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El objetivo de este estudio fue evaluar el efecto sobre la fuerza adhesiva (SBS), adhesivo remanente, y superficie del esmalte del recementado de brackets nuevos en la misma superficie de esmalte utilizando distintos métodos de acondicionamiento del esmalte.Utilizamos 135 incisivos bóvinos. Los brackets fueron cementados al esmalte con: (1)acido-fosfórico al 37%, (2)ácido-fosfórico al 37% (antes del primer cementado pero no en los siguientes cementados), (3)Transbond-Plus-Self-Etching-Primer® (TSEP) y (4)acondicionador que no precisa lavado (NRC). Los brackets fueron cementados y descementados tres veces utilizando el mismo procedimiento de acondicionamiento con la excepción del grupo 2 donde no se volvió a grabar con ácido-fosfórico al 37% en la segunda ni tercera secuencias de cementado. SBS y el adhesivo remanente fueron evaluados para cada descementado. Se realizaron observaciones al MEB para cada secuencia de acondicionamiento. Se realizó el análisis estadístico utilizando ANOVA, test de Mann-Whitney, y test de Kruskal-Wallis. / The aims of this study were to evaluate the effect on shear bond strength (SBS), adhesive remnant, and enamel surface of repeated bonding of new brackets on the same tooth using different methods of enamel conditioning.135 bovine incisors were used. Brackets were bonded to enamel using oneof the following conditioning procedures: (1) 37% phosphoric-acid, (2) 37% phosphoric-acid (prior to first bond but not for further bonds), (3) Transbond Plus Self Etching Primer® (TSEP), and (4) non-rinse-conditioner (NRC). Brackets were sequentially bonded and debonded three timesfollowing the same conditioning procedure with the exception of group 2 where 37% phosphoric-acid was not reapplied prior to the second and third bonding sequences. SBS and adhesive remnant were evaluated for each debond. SEM observations were made for each conditioning sequence. Statistical analysis was undertaken using ANOVA, Mann-Whitney, and Kruskal-Wallis tests.

This thesis presents the optimization of deep reactive ion etching process (DRIE) to achieve high precision 3-dimensional integrated micro electro mechanical systems (MEMS) sensors with high aspect ratio structures. Two optimization processes have been performed to achieve 20 &amp / #956 / m depth for 1 &amp / #956 / m opening for a dissolved wafer process (DWP) and to achieve 100 &amp / #956 / m depth for 1 &amp / #956 / m opening for silicon-on-glass (SOG) process. A number of parameters affecting the etch rate and profile angle are investigated, including the step times, etch step pressure, platen power, and electrode temperature. Silicon etch samples are prepared and processed in METU-MET facilities to understand and optimize the DRIE process parameters that can be used for the production of MEMS gyroscopes and accelerometers. The etch samples for DWP are masked using a photoresist, Shipley S1813. After the optimization process, vertical trench profiles are achieved with minimum critical dimension loss for trench depths up to 20 &amp / #956 / m. Since the selectivity of the resist is not sufficient for 100 &amp / #956 / m deep trench etch process, silicon dioxide (SiO2) is used as the mask for this process. At the end of the optimization processes, more than 100 &amp / #956 / m depth for 1 &amp / #956 / m opening with almost vertical sidewalls are achieved. In summary, this study provides an extensive understanding of the DRIE process for successful implementations of integrated MEMS sensors.

The considerable interest in nanomaterials and nanotechnology over the last decade is attributed to Industry's desire for lower cost, more sophisticated devices and the opportunity that nanotechnology presents for scientists to explore the fundamental properties of nature at near atomic levels. In pursuit of these goals, researchers around the world have worked to both perfect existing technologies and also develop new nano-fabrication methods; however, no technique exists that is capable of producing complex, 2D and 3D nano-sized features of arbitrary shape, with smooth walls, and at low cost. This in part is due to two important limitations of current nanofabrication methods. First, 3D geometry is difficult if not impossible to fabricate, often requiring multiple lithography steps that are both expensive and do not scale well to industrial level fabrication requirements. Second, as feature sizes shrink into the nano-domain, it becomes increasingly difficult to accurately maintain those features over large depths and heights. The ability to produce these structures affordably and with high precision is critically important to a number of existing and emerging technologies such as metamaterials, nano-fluidics, nano-imprint lithography, and more. Summary To overcome these limitations, this study developed a novel and efficient method to etch complex 2D and 3D geometry in silicon with controllable sub-micron to nano-sized features with aspect ratios in excess of 500:1. This study utilized Metal-assisted Chemical Etching (MaCE) of silicon in conjunction with shape-controlled catalysts to fabricate structures such as 3D cycloids, spirals, sloping channels, and out-of-plane rotational structures. This study focused on taking MaCE from a method to fabricate small pores and silicon nanowires using metal catalyst nanoparticles and discontinuous thin films, to a powerful etching technology that utilizes shaped catalysts to fabricate complex, 3D geometry using a single lithography/etch cycle. The effect of catalyst geometry, etchant composition, and external pinning structures was examined to establish how etching path can be controlled through catalyst shape. The ability to control the rotation angle for out-of-plane rotational structures was established to show a linear dependence on catalyst arm length and an inverse relationship with arm width. A plastic deformation model of these structures established a minimum pressure gradient across the catalyst of 0.4 - 0.6 MPa. To establish the cause of catalyst motion in MaCE, the pressure gradient data was combined with force-displacement curves and results from specialized EBL patterns to show that DVLO encompassed forces are the most likely cause of catalyst motion. Lastly, MaCE fabricated templates were combined with electroless deposition of Pd to demonstrate the bottom-up filling of MaCE with sub-20 nm feature resolution. These structures were also used to establish the relationship between rotation angle of spiraling star-shaped catalysts and their center core diameter. Summary In summary, a new method to fabricate 3D nanostructures by top-down etching and bottom-up filling was established along with control over etching path, rotation angle, and etch depth. Out-of-plane rotational catalysts were designed and a new model for catalyst motion proposed. This research is expected to further the advancement of MaCE as platform for 3D nanofabrication with potential applications in thru-silicon-vias, photonics, nano-imprint lithography, and more.

Du fait de la réduction des dimensions en microélectronique, les procédés de gravure par plasmas ne peuvent plus satisfaire aux exigences de l'industrie. De nouvelles stratégies sont en cours de développement. Ce travail consiste en l'étude de plasmas pulsés de HBr/O2 comme une alternative pour la gravure du silicium. Divers diagnostics dans un réacteur industriel 300 mm sont utilisés pour caractériser le plasma tandis que la gravure du silicium est étudiée par XPS et par microscopie électronique. Lorsque le plasma est pulsé à faible rapport cyclique, sa température et sa dissociation sont fortement réduits. Le flux de Br radicalaire par rapport à la période ON du plasma augmente tandis que l'influence du radical O diminue, ce qui conduit à une amélioration de la sélectivité par rapport au SiO2 et à une gravure plus homogène. Les profils des structures gravées peuvent être contrôlés par la formation de la couche de passivation sur les flancs dépendant également du rapport cyclique. / The continuous downscaling in microelectronics imposes increasing demands on the plasma processes and traditional ways for process optimization reach their limits. New strategies are needed and innovations in the field of plasma processes are being developed: e.g. the use of pulsed plasmas. In this thesis, a pulsed HBr/O2 etch plasma is studied. Various in-situ diagnostics are used to characterize pulsed plasmas in an industrial 12” etch reactor. The silicon etching is investigated by XPS and electron microscopy. We show that the plasma dissociation and temperature are reduced if the plasma is pulsed at low duty cycles. The Br radical flux with respect to the on-time of the plasma is increased and the influence of the O radical is decreased, leading to enhanced time compensated silicon etch rates, a higher selectivity towards SiO2 and a more homogeneous etching. The pattern profiles can be controlled via the sidewall passivation layer formation that is closely linked to the duty cycle.

The problem with which this comparative investigation is concerned is the application of a photographically derived image to glass. The image used originated from an ordinary thirty-five-millimeter color slide. This slide, through photographic darkroom manipulation, was translated into thirty individually different, black and white films of four-by-five-inch size. Selected films were then enlarged onto eleven-by-fourteen-inch, Kodalith film. These enlarged films were contact exposed to Ulano's Blue Poly-3, a presensitized silkscreen photofilm. This in turn was adhered to twelve double X silk which was tautly stretched in a wooden frame.