an overview of industrial types of smart sensors (temperature, pressure, rotation speed, optical, humidity, gas, chemical, acceleration, biosensors etc.) and contains quasi-digital, smart sensors and MEMS definitions. Digital and quasi-digital (frequency and dutycycle output) sensors and transducers are considered. The obvious tendency of sensors accuracy increasing up to 0.01 % or better and wide conversion frequency range from several hundredth parts of Hz up to several MHz are observed. Main advantages of frequency-time domain signal as informative parameters for modern smart sensors are described. Keywords: smart sensor; MEMS; frequency-time domain; digital sensor; quasidigital sensor; transducer; integrated sensor; intelligent sensor; parametric sensor; self-generating sensor; modulating sensor, biosensor [ABSTRACT FROM AUTHOR]