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.

<p>Dry etching is an important technique for pattern transferin fabrication of most opto-electronic devices, since it canprovide good control of both structure size and shape even on asub-micron scale. Unfortunately, this process step may causedamage to the material which is detrimental to deviceperformance. It is therefore an objective of this thesis todevelop and investigate low damage etching processes for InPbased devices.</p><p>An ion beam system in combination with hydrocarbon (CH₄) based chemistries is used for etching. At variousion energies and gas flows the etching is performed in twomodes, reactive ion beam etching (RIBE) and chemical assistedion beam etching (CAIBE). How these conditions affect both etchcharacteristics (e.g. etch rates and profiles, surfacemorphology and polymer formation) and etch induced damage (onoptical and electrical properties) is evaluated and discussed.Attention is also paid to the effects of typical post etchingtreatments such as annealing on the optical and electricalproperties. An important finding is the correlation betweenas-etched surface morphology and recovery/degradation inphotoluminescence upon annealing in PH₃. Since this type of atmosphere is typical forcrystal regrowth (an important process step in III/Vprocessing) a positive result is imperative. A low ion energy N₂/CH₄/H₂CAIBE process is developed which not onlysatisfies this criteria but also exhibits good etchcharacteristics. This process is used successfully in thefabrication of laser gratings. In addition to this, the abilityof the ion beam system to modify the surface morphology in acontrollable manner is exploited. By exposing such modifiedsurfaces to AsH₃/PH₃, a new way to vary size and density of InAs(P)islands formed on the InP surfaces by the As/P exchangereaction is presented.</p><p>This thesis also proposes a new etch chemistry, namelytrimethylamine ((CH₃)₃N or TMA), which is a more efficient methyl sourcecompared to CH₄because of the low energy required to break the H₃C-N bond. Since methyl radicals are needed for theetching it is presumably a better etching chemistry. A similarinvestigation as for the CH₄chemistry is performed, and it is found that bothin terms of etch characteristics and etch induced damage thisnew chemistry is superior. Extremely smooth morphologies, lowetch induced damage and an almost complete recovery uponannealing can be obtained with this process. Significantly,this is also so at relatively high ion energies which allowshigher etch rates.</p><p><b>Keywords:</b>InP, dry etching, ion beam etching, RIBE,CAIBE, hydrocarbon chemistry, trimethylamine, As/P exchangereaction, morpholoy, low damage, AFM, SCM, annealing</p>

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

L'industrie de la microélectronique s'appuie sur l'évolution constante de la miniaturisation des transistors. D'ici 2016, cette industrie atteindra le nœud technologique 16 nm dans lequel il faudra être capable de graver des structures de dimensions nanométrique ayant de très forts facteurs d'aspect. Cependant, les procédés de gravure actuels montrent de sérieuses limitations en termes de contrôle des profils et des dimensions critiques lorsqu'il faut graver de telles structures. Les problèmes rencontrés sont liés d'une part à des limitations intrinsèques des procédés plasmas et d'autre part à l'apparition de nouveaux phénomènes lorsque la dimension des structures à graver devient nanométrique. Dans le cadre de cette thèse, un nouveau mode de fonctionnement des sources à plasma est étudié pour développer des procédés de gravure adaptés aux prochaines générations de circuits intégrés : les plasmas modulés en impulsions courtes. Les premiers travaux réalisés s'appuient sur de puissantes techniques d'analyses du plasma (spectroscopie d'absorption VUV, sonde de flux ionique, analyseur électrostatique) dans le but de mettre en évidence l'impact des paramètres de la modulation en impulsion du plasma sur ses caractéristiques physicochimiques (flux et énergie des radicaux et des ions). Ces diagnostics ont tout d'abord permis de définir très clairement les conséquences de la modulation en impulsion du plasma sur les flux de radicaux réactifs qui bombardent le substrat : le rapport de cycle est LE paramètre clé pour contrôler la chimie du plasma car il permet de contrôler le taux de fragmentation du gaz par impact électronique. Dans un second temps, nous avons également démontré que dans les plasmas électronégatifs et pour une puissance RF de polarisation donnée, l'énergie des ions augmente lorsque le rapport de cycle diminue. Fort de ces connaissances fondamentales sur les plasmas, des analyses des surfaces (XPS, MEB, Raman…) ont permis de comprendre les mécanismes mis en jeux lors de l'interaction plasma- surface. Ainsi, il a été possible de développer des procédés de gravure pulsés pour plusieurs étapes de la grille de transistor (prétraitement HBr, gravure du Si-ARC, gravure du pSi). Les prétraitements HBr sont incontournables pour réduire la rugosité de bord de ligne de transistor. Lors de cette étape, une couche riche en carbone limite l'effet bénéfique des UV du plasma sur la diminution de la rugosité. Grâce à l'utilisation des plasmas pulsés, l'origine de cette couche a été mise en évidence : elle résulte du dépôt sur les motifs d'espèces carbonées non volatiles issues de la photolyse de la résine qui sont relâchées dans le plasma. Dans ce système bicouche, les contraintes de la couche carbonée dure vont se relaxer dans le volume mou de la résine par phénomène de « buckling » qui se traduit par une hausse de la rugosité de bord de ligne. Nous avons montré que cela peut être évité en minimisant l'épaisseur de cette couche, ce qui peut être obtenu notamment en pulsant le plasma. La gravure de la couche anti-réflective Si-ARC qui sert de masque dur et celle de la grille en poly Silicium reposent sur l'utilisation de plasmas fluorocarbonés. Mais dans ce type de plasma, la production de précurseurs pour la polymérisation est diminuée quand le plasma est pulsé, conduisant à une perte de sélectivité et d'anisotropie. Les plasmas synchronisés pulsés ne sont donc pas de bons candidats pour les étapes de gravure considérées. Pour pallier à ce problème, un autre mode de polarisation a été étudié : les plasmas pour lesquels seule la puissance de polarisation est pulsée. Dans le cas de la gravure du Si-ARC, il est possible d'obtenir des profils très anisotropes avec une sélectivité vis-à-vis de la résine nettement améliorée. Pour la gravure du Silicium, les effets d'ARDE ont pu être diminués tout en améliorant la sélectivité. Ces résultats sont très encourageants. / Microelectronics industry is based on the continuous transistor downscaling. By the year 2016, the 16nm technological node would be achieved, so that structures with nanometric dimensions and high aspect ratio would have to be etch. However, traditional etching processes shows major limitations in terms of pattern profiles control and critical dimensions when such structures have to be etch. The encountered problems are related directly to intrinsic limitations of plasmas processes but also to the emergence of new phenomena’s when the dimensions of structures to etch become nanometric. In the framework of this thesis, a new strategy to produce plasma has been evaluated to develop etching plasmas processes adapted to next integration circuit generations: the pulsed plasmas. Over a first phase, the impact of plasma pulsing parameters (frequency and duty cycle) on the plasma physico-chemical characteristics has been highlight. This has been achievable thanks to advanced plasma analyse techniques (VUV broad band absorption spectroscopy, ion flux probe, retarding electrical field analyser…) developed to allow time resolved measurements. For the neutral flux, diagnostics have revealed that duty cycle is THE key control knob to tune the plasma. Indeed, a low duty cycle leads to reduced parent gas fragmentation and thus a reduced chemical reactivity. On the other hand, in electronegative plasmas and for constant RF power, we have demonstrated that ion energy is considerably increased when the ions flux is decreased (i.e. when the duty cycle is decreased). Then, surface analyses (XPS, SEM, Raman spectroscopy…) brought out the mechanisms involved during the plasma-surface interaction. Deeper comprehension of impact of pulsing parameters enables to develop pulsed plasmas processes more easily. These works are focused on the top of the transistor gate and deal with the following steps: HBr cure, Si-ARC etching, poly-silicon etching. HBr cure is an essential pre-treatment of the 193 nm photoresist to decrease the Line Width Roughness (LWR) of transistor gate. During this step, a carbon rich layer is formed on the surface of the resist pattern and degrades the beneficial action of UV plasma light on LWR reduction. Thanks to use of pulsed plasmas, the origin of this carbon rich layer has been highlight: UV induced modifications in polymer bulk lead to outgassing of volatiles carbon-based products in the plasma. These carbon containing moieties are fragmented by electron impact dissociation reaction in the plasma, which create sticking carbon based precursors available for re-deposition on the resist patterns. The impact of this layer on the LWR and resist pattern reflow is studied, and a possible mechanical origin (i.e. buckling instabilities) is highlighted. Finally, we showed that the use of pulsed HBr curing plasma allows to reduce and control the thickness of the graphite-like layer and to obtain LWR reduction that are comparable to VUV treatment only. The Si-ARC layer, used as hard mask, and the poly-silicon gate etching are based on the use of fluorocarbon plasmas. However, in these plasmas, the production of radicals enable for the polymerisation is decreased when the duty cycle is reduced. It leads to loss of both anisotropy and selectivity. Synchronised pulsed plasmas are then not adapted to such etching processes. To overcome this problem, a new way to produce plasma has been studied: the ICP source power is maintained constant and only the bias power is pulsed. Regarding Si-ARC etching, very anisotropic profiles are obtained and the Si-ARC to resist selectivity is enhanced while pulsing the rf bias to the wafer. In the case of poly-silicon etching, the ARDE effects are significantly reduced while the selectivity regarding the oxide is improved. These results are very promising for the development of polymerising plasmas processes.

Ce travail porte sur le développement d’une technique de structuration de surface pour le silicium. Celle-ci repose sur trois étapes essentielles : la lithographie, l’implantation ionique et le retrait par voie humide. Le motif formé par lithographie est transféré par homothétie dans la couche sous-jacente de silicium grâce à l’implantation ionique. Après le retrait du masque de résine, le substrat est traité par voie humide en vue de retirer des zones localement implantées. Le motif initial défini par la lithographie est ainsi révélé dans le silicium.La compréhension des modifications induites par l’implantation ionique dans le substrat nous a permis de réaliser avec succès un transfert dans le silicium. Nous avons principalement étudié les défauts générés par deux types d’ions : l’argon et l’hydrogène, à travers un certain nombre de techniques de caractérisation. Sur la base de cette étude, les différents traitements humides du silicium ont été investigués : gravure alcaline, gravure acide, dissolution par anodisation. L’optimisation des conditions d’implantation et des paramètres de retrait humide a permis l’obtention de structures 2D puis 3D.La faisabilité de cette technique de structuration a également été démontrée sur d’autres matériaux comme le SiOCH et le nitrure de silicium. / This thesis deals with the development of a patterning process for silicon substrates. Based on ion implantation through a resist pattern to locally modified the underneath layer. Wet etching processes have been developed to reveal the shapes transferred into the silicon substrate. Thanks to morphological, physical and chemical characterizations, modifications induced by ion implantation have been identified and understood.Two ion species (argon and hydrogen) were used in this thesis in order to assess either physical or chemical modifications in silicon substrate. Several wet chemistries: alkaline, acid and dissolution by anodization, were investigated to reveal the final shape. The optimization of the implantation and wet etching processes allowed to obtain 2D and 3D structures with silicon substrate.Moreover, our approach has been successfully implemented to pattern 2D shapes in SiOCH and silicon nitride.

Malgré les innovations technologiques, les éoliennes restent sujettes à des défaillances prématurées de composants mécaniques imposants, ayant des conséquences considérables sur le coût de l’énergie. Parmi les défaillances majeures au sein des roulements d’éoliennes, un mode de fatigue de contact atypique se caractérise par de vastes réseaux de fissures ramifiées avec des phases microstructurales adjacentes d’apparence blanche à l’origine de la dénomination White Etching Cracks (WEC). Contrairement à la fatigue de contact classique, les WEC apparaissent pour un nombre de cycles et des charges relativement faibles, menant à une défaillance du composant imprévisible selon les modèles de durée de vie actuels. Les WEC ont été observés chez tous les roulementiers, dans diverses applications industrielles et pour différents types de roulements, éléments, lubrifiants, aciers et traitements thermiques. Ce manque de dénominateur commun rend les WEC difficilement reproductibles sur bancs d’essai sans chargement artificiel en hydrogène de l’acier. Ainsi, pour le moment, la formation des WEC ne fait pas l’objet d’un consensus. Une analyse des reproductions de WEC a été menée afin d’en comprendre les mécanismes tribologiques. Des protocoles expérimentaux ont été établis pour révéler les WEC, souvent situés à des positions inhabituelles par rapport au contact. Leur reproduction sur des roulements standards, chargés ou non en hydrogène, a permis de démontrer que le chargement artificiel en hydrogène, jusque-là couramment employé pour étudier la défaillance, reproduit des faciès identiques mais semble modifier l’initiation des WEC. Ainsi, des reproductions de WEC sans chargement en hydrogène et dans des configurations différentes ont été comparées afin d’appréhender les phénomènes tribologiques à l’origine des WEC. Les résultats suggèrent que l’initiation est principalement déclenchée par des phénomènes de surfaces avec l’absorption tribochimique d’hydrogène au niveau des surfaces métalliques fraîches sur la piste de roulement ou au niveau des flancs de microfissures superficielles. La propagation est ensuite assistée chimiquement par l’hydrogène concentré en pointe de fissure. Un arbre des causes étendu révèle que les WEC peuvent être associées à de multiples combinaisons de conditions opératoires qui semblent cependant conduire à des paramètres tribologiques similaires à l’échelle du contact avec, notamment, des cinématiques de glissement, des formulations de lubrifiants spécifiques et des paramètres tribochimiques catalyseurs comme la présence d’eau et/ou d’électricité. Une vaste campagne d’essai a alors été conduite sur un tribomètre bi-disques afin de simuler la fatigue de contact. Les résultats confirment que les facteurs influents identifiés ne sont pas pour autant auto-suffisants. La formation des WEC repose sur un équilibre instable entre aspects matériaux, mécaniques et tribochimiques, à maîtriser pour concevoir des solutions industrielles. / Despite constant expansion and engineering progress, wind turbines still present unexpected failures of heavy duty mechanical components drastically affecting the cost of energy. Among the most prevalent tribological failures in wind turbine rolling element bearings, a peculiar rolling contact fatigue mode has been associated to broad subsurface three-dimensional branching crack networks bordered by white etching microstructure, and thus named White Etching Cracks (WEC). Compared to conventional microstructural alterations, WECs tend to develop at moderate loads and cycles eventually leading to premature failures that remain unpredictable using fatigue life estimations. Far from being generic to specific manufacturers, WECs occur in various industrial applications, for various bearing types, components, lubricants, steels grades and heat treatments. As WEC occurrences present no common evident denominator, they remain delicate to reproduce on laboratory test rigs without prior artificial hydrogen charging, so that no consensus on WEC formation mechanisms have been confirmed yet. In this study, a thorough tribological analysis of WEC formation mechanisms has been led. Expertise protocols have been established to best reveal and observe WECs that commonly develop at unconventional locations versus the contact area. First analysis of WEC reproductions on standard rolling element bearings either hydrogen precharged or kept neutral have signified that artificial hydrogen charging, commonly employed to apprehend the failure mode, results in similar WEC morphologies but tends to alter WEC tribological initiation. In consequence, WEC reproductions in remarkably different configurations but without hydrogen charging have been compared in order to propose a better understanding of WEC surface-affected formation mechanisms: first, initiation via tribochemical hydrogen permeation at nascent steel surfaces formed either directly at the raceway or at surface microcracks flanks and second, propagation by local hydrogen embrittlement at crack tips function of the stress state. An extensive root cause analysis have then been led suggesting that WEC may be associated to various combinations of macroscopic operating conditions that often interact and come down to similar tribological parameters including high sliding energy thresholds, specific lubricant formulations and tribochemical drivers such as water contamination and/or electrical potentials. Further investigations on a minimalist twin-disc fatigue tribometer have provided additional evidence that WEC influent drivers are non-self-sufficient, supporting that WEC formation mechanisms rely on a subtle equilibrium between tribo-material, tribo-mechanical and tribo-chemical drivers that all should be mastered to design efficient and durable countermeasures.

<p>Gleđ je supstrat adhezije direktnih i indirektnih ispuna, ljuspi, splintova, zalivača i ortodontskih bravica. Adhezija između materijala i zubnog tkiva je ključna za uspe&scaron;no sprovođenje različitih stomatolo&scaron;kih intervencija. Ova veza, bez obzira na brojnost i raznovrsnost novih materijala nije u potpunosti re&scaron;ena. CILJ: Ispitati mehaničke i hemijske osobine gleđi nakon tretmana različitim kondicionerima za pripremu gleđi. Odrediti tvrdoću i modul elastičnosti, odrediti hemijski udeo minerala kalcijuma i fosfata u povr&scaron;inskom sloju gleđi pre i posle nagrizanja različitim kiselinama i utvrditi uticaj prizmatičnosti gleđi na stepen nagrizanja gleđi primenom različitih kiselina. METODE: Sprovedeno je in vitro istraživanje na ekstrahovanim humanim zubima. U odnosu na primenjeni kondicioner analizirano je 192, od toga 96 uzoraka stalnih zuba i 96 uzoraka mlečnih zuba. Pripremljeni uzorci gleđi su analizirani pre i nakon primene četiri vrste kondicionera: 37% ortofosforne kiseline (Kerr, Gel etchant), 10% poliakrilne kiseline (GC, Dentin Conditioner), monomera estra fosforne kiseline (GC G bond), hidroksietilmetakrilata sa fosfornom kiselinom (3M Unitek, Transbond&trade; Plus Self Etching Primer). Određivana je tvrdoća i modul elastičnosti gleđi nanoindentacijom, struktura povr&scaron;inskog sloja gleđi pomoću skening elektronske mikroskopije, dok je hemijski sastav povr&scaron;inskog sloja gleđi određen metodom energetske disperzione spektroskopije. Rezultati modula elastičnosti unutar grupe mlečnih zuba ukazali su na postojanje statistički značajnih razlika između rezultata netretirane okluzalne povr&scaron;ine i svih tretiranih uzoraka okluzalne povr&scaron;ine, dok analiza tvrdoće gleđi u istoj grupi, ukazala je na statistički značajne razlike između vrednosti netretiranih i svih tretiranih uzoraka, na svim povr&scaron;inama, osim na uzorcima bukalne povr&scaron;ine tretiranih poliakrilnom kiselinom. U grupi stalnih zuba, postoje statistički značajne razlike vrednosti modula elastičnosti između uzoraka tretiranih ortofosfornom kiselinom, bez obzira na povr&scaron;inu zuba, u odnosu na grupe u kojima su kori&scaron;ćeni drugi kondicioneri, osim kada su poređeni uzorci lingvalne povr&scaron;ine stalnih zuba tretirani ortofosfornom kiselinom sa uzorkom - iste povr&scaron;ine tretirane Transbondom. Rezultati tvrdoće gleđi stalnih zuba pokazali su statistički značajne razlike između netretirane, kontrolne grupe i svih grupa testiranih kondicionera, bez obzira na ispitivanu povr&scaron;inu zuba. Svaki primenjeni kondicioner promenio je povr&scaron;insku morfologiju uzorka. Ortofosforna i poliakrilna kiselina, u najvećoj meri su uticala na pojavu polja nagrizanja tipa 1 i tipa 2. Primenom G bonda i Transbonda pored tipa 1, veliki udeo polja nagrizanja bio je tipa 5. Analiza hemijskih elemenata povr&scaron;inskog sloja gleđi uzoraka pre i nakon kondicioniranja ukazala je na smanjenje udela analiziranih elemenata, osim kiseonika čiji se maseni udeo povećao nakon tretmana sa svim kondicionerima u grupi stalnih i mlečnih zuba. ZAKLJUČAK: Vrednosti tvrdoće gleđi i vrednosti modula elastičnosti značajno se smanjuju nakon nagrizanja gleđi u stepenu koji je u zavisnosti od primenjenog kondicionera. Efekat nagrizanja aprizmatične gleđi je značajno manji u odnosu na stepen nagrizanja prizmatične gleđi, primenom svih testiranih kondicionera. Hemijski udeo minerala kalcijuma i fosfata u povr&scaron;inskom sloju gleđi je značajno niži posle nagrizanja u odnosu na vrednosti pre nagrizanja gleđi, međutim sam odnos Ca i P se ne menja.</p> / <p>Dental enamel is a substrate for the adhesion of direct and indirect fillings, venners, splints, fissure sealants and orthodontic brackets. Adhesion between the material and dental tissue is key to success of various interventions in dentistry. Despite the abundance and variety of new materials, adhesion has not been fully resolved. OBJECTIVES: To investigate the mechanical and chemical properties of the enamel after treatment with different conditioners. Determine the hardness and modulus of elasticity, the chemical content of calcium and phosphate minerals in the surface layer of the enamel before and after etching with different acids, and define the effect of enamel prismaticity on the degree of demineralisation by applying different acids. METHODS: An in vitro study was performed on extracted human teeth. In relation to the conditioner used, 192 were analyzed, of which 96 were permanent teeth and 96 were decidous teeth. Prepared enamel samples were analyzed before and after the application of four types of conditioner: 37% orthophosphoric acid (Kerr, Gel etchant), 10% polyacrylic acid (GC, Dentin Conditioner), phosphoric acid ester monomer (GC G bond), hydroxyethyl methacrylate with phosphoric acid ( 3M Unitek, Transbond &trade; Plus Self Etching Primer ). The hardness and modulus of elasticity of the enamel were determined by nanoindentation, the structure of the enamel surface layer by scanning electron microscopy, while the chemical composition of the enamel surface layer was determined by energy dispersive spectroscopy. RESULTS: The results of the modulus of elasticity within the group of decidous teeth indicated statistically significant differences between the results of untreated occlusal surface and all treated occlusal surface samples, while the analysis of the hardness of the enamel in the same group indicated statistically significant differences between the values of untreated and all treated samples, on all surfaces except buccal surface samples treated with polyacrylic acid. In the group of permanent teeth, there are statistically significant differences in the value of the modulus of elasticity between the samples treated with orthophosphoric acid, regardless of the tooth surface, compared to the groups in which other conditioners were used, except when the samples of the lingual surface of permanent teeth were treated with orthophosphoric acid in comparison to same sample group treated with Transbond. The results of the hardness of the permanent tooth enamel showed statistically significant differences between the untreated, control group and all groups of conditioners used, regardless of the tooth surface tested. Each conditioner applied changed the surface morphology of the sample. Orthophosphoric and polyacrylic acid, to a large extent, influenced the appearance of etching patterns type 1 and type 2. Using G bond and Transbond alongside to type 1, a large proportion of the etching pattern was type 5. Analysis of the chemical components of the surface layer of the enamel samples before and after conditioning indicated reduction of the proportion of analyzed elements, except for oxygen whose mass fraction increased after treatment with all conditioners in the permanent and deciduous teeth group. CONCLUSION: The values of the hardness of the enamel and the values of the modulus of elasticity decrease significantly after etching of the enamel to a degree that depends on the conditioner applied. The etching effect on aprismatic enamel is significantly smaller than the degree of demineralisation of the prismatic enamel in all conditioners tested. The chemical content of calcium and phosphate minerals in the surface layer of the enamel is significantly lower after the conditioning, however the Ca and P ratio does not change.</p>

The fabrication of zone plate lenses that are used for focusing X-rays relies on nanofabrication techniques such as e-beam lithography, reactive ion etching, and electroplating. The circular grating-like zone plate pattern can have a smallest half-period, a so-called zone width, of down to 20 nm while it also needs to have a height that is 5 to 10 times the zone width to have good diffraction efficiency. This high aspect ratio structuring is a very challenging field of nanofabrication. This diploma project has focused on improving the process step of fabricating the electroplating mold by cryo-cooling the polymer during the reactive ion etching with O2. The low temperature causes passivation of the sidewalls of the mold during etching which results in a more ideal rectangular profile of the high aspect ratio plating mold. By etching at -100 °C, structures with highly vertical sidewalls and no undercut were realized. The experiments showed that there is a tradeoff between the anisotropy of the zone profile and the formation rate of polymer residue, so-called RIE grass. Through a proper choice of process parameters the grass could be completely removed without introducing any undercut. / QC 20100414

Indiana University-Purdue University Indianapolis (IUPUI) / Etching of enamel caries lesions has been demonstrated to enhance remineralization. However, this effect reaches a plateau after a period of time. This study aimed at investigating the effectiveness of additional acid etching on remineralization. Forty 1 mm × 2 mm human enamel blocks with chemically induced artificial incipient lesions were used. Ten specimens were randomly selected at the end of demineralization for transverse microradiography (TMR) analysis. The remaining specimens were then divided into three groups (n = 10). Group A was remineralized by a pH cycling system with 1100 ppm sodium fluoride for 20 days. In group B, the specimens were etched with 35-percent phosphoric acid for 30 s and then remineralized. Group C was remineralized by same procedure as group B plus and given an additional acid etch after 10 days of remineralization. Mineral density was measured by x-ray microtomography (µ-CT). The volumetric mineral content [VM (µm3×105)] was determined between 91 and 0-wt%. The µ-CT % mineral recovery (%) was calculated using the formula 100×(remineralize VM - demineralization VM) / (sound VM - demineralization VM). One-hundred-μm sections of demineralized and remineralized specimens were used to assess the mineral loss (IML: vol%×µm) and lesion depth (µm) using TMR. The three groups showed no significant difference in mineral change or mineral content for µ-CT or TMR lesion depth. The TMR IML showed a significant difference between the demineralized specimens and the three remineralized groups. The correlation between TMR IML and TMR lesion depth was 0.66 (p < 0.0001). The µ-CT percent mineral recovery from demineralization was correlated with neither TMR IML nor TMR lesion depth. When evaluated with µ-CT, the twice-acid-etched group presented lower mineral gain values than the group etched only once with acid. Also, the twice-etched group presented lower mineral gain and greater TMR IML compared with the non-acid etch group. TMR images revealed reduction of surface layer in the acid-etched groups, especially in the twice-etched group, in which significant reduction or loss of surface layer occurred. Based on these results, we conclude that additional acid etching with 35-percent phosphoric acid does not enhance remineralization compared with a single application of acid etching. We believe that the viable existence of the surface layer is essential for remineralization of the lesion. Further investigations into the accuracy of µ-CT to detect minute mineral changes in incipient caries lesions are probably needed.

the presented work demonstrates the fabrication process of the master for nano-imprint lithography (NIL) stamp for multi-mode waveguide (MM-WG) with μ-mirror using hybrid-lithography, which includes a 2-photon-polymerization direct laser writing process (2PP-DLW) for μ-mirror surface and UV-photo lithography for MM-WGs. For the definition of the mirror surface at either end of waveguides in the master stamp, the 2PP-DLW process was used. It offers a lower surface roughness (< 0.1 λ) with fewer processing steps, alignment accuracy of ± 1 μm, prints fine and sharp contours, and relatively faster scanning for a specific material, which makes it the foremost technology over the traditional micro-mirror processes such as the dicing process, moving mask lithography, laser ablation, wet etching, and dry etching. For the fabrication of the waveguide core with rectangular cross-sections in the master stamp, UV mask exposure with SU-8 was used. It is a mass-production and low-cost technique. It gives a smooth structure with 90-degree sidewalls compared to other processes like dry etching, wet etching, mosquito method, and E-beam writing. We demonstrated the design and process of a master pattern with a density range from 0.04 to 0.2 to maintain equal pressure over the stamp in the NIL step for an almost uniform residual thickness layer.:Abstract Introduction Design of Experiments Experimental Results and Discussions Conclusion