We have constructed a humidity-controlled chamber in which deflections of polysilicon cantilever beams are observed by interferometry, resulting in in-situ adhesion measurements within a fracture mechanics framework. From adhesion energy measurements for uncoated hydrophilic beams, we demonstrate an exponential dependence of adhesion on relative humidity (RH). We can explain this trend with a single-asperity model for capillary condensation. For coated hydrophobic beams, adhesion is independent of RH up to a threshold value which depends on the coating used. However, we have found that exposure to very high RH (greater than or equal to 90%) ambients can cause a dramatic increase in adhesion, surprisingly with a stronger effect for perfluorodecyltrichlorosilane (FDTS, C₁₀H₄F₁₇SiCl₃) than octadeycltrichlorosilane (ODTS, C₁₈H₃₇SiCl₃). Newly developed computational mechanics to measure adhesion in the presence of an applied load allow us to explore how the adhesion increase develops. We believe that water adsorption at silanol sites at the FDTS/substrate interface, possibly exacerbated by coupling agent migration, leads to water islanding and the subsequent adhesion increase at very high RH levels.

Development of a surface micromachining process for commercial scale production of absolute pressure sensors necessitates the definition of inspection tests at each stage of the process and for the completed packaged product. The yield measurement described in this paper is for a Field Effect Transistor pressure sensor integrated into a CMOS process. This measurement can be divided into verification of the electrical and mechanical properties of the pressure device. This paper describes the development of a simple method for mechanical yield determination. The method is based on a visual inspection procedure where the interference rings observed under a conventional 5X/20X inspection microscope, are correlated with white light interferometry (wafer level and packaged devices) and Atomic Force Microscopy (AFM) (wafer level) measurements. The application of these two profiling methods is also compared in the paper. Based on this work a simple, low cost, automatic system for yield determination using standard equipment can be developed. Initial results from a software system for inspection automation are presented.

Heat transfer mechanisms in electrostatically actuated torsion mirrors are dominated by heat conduction in the torsion springs and the air gap between mirror plate and driving electrodes and by convection above the mirror. The maximum optical power rate capability of micromirrors strongly depends on the reflectivity of the mirror surface and of the heat transfer out of the mirror plate. The results provide important knowledge since increased mirror temperature influences its optical parameters like flatness and roughness, the dynamical system behavior or even damages the reflective layer. This paper deals with investigations of the heat transfer by conduction and convection. The cumulative heat resistance of micromirrors is calculated using analytical formulas and by means of finite element modeling. Theoretical results are compared with experimental data. A thermographic imaging system and electrical heating is used to measure the thermal decay function which evaluates the resistance at known capacitance. It can be deduced that an optical power of several Watt can be steered by micromirrors.

In this study, three novel optical sensors are described. They are the pinhole integrated with the surrounding photodiode, the transmission type position sensor fabricated on the Si mesh structure, and the photodiode thinner than the optical wave length in the active layer. These sensors have unique optical functions as well as photodetection. These devices offer new concepts and easy construction of the optical systems to realize applications, which have been complicated or laborious in the conventional way. They are automatic alignment of the pinhole, detecting many points along a straight line, and detecting the intensity profile of the interference of the standing wave respectively. Each sensor absorbs only a part of the incident light beam and the rest passes through the sensor and enables to detect the information of the incident light beam not disturbing the optical field very much. The almost light beam continues to propagate to the down stream, and the transmitted beam can be used for the further function.

This paper presents the design and the fabrication steps of a novel integrated Mach-Zehnder interferometer with a phase modulation. A well-controlled Si machining as well as ZnO thin-film transducer integration on the same Silicon substrate permits to transform an optically passive device to an active device with sinusoidal phase modulation of 1.3 rad.

The mechanism of direct bonding at room temperature has been attributed to the short range inter-molecular and inter-atomic attraction forces, such as Van der Waals forces. Consequently, the wafer surface smoothness becomes one of the most critical parameters in this process. High surface roughness will result in small real area of contact, and therefore yield voids in the bonding interface. Usually, the root mean square roughness (RMS) or the mean roughness (Ra) are used as parameters to evaluate the wafer bondability. It was found from experience that for a bondable wafer surface the mean roughness must be in the subnanometer range, preferentially less than 0.5 nm. When the surface roughness exceeds a critical value, the wafers will not bond at all. However RMS and Ra were found to be not sufficient for evaluating the wafer bondability. Hence one tried to relate wafer bonding to the spatial spectrum of the wafer surface profile and indeed some empirical relations that have been found. The first, who proposed a theory on the problem of the closing gaps between contacted wafers was Stengl. This gap-closing theory was then further developed by Tong and Gosele. The elastomechanics theory was used to study the balance between the decrease of surface energy due to the bonding and the increase of elastic energy due to the distortion of the wafer. They considered the worst case by assuming that both wafers have a waviness, with a wavelength (lambda) and a height amplitude h, resulting in a gap height of 2h in a head to head position. This theory is simple and can be used in practice, for studying the formation of the voids, or for constructing design rules for the bonding of deliberately structured wafers. But it is insufficient to know what is the real area of contact in the wafer interface after contact at room temperature because the wafer surface always possesses a random distribution of the surface topography. Therefore Gui developed a continuous model on the influence of the surface roughness to wafer bonding, that is based on a statistical surface roughness model Pandraud demonstrated experimentally that direct bonding between processed glass wafers is possible. This result cannot be explained by considering the RMS value of the surfaces only, because the wafers used show a RMS value larger than 1 nm. Based on the approach exposed in reference six, a rigorous analysis of wafer bonding of these processed glass wafers is presented. We will discuss the relation between the bonding process and different waveguide technologies used for implementing optical waveguides into one or both glass wafers, and give examples of optical devices benefiting from such a bonding process.

More and more technologies and new materials have been combined with silicon process technologies to enhance the performances of microsystems and extend the application fields. Among these technologies, the Shape Memory Alloys (SMA's) as thin films have been developed recently. They have been shown to induce high displacement and large force/mass ratio under low voltage. They can produce work output higher than can be provided with other kinds of actuators. However, such SMA actuators are not easy to make because specific annealing treatments or mechanical bias springs are needed to realize cyclic device operation. Moreover, adhesion problems of SMA thin films may occur during the annealing treatment. We have developed a simple fabrication process allowing a reliable operation principle of a micromembrane. The cyclic actuation is ensured by membrane thickness residual stresses that avoids the assembling steps. These membranes whose surface varies from 200 X 200 micrometer² up to 2 X 2 mm² have been successfully tested. As developed, they are very adapted to integration process of microelectronics and can be applied to many applications such as optical, fluidic devices, and especially for biomedical applications as SMA's are biocompatible.

Investigation of the vibrational behavior under operating conditions are often necessary for realization and inspection of sensor and actuator functions even to assure of there high reliability. Also the behavior under separate excitations is important to know especially for applications of sensors and actuators into vibrating environments. Relating to this exceptionally high demands are exemplary required for aviation, automotive industries, and mechanical engineering. The paper describes the coupling of a Single-Point Laser Vibrometer with a Modal Analysis System. Beside detection of eigenfrequencies a contactless determination of mode shapes is possible too. For vibrational characterization of scanning micromirrors were to investigate both the vibrational behavior under operating conditions and under separate excitation. Gradual improvements to develop an appropriate test stand for vibration measurements at these microstructures are represented. Also measurements taken with Laserscanning Vibrometry and Holographic Interferometry are discussed. Results of Laseroptical Modal Analysis could serve as foundation for calculations and numerical simulations.

In this paper investigations of temperature control of micro channel cooled high power diode lasers are presented. After a short motivation the theoretical background of a complete liquid cooling system is introduced and the simulation results are compared to the behavior of a real-world system. Because of the nonlinear dependence of the thermal resistance on the water flux modern control algorithms are required to achieve a sufficient control quality and robustness. Their design and characterization are presented as well. Based on the results of diode laser temperature control the potentials to realize a highly efficient wavelength control are discussed. To support future system integration and to realize the controller with minimal hardware expenditure an application specific integrated circuit (ASIC) was developed.

The automatic inspection of cracks in the inner side of steam generator tubes is routinely carried out using eddy currents techniques. These methods are mature and have quite high performance but the achievable resolution is relatively low (approximately 1 mm) and present drawbacks related to the reliability of the inspection of the areas of tubes at the neighborhood of the supporting plates. Several years ago we have proposed a solution to these limitations based on a new fiberoptic reflectometric technique that has already been theoretically and experimentally analyzed using a first laboratory prototype. In this work we describe a second generation prototype that is integrated in a whole inspection system that could perform an inspection in the field. The results obtained over cylindrical tubes with inner diameter 16.8 mm (corresponding to real steam generator tubes) with cracks created by electrical disintegration and by stress- corrosion and employing conditions close to real operation confirm our previous conclusions: both circumferential and axial cracks of widths as small as 30 micrometer can be detected and measured and typical resolution capability of 10 line pairs/mm can be obtained.

Novel optical and optoelectronic technologies make it possible to provide real-time, highly precise metrological tools for microsystems fabrication. Custom light sources with unprecedented efficiency, polymer replication of micro-optical components, optical monoblocks of glass or polymers comprising many optical functions, assembly techniques adopted from microelectronics and smart CMOS photosensors are the basis of this development. It is illustrated with three practical examples: (1) An absolute, high-precision, low-cost optical encoder, (2) low-noise, low-power and high-speed minicameras, and (3) real-time range imaging with micron resolution based on low-coherence optical tomography.

The aim of this project is to develop the smallest and most sophisticated wireless fully autonomous instrumented robot capable of subatomic movements. The robot named 'NanoWalker' should bring a new paradigm in the way instruments are built while providing a sophisticated platform for a new range of applications. The project involves primarily the investigation of a new legged locomotion based on piezo-actuators with advanced micro-assembly techniques applied to complex embedded electronic systems; the development of new miniature instruments, micro-manipulators, integrated behavior for controlling, searching and scanning at the atomic scale; and the development of a subatomic navigation system. Besides all the new technologies and techniques that we intend to develop and which will be applicable to many areas and systems, the NanoWalker should provide a suitable yet more flexible and powerful platform compared to traditional macro-scaled instruments. It is anticipated that this new form of highly integrated autonomous microsystem will be used as the main building block for a new generation of measurement and inspection systems. In this paper, the main components of the NanoWalker are briefly described.

In this paper microscopic interferometry is used for 2D and 3D profiling of micromechanical devices deformation and, is extended to allow vibration spectra measurements on a few microns wide microdevices. This is obtained by adding an apertured photomultiplier with suitable signal processing and subnanometric piezoelectric excitation. Resonant frequencies are detected both from vibrations-induced fringes contrast variations and by using a homemade wide bandwidth (10 MHz) double lock-in amplifier. This allows vibration measurements up to several MHz with a spatial resolution down to 1.25 micrometer and a detection limit of vibrations amplitudes in the 0.2 - 1 nm range. Furthermore the system allows a direct visualization of the whole vibration modes and can be applied for automated bulge testing of membranes. System operation for 3D profilometry, vibrometry and bulge testing is demonstrated on Cr cantilever microbeams and microbridges fabricated by surface micromachining and on membranes. Capabilities of the system for large vibration amplitudes measurements and its extension for on-wafer resonant frequencies measurements by using optical excitation are discussed.

Shading masks consisting of regular grids of thin metallic wires have been used for the vacuum deposition of micro- optical thin film components. The fabrication of cylindrical microlenses with single- and two-step procedures has been demonstrated. Refractive as well as partially reflective arrays with pitches greater than or equal to 50 micrometer have been realized with SiO₂ and SiO₂:HfO₂ layers on glass, quartz and polymer substrates. The thickness profiles have been characterized interferometrically.

Hybrid microsystems with optical and mechanical functions can be implemented economically only by an automated assembly. In order to guarantee a high quality of the products, the use of a flexible and simply manageable process control system is necessary. The Laser-Scanning-Microscopy, based on the confocal microscopy, is suitable due to the variable magnification and the threedimensionally visualization ideally for the automated micro-assembly. The confocal Laser-Scanning- Microscope (CLSM) serves in fabrication and also in assembly apart from the process visualization for the analyze for micro surface structures, the detection of defects or the measurement of threedimensional geometries of microparts.

The growing development of modern microcomponents, structures and systems, makes it necessary to qualify large-scale approved measurement methods for the investigation in micro- scales. New materials and structural design are employed whose behavior cannot be easily predicted by FE-methods. Material properties and boundary conditions which are known form large- scale investigations may differ considerably for components with micro-scale dimensions. Other problems are due to the high aspect ratio of the micro structures which makes it necessary to consider the real shape of the component especially for reliability studies. Consequently a wide field has been opened for optical and dimensional metrology with respect to the investigation of microcomponents. Many methods which were tested successfully at big components can be used for microcomponents, too. But new ways must be followed especially in the field of loading, handling and observing micro-scale components. The article deals with optical techniques which have proven to be useful for the investigation of large-scale components and their qualification for the investigation of microcomponents. For the discussion the 3 problem classes mentioned above are taken into account.

Design, manufacturing and test of microcomponents generate new challenges for measurement techniques in general. The non- contacting operation of optical metrology makes it attractive to solve the task of measuring geometric quantities of microparts. So far, speckle interferometry (ESPI) is well established as a measuring tool for analyzing deformation, vibration and strain on a macroscopic level. This paper deals with possibilities and application limits of ESPI in the case of scaling down the object size below one millimeter. In a first part, both spatial resolution and displacement sensitivity of the technique are discussed. Theoretical considerations are shown together with experimental verification. Secondly, a micro speckle interferometer will be presented that has been built for the use with different microscopes. Its capabilities are demonstrated by a practical application. The microcomponent under investigation is a bulk micromachined gyroscope, a demanding object with respect to its multilayer design. Developments aim at increasing the spatial resolution step by step and results obtained with different field of view will demonstrate the progress. Finally, the deformation behavior of an X-shaped torsional spring with a width of 100 micrometer could be characterized.

Two digital speckle-metrology methods are being used for the study of two different phenomena in the field of fluid mechanics. With the out-of-plane digital speckle-pattern interferometry (DSPI), a first step is made in the study of the thermocapillary effect of air-liquid interface curvature changes (Marangoni effect). For the phase distribution evaluation a fast Fourier transform (FFT) based algorithm with additional carrier frequency -- spatial heterodyning (SpH) -- is used. In the experimental stage are registered the optical path changes in the liquid volume, due to the surface shape variations. Experimental results for two liquids (water and glycerin) at different temperatures are shown. The digital speckle-photography (DSPh) is used for the study of sedimentation velocity fields of thin suspensions. A 2D model (Hele-Shaw cell) of 3D flow is used. The developed software is based on the correlation method with unambiguous sign determination. This allows for a complete investigation of the sedimentation front instability. Experimental results are presented, showing velocity fields for different phases of the sedimentation -- emerging and development of 'fingering' and uniform sedimentation.