Die vorliegende Arbeit beschreibt einen neuartigen Ablauf zur Herstellung eines Vibrationssensors auf Waferebene. Die Besonderheit des Sensors liegt in der Reduktion des Spaltmaßes der kapazitiven Elektroden im Anschluss an die Strukturerzeugung. Dies gelingt unter Nutzung des Mikroschweißprozess von Siliziumelementen. Hierbei sieht die innovative Fertigungstechnologie eine Strukturhöhe von 100 μm vor. Zusätzlich wird die Erarbeitung einer Struktur für die Durchführung eines Mikrozugversuchs auf Waferebene beschrieben. Dieser dient der Bestimmung der maximal ertragbaren Zugkraft mikromechanischer Schweißverbindungen und ermöglicht die fertigungsbegleitende Prozesskontrolle. Auf Basis der Messwerte lassen sich Rückschlüsse auf die Geometrie der Schweißstruktur ableiten als auch ein zerstörungsfreies Modell für die Vorhersage der Verbindungsfestigkeit entwickeln. Die Ergebnisbewertung umfasst die qualitative als auch quantitative Charakterisierung der Mikroschweißverbindung sowie die Bewertung des Vibrationssensors in Form eines Funktionsdemonstrators. / The Ph.D. thesis focuses on a novel approach for the fabrication of a MEMS accelerometer on wafer level. The technology relies on the micro welding process of silicon, which is utilized for fixing one component of the capacitive electrode system at a deflected position. Consequently, the gap width of the variable capacitor is reduced below 1 µm for a structure height of 100 µm. The silicon micro welding process is reviewed and investigated. By utilizing a micro tensile test, the maximum bearable load is deduced for different welding geometries. Following these results, a model for predicting the strength of the micro welding site is introduced, allowing for non destructive process monitoring. Finally, the characteristics of the MEMS accelerometer are measured on wafer level and chip level after hermetic packaging respectively.

Silicon and silicon-based materials have been investigated for the fabrication of electronic, optoelectronic, solar, and structural/mechanical devices. To enable the continuous use of silicon-based materials for next generation device applications, new and inexpensive ways of fabricating features of silicon, and silica-based materials are needed. This dissertation investigates: 1) novel techniques for the fabrication of silica and silicon nanofeatures with potential application in the electronics and optoelectronics industry; 2) new designs of photomodifiable material systems (resists) for maskless patterning of silica filled composites for structural/mechanical applications. Sub-micron and nano-scaled features were fabricated onto silicon and silicon oxide substrates using a technique combining block copolymers and laser interference ablation. The sacrificial block copolymers are loaded with metallic salt precursors and patterned with a UV laser to generate device-oriented nanofeatures. New photopolymerizable material systems (negative tone resists) were developed based on curcumin photosensitizer and an epoxy-acrylate, vinylether, and vinylether-acrylate silica¬-loaded material systems. The cationic and radical mechanisms employed by the monomeric systems under a high vapor pressure mercury lamp source were investigated with several materials characterization techniques.

This research explores a novel in-situ technique for monitoring film thickness in the reactive etching process that incorporates a micromachined sensor. The sensor correlates film thickness with changes in resonant frequency that occurs in the micromachined platform during etching. The sensor consists of a platform that is suspended over drive and sense electrodes on the surface of the substrate. As material is etched from the platform, its resonant vibrational frequency shifts by an amount that is proportional to the amount of material etched, allowing etch rate to be inferred. This RIE monitoring methodology exploits the accuracy of resonant micromechanical structures, whereby shifts in the fundamental resonant frequency measure a physical parameter. A majority of these systems require free-standing mechanical movement and utilize a sacrificial layer process as the key technique to develop and release the structure on a substrate. A sacrificial layer technique that incorporates a low temperature sacrificial polymer was utilized to develop and release the suspended RIE sensor with excellent performance and is capable of fabricating other low cost, high performance and reliable suspended MEMS devices. The integration of sensors and electronic circuitry is a dominant trend in the semiconductor industry, and much work and research has been devoted to this effort. The RIE sensor relies on capacitive transduction to detect small capacitance changes and the resulting change in resonant frequency during the RIE process. The RIE sensor's overall performance is limited by the interface circuit, and integration with the proper circuit allows the RIE sensor to function as a highly sensitive measure of etch rate during the RIE process. A capacitive feedback charge amplifier interface circuit, when configured with the RIE senor at the input achieves very low noise sensing of capacitance changes and offers the potential for wide dynamic range and high sensitivity. As an application vehicle, process control was demonstrated in the PlasmaTherm SLR series RIE system located in the Georgia Tech Microelectronics Research Center.

The continuing scaling of integrated circuits beyond 22nm technology node poses increasing challenges to Electromigration (EM) reliability for Cu on-chip interconnects. First, the width of Cu lines in advanced technology nodes is less than the electron mean free path which is 39nm in Cu at room temperature. This is a new size regime where any new scaling effect on EM is of basic interest. And second, the reduced line width necessitates the development of new methods to analyze the EM characteristics. Such studies will require the development of well controlled processes to fabricate suitable test structures for EM study and model verification. This dissertation is to address these critical issues for EM in Cu interconnects. The dissertation first studies the initial void growth under EM, which is critical for measurement of the EM lifetime and statistics. A method based on analyzing the resistance traces obtained from EM tests of multi-link structures has been developed. The results indicated that there are three stages in the resistance traces where the rate of the initial void growth in Stage I is lower than that in Stage III after interconnect failure and they are linearly correlated. An analysis extending the Korhonen model has been formulated to account for the initial void formation. In this analysis, the stress evolution in the line during void growth under EM was analyzed in two regions and an analytic solution was deduced for the void growth rate. A Monte Carlo grain growth simulation based on the Potts model was performed to obtain grain structures for void growth analysis. The results from this analysis agreed reasonably well with the EM experiments. The next part of the dissertation is to study the size effect on the electron wind force for a thin film and for a line with a rectangular cross section. The electron wind force was modeled by considering the momentum transfer during collision between electrons and an atom. The scaling effect on the electron wind force was found to be represented by a size factor depending on the film/line dimensions. In general, the electron wind force is enhanced with increasing dimensional confinement. Finally, a process for fabrication of Si nanotrenches was developed for deposition of Cu nanolines with well-defined profiles. A self-aligned sub-lithographic mask technique was developed using polymer residues formed on Si surfaces during reactive ion etching of Si dioxide in a fluorocarbon plasma. This method was capable to fabricate ultra-narrow Si nanotrenches down to 20nm range with rectangular profiles and smooth sidewalls, which are ideal for studying EM damage mechanisms and model verification for future technology nodes. / text

Eine grundlegende Schwierigkeit in der Röntgenoptik liegt in der Bereitstellung geeigneter Optiken. So ist aufgrund der schwachen Wechselwirkung der Röntgenstrahlung mit Materie der Einsatz brechender Optiken nicht sinnvoll, und es wird auf alternative Konzepte wie Röntgenwellenleiter zurückgegriffen. Röntgenwellenleiter sind nicht-dispersive strahlführende Optiken, welche die Kohärenz der Röntgenstrahlung filtern und als quasi-Punktquellen fungieren. Hierbei wird der Röntgenstrahl in einer oder zwei Dimensionen räumlich beschränkt, wobei der Wellenlängenbereich der Röntgenstrahlung eine Abmessung im sub-100 nm-Bereich erfordert. In der vorliegenden Arbeit wurde ein Verfahren etabliert, mit welchem die Herstellung von Wellenleiterkanälen im sub-50 nm-Bereich in Silizium gelingt. Die Prozessierung basiert hierbei auf einem Schema aus elektronenstrahllithographischer Belichtung, Reaktivem Ionenätzen und Wafer bonding. Das Verfahren ist variabel in Bezug auf verschiedene Wellenleitergeometrien, beispielsweise gekreuzte Wellenleiter und Kanalwellenleiter, ist auf alternative Materialien übertragbar, und erlaubt die Strahlführung auf in einer Dimension gekrümmten Pfaden. Die im Rahmen der vorliegenden Arbeit hergestellten Wellenleiter wurden erfolgreich an verschiedenen Synchrotron-Messplätzen eingesetzt und ihre Fernfelder charakterisiert, und der kohärente Wellenleiterstrahl wurde in der Röntgenmikroskopie und der holographischen Bildgebung eingesetzt. Es finden sich sowohl für die Quellgröße der Wellenleiter als auch für die Auflösung in der Bildgebung Werte im sub-50 nm-Bereich.

ABSTRACT DEVELOPMENT OF A MICRO-FABRICATION PROCESS SIMULATOR FOR MICRO-ELECTRO-MECHANICAL SYSTEMS (MEMS) Yildirim, Alper M.S, Department of Mechanical Engineering Supervisor: Asst. Prof. Dr. Melik D&ouml / len December 2005, 140 pages The aim of this study is to devise a computer simulation tool, which will speed-up the design of Micro-Electro-Mechanical Systems by providing the results of the micro-fabrication processes in advance. Anisotropic etching along with isotropic etching of silicon wafers are to be simulated in this environment. Similarly, additive processes like doping and material deposition could be simulated by means of a Cellular Automata based algorithm along with the use of OpenGL library functions. Equipped with an integrated mask design editor, complex mask patterns can be created by the software and the results are displayed by the Cellular Automata cells based on their spatial location and plane. The resultant etched shapes are in agreement with the experimental results both qualitatively and quantitatively. Keywords: Wet Etching, Anisotropic Etching, Doping, Cellular Automata, Micro-fabrication simulation, Material Deposition, Isotropic Etching, Dry Etching, Deep Reactive Ion Etching

Measurement of absorption spectra of plasma during reactive ion etching enables characterization of etched species and control over the etching process. Aim of this diploma thesis is to design spectroscope with Czerny-Turner configuration for reactive ion etching system. Developed spectroscope achieves 1 nm resolution in 350-800 nm range. Device was tested during reactive ion etching of silicon.

The work is focused on research and development of a suitable method for creating a selective emitter for the visible and near infrared region so that they are able to work optimally together with silicon photovoltaic cells in a thermophotovoltaic system. The aim of the work was to develop a new method of creating very fine structures outside the current standard, which will increase the emissivity of the base material to meet the needs of a selective emitter for the VID and NIR region. The methods available to us for the creation of structures were chosen, from which we eliminated all unsuitable ones and we introduced the optimal procedure and parameters for their creation for the selected method. In this work, we focused on both ceramic and metallic materials, whose heat resistance and selective properties are key to this work. Part of the development of the emitter structures was also the need for pretreatment of the substrate itself, where great emphasis was placed on the purity of materials and surface roughness. Since ceramic materials cannot achieve a surface roughness so low that the desired structures can be formed, these materials have been purposefully used primarily for the purpose of combining the base material with thin layers of other high temperature material. Their compatibility and suitability were verified in terms of adhesion and subsequent heat resistance. The main material for the formation of fine structures was purposefully chosen tungsten, for which we verified the influence of the formed structure on the emissivity as well as the thermal stability during long-term exposure to high temperatures. The work thus represents not only a new method of creating very fine structures, which are not normally formed in such subtlety, but also opens the way to new possibilities of combining more materials to achieve the required selectivity of the thermophotovoltaic emitter.

The aim of this work is to design fully working measuring system for the reactive ion etching system (RIE). The Michelson interfometer, previously developed in Ústav přístrojové techniky, v.v.i., is used in this work. The theoretical part is aimed at description of interferometric methods for precise measuring of length. In next part the etching proces with RIE is described. In practical part the testing system was constructed from the parts of Thorlabs company . The functionality was controlled with this system and the results of measuring were compared with the profilometer. In next step technical drawings were created and the whole system was made.

Un microgyromètre 3 axes permet avec une structure unique de mesurer la vitesse de rotation d’un objet autour des trois axes de l’espace. Les micro-gyromètres 3 axes existants sont peu nombreux et typiquement résonants, fabriqués en technologie silicium par micro-usinage de surface, à transductions électro-statiques, et conçus pour des applications de fort volume ou la taille et le coût sont des critères majeurs. Dans cette thèse nous avons étudié la transduction et le procédé de fabrication d’un gyromètre résonant 3 axes à actionnement et détection piézoélectriques, fabriqué par micro-usinage de volume dans du GaAs semi-isolant, et dont les performances sont potentiellement très supérieures à l’état de l’art tout en conservant une taille et un coût limité. Ce microgyromètre nécessite une transduction piézoélectrique 3D et un routage des connexions électriques qui ont été modélisés et optimisés pour réduire les couplages parasites entre les modes de détection et le mode pilote. Un procédé original de fabrication collective du microgyromètre a été développé, modélisé et caractérisé. Ce procédé utilise notamment une gravure ionique réactive très profonde et traversante du GaAs dans un plasma BCl3-Cl2. Il est démontré pour la première fois qu’une gravure anisotrope traversante de tranchées de 450 μm de profondeur peut être réalisée grâce à une optimisation des paramètres de gravure et à l’utilisation d’un masque en résine. Un procédé original de dépôt et de délimitation d’électrodes Au/Cr sur les flancs verticaux d’une structure gravée par évaporation sous incidence oblique avec rotation du substrat et à travers un masque pochoir en film sec photosensible a aussi été étudié en détail. Une caractérisation fine de la structure cristalline, de la résistivité et des contraintes mécaniques avant, pendant et après recuit des couches Au/Cr poreuses évaporées sous incidence oblique a été menée. Des micro-gyromètres complets avec tout le système de transduction 3D ont été réalisés. Des premières caractérisations par vibrométrie optique hors du plan et dans le plan des gyromètres réalisés démontrent des résultats encourageants. Enfin, différentes voies d’amélioration de la conception et du procédé sont proposées. / A 3 axis gyroscope allows, with a single mechanical structure, the measurement of rotation rates of an object around 3 perpendicular spatial axes. Existing 3 axis microgyroscopes are scarce and typically resonating, made in silicon technology by surface micromachining, use electrostatic transductions and are designed for high volume applications where size and cost are major characteristics. In this thesis we investigated the transduction and fabrication process of a resonating 3 axis microgyroscope having piezoelectric actuation and detection, made in semi-insulating GaAs by bulk micromachining, and with performances potentially much higher than state of the art while limiting the size and cost. This microgyroscope requires a 3D piezoelectric transduction and circuitry which were modelled and optimized to reduce cross-talks effects. An original batch fabrication process was developed, modelled and characterized. This process notably makes use of very deep through wafer reactive ion etching of GaAs in a BCl3-Cl2 plasma. It is demonstrated for the first time that a through wafer highly anisotropic etching of 450 μm deep trenches can be realized owing to etching parameters optimization and the use of a resist masking layer. An original deposition and patterning process of Au/Cr electrodes on the vertical walls of an etched structure by oblique evaporation on rotated substrate through a dry film shadow mask has also been investigated in details. A fine characterization of the crystallographic structure, resistivity and mechanical stress before, during and after annealing of Au/Cr films evaporated under oblique incidence has been performed. Full microgyroscopes with the whole 3D tranduction system were realized. Preliminary characterizations of realized gyroscopes by out-of-plane and in-plane optical vibrometry demonstrated promising results. Finally, different ways to improve the design and fabrication process are proposed.