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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

ECR Assisted Deposition of Tin And Si3N4 Thin Films For Microelectronic Applications

Vargheese, K Deenamma 07 1900 (has links)
The broad theme of the present research investigation is Ion Assisted Deposition of thin films and its effect on the properties of thin films. Though this activity has been of interest to researchers for more than a decade, the development of different types of ion sources with control over the ion flux and energy, makes it a current topic of interest. Ion assisted deposition was successful in depositing thin films of many material with desired qualities, however, there are certain class of materials whose deposition has been rather difficult. This has mainly been attributed to higher energies and low ion flux of conventional ion sources. The advent of ECR ion sources for thin film deposition has given impetus to the deposition of such materials. This is due to the low energy high-density plasma generated in this type of sources. Hitherto, these sources were widely used in PECVD techniques and only recently the importance of ECR sources in PVD techniques has been realized. This thesis is on the development of ECR plasma source for ion assisted deposition of thin films using PVD techniques. This thesis is organized into six chapters. The first chapter gives an introduction on the ion assisted growth of thin films and the importance of ECR plasma. A detailed discussion on various aspects of ECR sources has been included. The design details on the development of ECR source have been discussed in the second chapter. The performance of ECR source as analyzed by the Langmuir probe are also discussed. Variation of plasma parameters like ion density, electron temperature, plasma potential and floating potential as a function of pressure and microwave power have been studied using Langmuir probe analysis. An ion density of the order of 1011/cm3 was measured at a distance of 8 cm from the plasma source with a microwave power of 400 watts. This was comparable to the ion density reported in downstream plasma of ECR sources. The behavior of plasma parameters with variation in microwave power and pressure was explained on the basis of microwave transmission above critical ion density and the microwave power absorption. The uniformity of the plasma parameters at the substrate position (29 cm from the ECR source) was found to be ± 2% over a diameter of 12 cm, which makes the ion source suitable for ion assisted deposition. The third chapter deals with the simulation and experimental study of the ECR sputtering process. ECR sputter type sources are equipped with cylindrical targets. The sputtered flux distribution on the substrate depends on target geometry, sputtering pressure and target-substrate distance. The effect of cylindrical geometry on the distribution of sputtered flux has been simulated by Monte Carlo methods. It is found that the sputtered flux distribution at different pressures and target-substrate distances in ECR sputter type source differs from the conventional glow discharge sputtering system equipped with planar targets. The simulated results are compared with the experimental results. The simulated data agree very well with the experimental data. The deposition and characterization of the TiN thin films for diffusion barrier applications in copper metallization have been discussed in the fourth chapter. Titanium nitride films are prepared by ECR sputtering. The effect of high density ion bombardment on the morphology, orientation and resistivity of the films was studied. It was observed that films with atomic smoothness could be prepared by ECR sputtering. Also the high density ion bombardment has been found to be effective for the film growth in (100) orientation. The behavior of TiN films deposited by this method as a diffusion barrier in copper metallization has been investigated. The resistivity measurements and RBS depth profile studies showed that up to 700°C there is no diffusion of copper into silicon. This shows that ECR sputtered TiN can be used as an effective diffusion barrier in copper metallization. The fifth chapter contains investigations on the ECR assisted growth of silicon nitride films. The films are characterized for composition, morphology and chemical bonding using AES, RBS, AFM, XPS and FTIR. AFM studies revealed that ion bombardment results in the reduction of surface roughness, which indicates dense film growth. The effect of ion assistance on the optical and electrical properties is studied in detail. Films prepared with microwave power ranging from 100 to 200 watts are having bandgap and refractive index of 4.9 eV and 1.92 respectively. Interface state density of silicon nitride films prepared in the above mentioned range was found to be 5x10 10 eVcm2. These films exhibited a resistivity of 10 13 Ω, cm and critical field of 4 MV/cm. The electrical conductivity in these films has been explained on the basis of Poole and Frenkel conduction. The low value of interface state density, higher resistivity, and critical field show that good quality SiN4 films can be deposited with low energy high density ECR plasma. A detailed summary of this research investigation has been discussed in the last chapter. The thesis is concluded with a discussion on the need of focused ECR source to establish ECR assisted deposition as a versatile technique for the growth of thin films.
42

A study of the structure and dynamics of Saturn's inner plasma disk

Holmberg, Mika January 2015 (has links)
This thesis presents a study of the inner plasma disk of Saturn. The results are derived from measurements by the instruments on board the Cassini spacecraft, mainly the Cassini Langmuir probe (LP), which has been in orbit around Saturn since 2004. One of the great discoveries of the Cassini spacecraft is that the Saturnian moon Enceladus, located at 3.95 Saturn radii (1 RS = 60,268 km), constantly expels water vapor and condensed water from ridges and troughs located in its south polar region. Impact ionization and photoionization of the water molecules, and subsequent transport, creates a plasma disk around the orbit of Enceladus. The plasma disk ion components are mainly hydrogen ions H+ and water group ions W+ (O+, OH+, H2O+, and H3O+). The Cassini LP is used to measure the properties of the plasma. A new method to derive ion density and ion velocity from Langmuir probe measurements has been developed. The estimated LP statistics are used to derive the extension of the plasma disk, which show plasma densities above ~20 cm-3 in between 2.7 and 8.8 RS. The densities also show a very variable plasma disk, varying with one order of magnitude at the inner part of the disk. We show that the density variation could partly be explained by a dayside/nightside asymmetry in both equatorial ion densities and azimuthal ion velocities. The asymmetry is suggested to be due to the particle orbits being shifted towards the Sun that in turn would cause the whole plasma disk to be shifted. We also investigate the ion loss processes of the inner plasma disk and conclude that loss by transport dominates loss by recombination in the entire region. However, loss by recombination is still important in the region closest to Enceladus (~±0.5 RS) where it differs with only a factor of two from ion transport loss.
43

Plasmaphysikalische Charakterisierung einer magnetfeldgestützten Hohlkathoden-Bogenentladung und ihre Anwendung in der Vakuumbeschichtung

Zimmermann, Burkhard 07 March 2013 (has links) (PDF)
Die vorliegende Dissertation behandelt Charakterisierung, Modellbildung sowie Anwendung einer magnetfeldgestützten Hohlkathoden-Bogenentladung. Hohlkathoden sind seit den 1960er Jahren Gegenstand grundlagen- sowie anwendungsorientierter Forschung und werden seit 20 Jahren am Fraunhofer-Institut für Elektronenstrahl- und Plasmatechnik für die Anwendung auf dem Gebiet der Vakuumbeschichtung weiterentwickelt. Ziel dieser Arbeit ist es, die technologischen Fortschritte physikalisch zu verstehen und gezielte Weiterentwicklungen für spezifische Einsatzgebiete zu ermöglichen. In der untersuchten Hohlkathodenbauform ist das aus Tantal bestehende, vom Arbeitsgas Argon durchströmte Kathodenröhrchen koaxial von einer Ringanode sowie von einer Magnetfeldspule umgeben. Die Entladung wird durch Hochspannungspulse gezündet, worauf sich ein diffuser Bogen im Röhrchen (internes Plasma) ausbildet. Das Röhrchen wird von Plasmaionen auf hohe Temperaturen geheizt, die eine thermionische Emission von Elektronen ermöglichen, welche das Plasma speisen. Das technologisch nutzbare externe Plasma wird im Vakuumrezipienten durch Wechselwirkung der Gasteilchen mit Strahlelektronen aus der Kathode erzeugt. Bei starker Reduktion des Arbeitsgasflusses wird die Entladung durch das Magnetfeld der Spule stabilisiert. Der experimentelle Befund, dass dadurch Plasmadichte und -reichweite sowie ggf. die Ladungsträgerenergien im Rezipienten aufgrund des intensiveren Elektronenstrahls wesentlich gesteigert werden können, wird durch ortsaufgelöste Langmuir-Sondenmessung, optische Emissionsspektroskopie und energieaufgelöste Massenspektrometrie ausführlich belegt und nach der Lösung von Strom- und Wärmebilanzgleichungen durch die Verhältnisse im Kathodenröhrchen begründet. Neben Argon werden auch typische Reaktivgase der Vakuumbeschichtung im Hohlkathodenplasma betrachtet: zum einen Stickstoff und Sauerstoff, die in reaktiven PVD-Prozessen (physikalische Dampfphasenabscheidung) zur Beschichtung mit Oxid- bzw. Nitridschichten zum Einsatz kommen und durch Ionisation, Dissoziation und Anregung im Hohlkathodenplasma verbesserte Schichteigenschaften ermöglichen; zum anderen Azetylen, das bei PECVD (plasmagestützte chemische Dampfphasenabscheidung) von amorphen wasserstoffhaltigen Kohlenstoffschichten z. B. für tribologische oder biokompatible Beschichtungen genutzt wird. Azetylen wird durch Streuprozesse mit Elektronen und Ionen im Plasma aufgespalten, wodurch schichtbildende Spezies erzeugt werden, die am Substrat kondensieren. Durch die Wahl der Plasmaparameter sowie durch abgestimmte Substratbiasspannung und Substratkühlung lassen sich die Beschichtungsrate einstellen sowie polymer-, graphit- oder diamantartige Eigenschaften erzielen. Neben der Plasmadiagnostik mittels energieaufgelöster Massenspektrometrie werden die erzeugten Kohlenstoffschichten vorgestellt und hinsichtlich Härte, Zusammensetzung und Morphologie analysiert. / In the present thesis, characterization, modeling and application of a magnetically enhanced hollow cathode arc discharge are presented. Since the 1960s, hollow cathodes are being studied in basic and applied research. At Fraunhofer Institute for Electron Beam and Plasma Technology, further development concerning the application in vacuum coating technology has been carried out for about twenty years. The present work targets on physically understanding the technological progress in order to enable specific further development and application. In the investigated hollow cathode device, a ring-shaped anode and a magnetic field coil are arranged coaxially around the tantalum cathode tube, which is flown through by argon as the working gas. The discharge is ignited by high voltage pulses establishing a diffuse arc within the cathode tube (internal plasma). The cathode is being heated by the plasma ions to high temperatures, which leads to thermionic emission of electrons sustaining the plasma. The external plasma in the vacuum chamber, which can be used for technological applications, is generated by collisions of gas atoms with beam electrons originating from the cathode. In the case of strongly reduced working gas flow, the discharge is stabilized by the magnetic field of the coil; the related experimental findings such as significantly increased plasma density and range as well as higher charge carrier energies in the external plasma are extensively proved by spatially resolved Langmuir probe measurements, optical emission spectroscopy, and energy-resolved ion mass spectrometry. Furthermore, the results are correlated to the conditions within the cathode tube by solving the current and heat balance equations. Besides argon, typical reactive gases used in vacuum coating are examined in the hollow cathode plasma, too. First, nitrogen and oxygen, which are applied in PVD (physical vapor deposition) processes for the deposition of oxide and nitride layers, are ionized, dissociated, and excited by plasma processes. In the case of practical application, this plasma activation leads to improved film properties. Second, acetylene is used as a precursor for PECVD (plasma-enhanced chemical vapor deposition) of amorphous hydrogenated carbon films, e.g. for tribological or biocompatible applications. Acetylene is cracked by electron and ion scattering in the plasma providing film-forming species to be deposited on the substrate. The deposition rate as well as the polymeric, graphitic, or diamond-like properties can be controlled by plasma parameters, a defined substrate bias, and substrate cooling. The hollow cathode-generated acetylene plasma has been characterized by energy-resolved ion mass spectrometry, and the carbon films obtained are analyzed regarding hardness, film composition, and morphology.
44

The Non-uniform Argon Dc Glow Discharge System Parameters Measured With Fast Three Couples Of Double Probe

Akbar, Demiral Salih 01 March 2006 (has links) (PDF)
The non-uniform dc glow discharge plasma system is studied by using isolated computer controlled three couples of double probe system (TCDP) in argon gas, simultaneously. TCDP system has been developed to use for magnetized, unmagnetized, and for low oscillating plasma systems by using low pass filter with optically isolated circuitry to minimize the measurement errors with higher resolution and accuracy. Difference in the shapes and diameters of the discharge tube from region to region leads to change in the positive column glow discharge properties. This is because the positive column inhomogeneities, rising from the increase in the electron densities at the small tube radius region than the large one. Therefore, the axial electric field and the electron temperature have been diverted from their normal behavior in the positive column. However, at the large radius regions, the axial electric field seams to stay approximately constant at higher discharge currents. On the other hand, In this work the radial dependence of the electron temperature, density, floating potential, and the normalized probe radius (&amp / #958 / =rp&amp / #955 / D) has been investigated. Since, the probe radius is smaller than Debye length, the orbital motion limited (OML) theory has been used. As a result, the electron temperature (at the center) decreased and density increased with decreasing tube radius, and they have maximum values at the first probe (near the cathode). The electron density ne was observed to decrease and electron temperature Te to increase with increasing the discharge current. The floating potential has less negative value with decreasing tube radius except at the higher currents. Finally, it has been found that the &amp / #958 / is proportional with electron density, but it remains constant depending on the value of Te and ne.
45

Fundamental Analysis of the Interaction of Low Pressure Plasmas with Polymer Surfaces

Bach, Markus 25 November 2003 (has links)
The treatment of polymer surfaces by low pressure plasmas is of technological interest in a variety of applications for modification and functionalisation. Until now the interactions of the individual plasma species (especially electrons) with polymeric material have not been subject of a microscopic study.In an anticipated chapter the inner plasma parameters were characterised by Langmuir probe measurements, leading to a precise knowledge about the density and energy distributions of plasma electrons and ions. The values for electrons were later used for an exclusive treatment with this species. The main part of this thesis describes and interprets the chemical composition after UV, plasma and electron treatment by x-ray photoelectron spectroscopy (XPS), structural changes by atomic force microscopy (AFM) and their combination to distinguish the fundamental interactions with polyethylene and polypropylene surfaces. It was found that all treatments show specific modification behaviour according to the chemical composition, topography and modification depth. For an argon microwave discharge, the plasma effects can also be obtained by a combination of UV and electron treatment. Fundamental radical reactions have been traced indirectly by chemical derivatisation as well as their passivation reactions through cross-linkage and the creation of double bonds.
46

Investigation of thrust mechanisms in a water fed pulsed plasma thruster

Scharlemann, Carsten A. January 2003 (has links)
No description available.
47

Etude des effets de gaine induites par une antenne de chauffage à la fréquence cyclotronique ionique (FCI, 30-80 MHz) et de leur impact sur les mesures par sondes dans les plasmas de fusion / Study of sheath effects induced by an heating Ion Cyclotron Radio Frequency antenna (ICRF, 30-80MHz) and their impact to probe measurements in fusion plasma devices

Ngadjeu Djomzoue, Alain narcisse 16 December 2010 (has links)
Ces travaux abordent la problématique des mesures de sonde de Langmuir dans un environnement RF. Les mesures expérimentales ont montré que des courants DC négatifs (électroniques) étaient collectés sur la structure d'une antenne ICRF sous tension, pendant que des courants DC positifs (ioniques) sont recueillis par une sonde de Langmuir à l'autre bout du tube de flux magnétique ouvert connecté à l'antenne, la sonde étant au potentiel de la machine. Un modèle de tube de flux asymétrique, de type de sonde double, est présenté. Celui-ci modélise un plasma, confiné le long des lignes de champ magnétique, ayant à chaque extrémité une électrode dont l'une est polarisée à un potentiel RF et l'autre à la masse. L'électrode polarisée modélise le potentiel RF résultant de l'intégration, le long d'une ligne champ magnétique, du champ électrique rayonné par les straps d'une antenne ICRF, tandis que l'autre électrode modélise la sonde au potentiel de la machine. Ce modèle permet d'expliquer l'apparition de courants DC en émettant simplement l'hypothèse qu'il faut à la fois une asymétrie de la source RF par rapport à une masse fixe, une conductivité RF transverse non nulle autorisant des courants RF transverses ainsi qu'une caractéristique courant-tension non linéaire due aux gaines pour favoriser des courants négatifs du côté RF et des courants positifs côté sonde. Ce modèle permet également de modéliser les caractéristiques Courant DC - Tension DC d'une sonde en présence de RF et ainsi d'évaluer les propriétés du plasma. Dans ce cas l'électrode modélisant la sonde n'est plus à la masse, mais à un potentiel donné. Des résultats analytiques sont trouvés dans certaines limites / This work investigates the problematic of probe measurements in RF environment. DC currents flowing along magnetic field lines connected to powered ICRF antennas have been observed experimentally. Negative (i.e. net electron) current is collected on the powered ICRF antenna structure, while positive (i.e. net ion) current is collected by magnetically connected Langmuir probes. An asymmetric model based upon a double probe configuration was developed. The ICRF near field effect is mimicked by a ?driven? RF electrode at one extremity of an "active" open magnetic flux tube, where a purely sinusoidal potential is imposed. The other connection point is maintained at ground potential to model a collecting probe. This "active" flux tube can exchange transverse RF currents with surrounding "passive" tubes, whose extremities are grounded. With simple assumptions, an analytical solution is obtained. We can thus explain how DC currents are produced from RF sheaths. This model also makes it possible to model the characteristics DC Current' DC Voltage of a probe in the presence of RF and thus to evaluate some plasma properties. In this case the electrode at ground potential (probe) is polarized at a given potential. Analytical results are found within certain limits
48

Modélisation et contrôle hamiltonien du transport radial dans les plasmas magnétisés à configuration linéaire

Izacard, Olivier 28 October 2011 (has links)
Dans l'optique de produire de l'énergie à travers les réactions de fusion, nous sommes amenés à étudier des phénomènes physiques qui ont lieux dans les tokamaks. Les instabilités qui existent dans les tokamaks peuvent fortement dégrader le confinement et ont un impacte sur le fonctionnement de futurs réactions à fusion. Des mesures révèlent un fort transport radial. Même si ce transport radial est en partie est une conséquence des collisions, l'instabilité d'interchange est la source dominante à ce transport puisque le type de plasmas nous intéressant sont faiblement collisionnels. Dans la limite non collisionnelle, la description hamiltonienne permet de décrire le système dynamique des particules du plasmas dans un champ électromagnétique. Nous donnons de l'importance à cette description afin de pouvoir accéder aux outils hamiltoniens.Nous travaillons sur la modélisation et le contrôle hamiltonien du transport radial. Après avoir écrit le modèle hamiltonien des particules d'un plasma magnétisé, nous introduisons les réductions de ce modèle lagrangien en modèles eulériens réduits afin de s'adapter à certains calculs numériques et théoriques. Ces réductions donnent lieux aux équations fluides hamiltonien. Cependant, nous montrons que ces réductions peuvent faire perdre la propriété hamiltonienne. En particulier pour obtenir un modèle ayant la température des ions (puisqu'elle n'est pas négligeable au centre du plasma), nous montrons la procédure conservant la propriété hamiltonienne à partir du modèle sans température des ions.Quant à l'étude du transport radial, nous appliquons une des propriétés hamiltoniennes (le contrôle) afin de créer une barrière de transport par des perturbations du système. Nous étudions de manière idéale l'effet du contrôle à travers la dynamique lagrangienne des traceurs appelés particules test. Nous faisons particulièrement des efforts dans la prise en compte des contraintes numériques et expérimentales. Nous montrons notamment la robustesse du contrôle lors de l'application des perturbations par des sondes de Langmuir.Finalement, nous étudions l'application du contrôle dans un modèle eulérien décrivant la rétroaction du plasmas (à travers la densité et le potentiel électrique) lorsque nous appliquons les perturbations. Cette étape permet de prendre en compte le couplage du système plasma-perturbations. En utilisant un code fluide permettant de décrire le plasma de bord lors de perturbations générées par des sondes de Langmuir. Nous développons un algorithme permettant de calculer le contrôle en tout temps en fonction du potentiel électrique. Nous montrons alors que la valeur moyenne du potentiel électrique joue un rôle important pour l'application du contrôle dans un modèle fluide. / In order to produce energy through fusion reactions, we are led to study of physical phenomena that occur in tokamaks. The instabilities that exist in tokamaks can significantly degrade the confinement and have an impact on the operation of future fusion reactors. Measurements reveal a strong radial transport. Although this is partly a consequence of collisions, the interchange instability is the dominant source to transport since the type of plasmas that interest us are weakly collisional. Within non collisional limit, the Hamiltonian description used to describe the dynamical system of charged particles in an electromagnetic field. We give importance to this description in order to access the Hamiltonian tools.We are working on modeling and control Hamiltonian of radial transport. After writing the Hamiltonian model of particles in a magnetized plasma, we introduced some reductions from Lagrangian models to Eulerian reduced models in order to accommodate some theoretical and numerical calculations. These places give the Hamiltonian fluid equations. However, we show that these reductions may lose the Hamiltonian property. In particular for a model with the ion temperature (not neglected at the center of the plasma), we show the procedure preserving the Hamiltonian property from the model without ion temperature.As for the study of radial transport, we apply one of the Hamiltonian properties (the control) to create a transport barrier by perturbations of the system. We are looking ideally the effect of control through the Lagrangian dynamics of tracers called test particles. We make particular efforts in the consideration of numerical and experimental constraints. We show the robustness of control when applying perturbations by Langmuir probes.Finally, we study the application of control in an Eulerian model describing the feedback of plasma (through the density and the electric potential) when we apply the perturbations. This step allows to take into account the coupling of the system plasma-perturbations. We use a numerical code to describe the plasma at the edge during perturbations generated by Langmuir probes. We develop an algorithm to calculate the control at all times depending on the electric potential. Finally we show that the average value of electric potential plays an important role in the implementation of control in a fluid model.
49

Untersuchung der Transportphänome magnetiserter Plasmen in der Umgebung materieller Limiter

Waldmann, Ole 21 July 2009 (has links)
Es wurden die Transportphänomene magnetisierter Plasmen in der Umgebung materieller Limiter am linearen Plasmagenerator PSI-2 unter Verwendung von elektrischen und optischen Diagnostiken untersucht. Der Senkrechtdiffusionskoeffizient wurde mit D= 5 m^2/s und einer 1/B-Abhängigkeit bestimmt. Der dominierende Prozess des Radialtransportes ist turbulenter Natur. Unter Berücksichtigung der Volumenionisation kann das radiale Dichteprofil konsistent beschrieben werden. Der Schaft einer Langmuirsonde reduziert in einem magnetisierten Plasma die Elektronendichte. Dieses wurde mit zwei Sonden untersucht. Es wird eine globale Teilchenbilanz vorgestellt, die diese Reduktion beschreibt. Bringt man einen Limiter in ein strömendes magnetisiertes Plasma ein, so bildet sich hinter diesem ein Schatten aus. Vor dem Limiter zeigt sich für einige Plasmaregime ein inverser Schatten. Beide sind durch die starke Abhängigkeit der Emissivität von der Elektronentemperatur zu erklären. Ortsaufgelöste Messungen mit Langmuirsonden und optischer Spektroskopie bestätigen dieses experimentell und zeigen kurze Skalenlängen der Dichte für den Abfall vor und den Anstieg hinter einem Limiter. Die Längen zeigen keine klare Skalierung mit dem Ionengyrationsradius. Es werden ortsaufgelöste Messungen der Plasmaparameter mit einer Langmuirsonde vor einem Limiter unter schrägem Einfall vorgestellt. In Wasserstoffplasmen lässt sich der Dichteverlauf mit dem Modell von Chodura [Cho:82] gut beschreiben. In einer stationären Bogenentladung sind Fluktuationen in der Entladungsspannung zu finden. Diese Fluktuationen erzeugen suprathermische Elektronen, die von Limitern geblockt werden. Durch das Einbringen von Limitern werden turbulente räumliche Strukturen erzeugt, die in das Schattengebiet eindringen. Diese sind sowohl optisch mit Photomultipliern als auch als Fluktuation des Ionensättigungsstromes einer Langmuirsonde nachweisbar. Die Strukturen können den Quertransport in den Plasmaschatten verstärken. / The transport phenomena of magnetized plasmas in the vicinity of a material limiter have been investigated. The investigations were carried out at the linear plasma generator PSI-2 with electrical and optical diagnostics. The perpendicular diffusion coefficient was determined as D= 5 m^2/s with a magnetic field dependence of 1/B. The dominant process of the radial transport is therefore anomalous. By consideration of volume ionization the radial density profile can be consistently described. The shaft of a Langmuir probe acts as a particle sink and reduces electron density. This was investigated using two probes. The reduction can be explained in terms of a global particle model. On immersing a limiter into a streaming, magnetized plasma a distinct shadow region is observed downstream of the target. In addition, for some plasma conditions the region upstream of the target forms an inverse shadow. Both observations can be explained by the strong dependence of the emissivity on electron temperature. This is confirmed experimentally by Langmuir probes and optical spectroscopy. Spatially resolved measurements reveal short scale lengths for a decrease of density in front of and an increase behind a limiter. These lengths do not clearly scale with the ion gyroradius. Spatially resolved Langmuir probe measurements taken in front of a limiter at oblique incidence are presented. For hydrogen plasmas the model of Chodura [Cho:82] describes the density profile quite well. In a stationary arc discharge fluctuations in the discharge voltage are found. The fluctuations produce suprathermal electrons. These electrons are blocked by limiters. A limited plasma produces turbulent spatial structures which penetrate into the shadow region. These structures can be detected with photomultipliers and also as a fluctuation in the ion saturation current of a Langmuir probe. They can enhance perpendicular transport into the plasma shadow.
50

Caractérisation expérimentale et optimisation de procédés plasma pour la décontamination de l'AMC (Contamination Moléculaire Aéroportée) / Experimental characterization and optimization of plasma processes for the decontamination of the AMC (Airborne Molecular Contamination)

Laurent, Christopher 19 December 2016 (has links)
Un problème majeur en microélectronique est la contamination moléculaire aéroportée qui dégrade les substrats et les masques diminuant le rendement de production des composants. L'utilisation de boîtes de transport en polymères pour le stockage des substrats favorise la contamination moléculaire croisée entre les deux éléments. Il est alors primordial d'avoir un procédé de décontamination des boîtes efficace et rapide. Dans le cadre de cette thèse, plusieurs solutions de décontamination par plasmas ont été étudiées. Les plasmas étaient générés selon quatre couplages énergétiques en utilisant des excitations radiofréquence (13,56 MHz) et micro-onde (2,45 GHz). Ils étaient caractérisés avec une sonde de Langmuir et un spectromètre optique sous différentes conditions expérimentales. Enfin, un protocole de contamination au fluorure d'hydrogène a été développé pour évaluer et comparer l'efficacité de décontamination des procédés plasma à ceux utilisés actuellement en microélectronique. / Un problème majeur en microélectronique est la contamination moléculaire aéroportée qui dégrade les substrats et les masques diminuant le rendement de production des composants. L'utilisation de boîtes de transport en polymères pour le stockage des substrats favorise la contamination moléculaire croisée entre les deux éléments. Il est alors primordial d'avoir un procédé de décontamination des boîtes efficace et rapide. Dans le cadre de cette thèse, plusieurs solutions de décontamination par plasmas ont été étudiées. Les plasmas étaient générés selon quatre couplages énergétiques en utilisant des excitations radiofréquence (13,56 MHz) et micro-onde (2,45 GHz). Ils étaient caractérisés avec une sonde de Langmuir et un spectromètre optique sous différentes conditions expérimentales. Enfin, un protocole de contamination au fluorure d'hydrogène a été développé pour évaluer et comparer l'efficacité de décontamination des procédés plasma à ceux utilisés actuellement en microélectronique.

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