Plasma etching has been used for the fabrication of micromechanical structures in silicon with fine feature size. In this paper, reactive ion etching (RIE) is used for micromachining applications in two steps, first for etching of SiO₂ layer and then machining of silicon. The first RIE step is for the patterning of the SiO₂ layer using photo-resist as mask. This process involves the use of gas mixture of CHF₃ and Ar. The photo-resist is then removed in the oxygen plasma. The second step is to delineate the patterned SiO₂ layer onto the silicon wafer using SF₆/O₂ plasma. The oxygen flow is varied from 2-10 sccm in SF₆. Silicon etch rates of 195 nm/min and Si/SiO₂ selectivity of 10:1 has been obtained. The process parameters such as gas flow, rf-power and etch pressure are optimized as per our reactor's configuration to have compromise for best selectivity, anisotropy, and high etch rates. A pattern transfer with nearly vertical walls is obtained for RIE based on SF₆/O₂/CHF₃ while maintaining the substrate at low temperature.

A comparatively new micromechanical machining process, semi- magnetic abrasive machining which uses magnetic force as a machining pressure has been developed in ISRO/IIT recently for the precision finishing of cylindrical components. The process is controllable because the machining pressure is controlled by the current that is input to the coil of solenoid, but it needs the monitoring of the surface roughness by controlling the process parameters. For this the surface roughness is predicted as a function of input parameters like rotational sped, magnetic flux density, abrasive grain size, machining duration, and clearance between the workpiece and the poles by a model that has been derived from the removed volume of material. The simulation results are confirmed by comparing them with the experimental results.

Today's advanced IC fabrication techniques have let silicon micromachined into the tiniest electromechanical systems ever built. In just ten years, MEMS has blossomed into a vital industry with numerous practical applications. Semiconductor Complex Ltd., the nation's leading VLSI company has developed CMOS technologies which are in tune with the MEMS fabrication process.

We have designed, fabricated and tested a balanced doubly suspended versatile, torsion and flexural, MEMS resonator structure. The doubly suspended structure has been used earlier for very precise high Q resonators but we wished to study the various vibration modes of such a structure. FEM analysis has been used to compute the most likely 6 modes and their frequencies of free vibration. These modes include flexure, torsion and mixed modes. The arms of the resonator are deposited with magnetic films so as to give desired bending/twisting moments to the structure. The location of the films decides the symmetry and thus result in one of the six vibrational modes that are predicted by the FEM analysis. This paper describes the design, fabrication and measurements on resonator structures made at TIFR.

TRIZ is a Russian abbreviation. Genrich Altshuller developed it fifty years ago in the former Soviet Union. He examined thousands of inventions made in different technological systems and formulated a 'Theory of Inventive problem solving' (TRIZ). Altshuller's research of over fifty years on Creativity and Inventive Problem Solving has led to many different classifications, methods and tools of invention. Some of these are, Contradictions table, Level of inventions, Patterns in evolution of technological systems, ARIZ-Algorithm for Inventive Problem Solving, Diagnostic problem solving and Anticipatory Failure Determination. MEMS research consists of conceptual design, process technology and including of various Mechanical, ELectrical, Thermal, Magnetic, Acoustic and other effects. MEMS system s are now rapidly growing in complexity. Each system will thus follow one or more 'patterns of evolution' as given by Altshuller. This paper attempts to indicate how various TRIZ tools can be used in MEMS research activities.

A sensor's frequency response range and its sensitivity mainly depend on the stiffness and the natural frequency distribution of the sensing structure. Both the parameters, stiffness and naturally frequency distribution, can be changed by varying the geometric configuration of the sensing structure. This paper present a frequency shift analysis of a typical microstructure used in MEMS. The frequency shift analysis is carried out by changing the geometric configuration of the structure and obtaining the frequency band for different configurations. This work provides a tool to understand the effect of geometric configuration on microsensors characteristics.

The action spectrum for light-induced damage to the retina results from wavelength dependent transmission of the pre-retinal ocular media, wavelength dependent absorption in retinal chromophores, and chromatic aberration of the eye optics. While various light/tissue interaction mechanisms have been implicated, thermal mechanisms dominate in the red and near-infrared for all exposure durations and in the visible for exposures shorter than a few seconds. A number of investigators have measured the transmission of the eye and the spectra of retinal absorbers, and thermal models based on these data predict the broad features of the action spectrum. Dose/response studies with lasers conducted over the past 40 years have mainly validated the thermal models. However, thresholds for laser induced chorioretinal injury using q-switched pulses show a variability ofthreshold with small changes in wavelength

High Resolution X-ray diffractometry and topography techniques have been employed successfully to evalute crystalline quality and long term stability of coiled membranes. The process of membrane fabrication involved photolithography, implantation by 4 MeV N⁺⁺ ions in n-type GaAs substrates followed by selective etching. A five crystal x-ray diffractometer was employed in setting with MoK(alpha) ₁ exploring beam for x-ray diffraction experiments. Exploring beam width was reduced to approximately 10 micrometers to selectively illuminate different segments of the membrane. Diffraction curves recorded from the bulk crystal surrounding the sensor were quite sharp with half widths in the range: approximately 15-26 arc sec, where as the diffraction curves from sensor segments were quite broad due to appreciable deformations. The sensor segments were tilted with respect to each other as well as with respect to the substrate. High resolution x-ray diffraction topographs directly revealed that the sides of the cavity were not vertical, but tapered, there is a thin freely hanging strip over the tapered regions due to under- etching and the bottom of the cavity is uneven with perturbations in the range: +/- 4 micrometers .

A MEMS vibration detector fabricated at the Solid State PHysics Laboratory, Delhi, has been analyzed for its mechanical response. The sensor consists of a central plate mounted on webs. Change of capacitance between the central plate and the base is used to measure the vibration. This paper describes analysis of the mechanical characteristics of the device.

The electrical resistivity measurement on ZrS_0.5Se_1.5 has shown a metallic behavior in the range 333-363 K followed immediately by metal-semiconductor transition. It is verified using percolation model and Mott-Hamilton- Pollack relation that this particular composition of zirconium sulphoselenides is 3D. Details show a sine wave potential which is indicative of the prevalence of charge density wave. Umpklapp processes are found to dominate giving rise to T⁶ power law for resistivity in the metallic range.

On the base of microelectronical and micromechanical technology were designed and developed converters of hydrogen concentration to electrical signals. The devices of controlling concentration of hydrogen in the air were developed. These devices were applied for ensuring fire and explosion security of complex technological teste of missile oxygen-hydrogen engine, developed for cryogenic accelerations block. The sensor block of such device was installed directly on the armor-plate, to which was attached tested engine.

On the base of silicon semiconductor and membrane technology was developed and produced a methane-control sensor, which is notable for small energy consumption and high speed. As a functional element was used a catalytic layer, which is a chemically deposited platinum and/or palladium, on the nanostructural silicon. With on the framework of this project, a mechanism of chemical deposition of platinum and palladium on the porous silicon was investigated. On the base of IR-spectrography results, ASM-microscopy of developed structures and thermodynamical analysis was observed the ultimate role of surface protonation of porous silicon in the process of metal deposition. Testing of developed sensor has shown that functional layer on the base of metalized porous silicon is not inferior according to its catalytic properties of platinum or palladium.

Liquid crystals (LC) are well known as smart material that changes its properties under the influence of external influence. Usually they used to visualize the distribution of not uniform thermal, electrical, magnetic, acoustic fields or for chemical and radiation detection. In this paper a new unique application of LC for surface tension mapping of solid surfaces is described.

New impressive heavy metal detection limits at analysis of high pure materials and environment samples have been obtained with a laser excited atomic fluorescence spectrometer. A resonant multistep ionization spectrometer with laser ionization in capillar of atoms with radioactive nuclei is used as a chemically selective laser ion source in experiments for obtaining isobarless isotope beams and their applications in problems of new materials research, astrophysics and nuclear physics. A laser photoelectron projection spectromicroscope is developed for photoelectron image detection of single absorbing centers on a surface with an atomic-molecular spatial resolution. A number of portable spectral instruments including based on new principles has been developed for using in these laser installations and for other applications.

New microcomponent constructions and fabrication method have been proposed and developed. This new approach is based on fiberglass technology. The outstanding opportunities of this technology have been demonstrated and used for fabrication of submicrometer x-ray mask; synchronous micrometer containing permanent magnet; microcoil with 7 micrometer lines. Our technology gives an opportunity for fabrication of the structures with extremely high aspect ratio, spiral- like conductor and so on. Developed technology does not use expensive x-ray lithography. Possible application of developed technology for production different microcomponents for electron and x-ray optics components, MEMS and other devices have been discussed.

The classical microelectromechanics is oriented to the standard silicon technology which is presently dominated by the 'silicon-on-silicon dioxide' structure. This choice presents a combination of two wide band gap materials: one is aluminum nitride which is a pronounced dielectric and possesses piezoelectric properties as well, and the other, silicon carbide, is a typical semiconductor. Both of them are optically active, including the UV region, and have high heat conductances and Debye temperatures which are characteristic of the material durability against thermal, chemical and radiation influences.

Scientific and Manufacturing Complex 'Technological Center' (SMC TC) was founded in the Moscow Institute of Electronic Technology in 1988. In 1989 in 'Technological Centers' a set of technological and analytical equipment for treatment of silicon wafers of 100 mm of diameter and manufacturing of photomask was put into operation. In 1990 the first integrated circuits were made on CMOS technology. Since 1994 the research and works out int he area of microsensors' and microsystems' technologies have been conducted.

Vibration sensors are an integral part of many microelectromechanical systems (MEMS). Excellent electronic and mechanical properties of Silicon make it the perfect material for developing these sensor. MEMS technology is mainly based on silicon micromachining. A vibration sensor has been developed using bulk micromachining of silicon. The key element here is the suspended seismic mass which forms a spring mass system. Movement of the seismic mass in the presence of vibration is monitored to sensor and control vibration. Various aspects dealing with the development of these devices are discussed in this paper.

Accelerometers are key components of various motion control systems ranging in use from inertial guidance of rockets and satellite launch vehicles to safety applications in the automotive industry. The accelerometers that are used for spare inertial systems are characterized by high resolution, small bandwidth, large working range and excellent linearity. Current advances in this field are based on silicon micromachining. Silicon bulk and surface micromachined accelerometers offer advantages of reduced size and weight, less power consumption and the use of a fabrication process derived form an already well established semiconductor fab technology. Of the various approaches to silicon micromachined accelerometers, two are in a well advanced state of development. The first is the capacitive force balanced type and the second the piezoresistive type. The capacitive approach has the advantage of higher stability and resolution and lower temperature coefficients. But it requires proximal detection circuitry to prevent parasitics to overwhelm the circuit. A new approach reported recently uses a silicon micromachined cantilever beam which acts as a Fabry Perot interferometer when light form an optical fiber is impinged on it. In this paper we overview all the approaches and try to select a suitable candidate for use in space borne inertial systems.

Hall sensors place themselves in important position, in the fields right form scientific and research to the industrial and related applications. Various materials e.g. InSb, InAs, Si are reported for use even in commercially available Hall sensors. The use of Si, not only makes it possible to apply the highly developed and sophisticated batch production methods of integrated circuits to transducer field, but also makes it feasible to integrate sensor and signal processing circuits on a single chip.

Polymer thin film devices are fast emerging as efficient active elements for processing of optical signals for using civil, space and military applications. The requirements for a thin film material to be used in optical processing and communication are the high second and third order non-linear susceptibilities, low propagation loss and variable depth, propagation to allow the same device operate at different wavelength.

Polymers are the new and fast emerging materials with a growing scientific and technological interest. The material, though of recent origin, offers unique possibility of tailoring their properties to suit a large variety of applications. The properties and characteristics of intrinsically conducting polymers make them suitable materials for several applications. The detectors made with such organic polymers can help in quick and easy identification of the microbes.

Anisotropic etching using alkaline solution has been adopted to form trenches in silicon while fabricating surface oriented bulk window SPST switches. An array pattern has been etched on silicon with good control on depth of trenches. KOH-water solution is seen to yield a poor surface finish. Use of too much of additive like isopropyl alcohol improves the surface condition but distorts the array pattern due to loss of anisotropy. However, controlled use of this additive during the last phase of trench etching is found to produce trenched arrays with desired depth, improved surface finish and minimum distortion of lateral dimensions.

Uncooled thermal IR arrays have attracted a great deal of interest due to its large number of applications in military as well as in civilian sector. These systems contain microbolometers, which can be made using silicon micromachining technology. An integrated approach is also needed to design the complete system by developing the large number of IR sensing elements, electronics, optics and housing. This paper discusses the design approach and technology used her to develop the IR-sensing microbolometers. The most significant achievement is the perfection of the sacrificial layer to obtain 1.0 micrometers air gap between the oxide diaphragm and the silicon substrate. This provides a very good thermal isolation required to obtain the high sensitivity for the IR sensing. Silicon dioxide diaphragms of 0.3 micrometers thickness and of 375 micrometers X 275 micrometers sizes have been made with 1.0 micrometers air gap from the silicon substrate. This is supported by four hinges. Technology has also been perfected here to make 30 mm X 30 mm diaphragms of 1.0 micrometers thickness with the same air gap. Four layer structures have been grown on this diaphragm by evaporation and structured to form titanium microbolometers using many steps of photolithography. These microbolometers are made of 1000 A thick Ti with gold contacts. The surface has been passivated by SiO₂ layer to maintain the characteristics of the Ti-bolometer stable and reproducible. The temperature coefficient of resistance (TCR) of Ti - bolometers has been measured and found 0.23 percent per degree centigrade. The value of TCR decreases with the reduction in the thickness of Ti of the bolometer. A 20 element array has been made using this technology.

This paper presents design of an hybrid micromachined silicon - fiber optic pressure sensor array for tactile sensing applications. Tactile sensing is basically related to identify the surface texture through pressure/strain distribution over a sensor matrix. Silicon micromachining technology has shown the capabilities of producing structures like diaphragms, cantilevers and precise holes. With anisotropic etching and techniques like boron stop these structures can be designed to desired precision. Conventionally, techniques like deposited or doped piezoresistors on the diaphragms or cantilevers are used for pressure/strain sensing. These, however, require support of sophisticated external signal conditioning.

There have been several cantilever-based actuators which provide movement in a direction transverse to the length of the cantilever. Here we describe a novel actuator which gives movement in the same direction as that of the length of the element. This is achieved by a curling up action of a bimetal like 'metal on silicon dioxide' straight element due to large differences in the coefficients of linear expansions and the high temperature which is obtained during the metal deposition.

The magnetoelectric (ME) materials exhibit ferroelectric/ferrielectric/antiferroelectric properties in combination with ferromagnetic/ferrimagnetic/antiferromagnetic properties. Under the action of external magnetic field, such materials would show electric polarizations, while the external electric field would induce magnetization. In most of the known ME materials measurable output was recorded at very low temperatures. However, for practical applications it is desirable to synthesize new ME materials which undergo dielectric and magnetic transitions above room temperature and exhibit enhanced ME output.

In this paper, we report the observation of the effect of magnetic field on the shift of resonant frequencies of a composite consisting of 40 percent PZT and 60 percent Ni_0.98Co_0.02Fe₂O₄. The samples were synthesized by sintering a compressed mixture of Ni_0.98Co_0.02Fe₂O₄ and the PZT at 1200 degrees C. The samples were electrically poled at 7.5 kV/cm for 30 mts at 100 degrees C and were cooled to room temperature in the presence of filed. The resonant frequencies were determined by analyzing the admittance plots. The electromechanical coupling coefficients were evaluated by the resonance- antiresonance method. The results show that there is a considerable shift in resonant frequency under the action of magnetic field. The relative shift in the resonant frequency in crease with increasing field, reaching a maximum around 1.5 kOe.

This paper discusses the various aspects of PANI-ABS composite and its suitability as a chemical sensor material for aqueous ammonia followed by a change in the resistance value. The response of polyaniline-ABS composite film was studied for aqueous ammonia from 0.001N to 1.0N concentrations. Both FTIR and UV-visible spectroscopic studies reveal that PANI-ABS composite film s can be used as a chemical sensor particularly with reference to aqueous ammonia.

Over the years significant advances have occurred in the development of materials which possess smart or intelligent functions of the material. Recent trends in research imply that technology is to mimic or emulate human beings. These materials contain their own sensors, actuators and control capabilities, responses to its environments, in a timely manner are popularly known as smart/intelligent materials. Smart structures can be defined as materials that possess at least one smart component within itself. Few examples of smart materials usage are piezo-ceramic sensor in vibration control, SMA actuators, like wise other smart materials applications are product health monitoring, cure monitoring, intelligent processing, active and passive control and so on. Existing smart materials/structures are mainly macroscopic in nature i.e., predominantly embedded or surface mounted sensors and actuators operating synergistically at molecular level for tailored applications.

New requirement for communication, computing, optoelectronics, medical, space, civil and military systems stress the need for increasing sped, information content and processing of optical energy in specific forms. In order to meet the requirements the device technology must be improvised. The development of new lasers has satisfied the source requirements. New low coast and efficient optoelectronic devices are desirable to process and detect the light derived from such sources, so that the optical system becomes capable of high speed functioning, rapid information density communications and computing. The current available are the devices made from single crystals, epitaxial films and thin films of Si HgCdTe and ZnTe, ZnSe, ZnTeSe and Cd_1-xZn_xTe.

Polymer systems which undergo changes in volume with change in temperature, solvent or any other external stimuli find application in medicine, biotechnology and Industry. The changes which are observed are reversible and do not show any hesterisis over number of times, the experiments are repeated. The pH of systems are important in biochemical reactions and in industrial chemical reactions. Polymeric intelligent systems that can show a change in light transmission over a wide pH range can be devised to develop light induced switches to monitor the program of reaction, addition of ingredients and also control other related factors such as temperature. Such close control chemical reactions are often desired where addition/substitution of ingredients in responsible for one type of spatial order.

Starting from the very definition of smart structures and smart materials, this paper addresses the fundamental mechanism of operation of some well known smart materials like piezoelectric ceramic/polymer, electrostrictive ceramic, magnetostrictive alloy, shape memory alloy, electroheological fluid, magnetoheological fluid, optical fibers and so on. It also describes briefly the working principles of the actuators and sensor based upon these materials. In addition to that an overview of the various applications and research dealing with the application of these smart materials in aerospace structures mainly in the context of vibration suppression, shape control and adaptive structures for their efficient functioning has been presented. On the whole the presentation stresses on actuators. Since it is the actuator not the sensor that is often the limiting factor in smart structure used for active control. Numerous investigations have been made and are on the way to improve upon the piezoelectric and electrostrictive actuator for greater generating force and larger stroke, as well as shape memory alloy actuator for fast response. Development of multilayer piezoelectric and electrostrictive actuator and discovery of precompressed piezoelectric element and actuator is a forward leap in that direction.