Plasma interaction with low – k Silsesquioxane materiels

Low – κ dielectric materials play a very important role in the fabrication of integrated circuits (IC). Materials with a very low dielectric constant are necessary for use as inter layer dielectrics (ILDs), because they increase the efficiency of the ICs by reducing the resistance capacitance delays and power consumption of the circuits. This thesis presents the deposition and characterisation of Silsesquioxane (SSQ) materials, particularly Methyl Silsesquioxane (MSQ) and Poly Phenyl Methyl Silsesquioxane (PMSQ) thin films by spin coating and subsequent annealing. The changes to the film post plasma exposure were studied using a wide range of characterisation techniques such as spectroscopic ellipsometry, stylus profilometry, FTIR, TGA, water contact angle measurement, XPS, AFM, SEM, EDX, AFM, dielectric constant measurement of the thin films, etc. The study on MSQ films were carried out to have a better understanding of film deposition, processing, and characterisation techniques as these studies are widely reported in literature because of its use as an ILD material. The deposited MSQ thin films had a κ - value of ~ 2.6 ± 0.1. Significant increase in the κ - value was observed upon exposure of these films to SF6 and O2 plasmas due to the deteriorating effect of the plasma on the films. Deposited PMSQ thin films had a κ - value of ~ 2.7 ± 0.1 and they did not show any considerable variation in their κ - value upon exposure to SF6 and O2 plasmas, even though significant erosion of the PMSQ film was observed during the exposure of the film to SF6 plasma. Modern day electronics require materials with very low dielectric constants for optimal performance. Several approaches are used commercially to further reduce the κ – value of dielectric materials used for ILD applications. Porosity was introduced into the vi PMSQ thin films by sacrificial porogen technique to further reduce the dielectric constant of the thin films using Heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin (tCD) as the porogen material. Changes in the PMSQ films due to the introduction of porosity were studied which showed a reduction in the density and the κ – value of the film. A reduction of ~ 25% in density was observed in the XRR measurements of the porous films and the κ – value of the films were reduced by ~ 20% from κ = 2.7 ±0.1 to κ = 2.2 ±0.1 by the introduction of porosity. The effect of plasma exposure on the porous PMSQ films resulted in an increase in the dielectric constant of the porous material. The thesis also analyses the expected variations in the film density and κ-value and compares it with the observed density and κ-value. It also calculates a rough estimate of the change in the surface area of the film as a result of porosity integration. Experimental demonstrations of a novel method to pattern the dielectric film surface namely Nano sphere Lithography is presented in the final section of this thesis

Démonstration de l'intérêt des dispositifs multi-grilles auto-alignées pour les noeuds sub-10nm.

Les nombreuses modifications de la structure du transistor bulk ont permis de poursuivre la miniaturisation jusqu'à sa limite aux nœuds 32/28nm. Les technologies actuelles répondent au besoin d'un meilleur contrôle électrostatique en s'ouvrant vers l'industrialisation de transistors complètement dépletés, avec les architectures sur film mince (FDSOI) ou non planaires (TriGate FinFET bulk). Dans ce dernier cas, le substrat bulk reste limitant pour des applications à basse consommation. La combinaison de la technologie SOI et d'une architecture non-planaire conduit aux transistors TriGate sur SOI (ou TGSOI). Nous verrons l'intérêt de ces dispositifs et démontrerons qu'ils sont compatibles avec les techniques de contrainte. On montrera en particulier les améliorations de mobilité et de courants obtenus sur ces dispositifs de largeur inférieure à 15nm. Des simulations montrent également qu'un dispositif TGSOI peut être compatible avec les techniques de modulation de VT. Enfin, nous démontrons la possibilité de fabriquer des dispositifs ultimes à nanofils empilés avec une grille enrobante par une technique innovante de lithographie tridimensionnelle. La conception, la caractérisation physique et les premiers résultats électriques obtenus seront présentés. Ces solutions peuvent répondre aux besoins des nœuds sub-10nm.Changing the bulk transistor structure was sufficient so far to fulfill the scaling needs. The current technologies answer the needs of electrostatics control with the industrialization of fully depleted transistors, with thin-film (FDSOI) or non-planar (TriGate FinFet bulk) technologies. In the latter, bulk substrate is still an issue for low power applications. Combining SOI with multiple-gate structure gives rise to TriGate on SOI (or TGSOI). We will discuss the interest of such devices and will demonstrate their compatibility with strain techniques. We will focus on the mobility and current enhancement obtained on sub-15nm width devices. Simulations also demonstrate the compatibility of TGSOI with VT modulation technique. Finally, we demonstrate the fabrication through 3D lithography of ultimate stacked nanowires with a gate-all-around. The conception, physical characterization and first electrical results are presented.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

The theoretical and experimental exploration of the use of predatory bacteria to control biofilms

Membrane based technologies are widely used for treating drinking water in sparsely populated areas, but their effectiveness is significantly diminished by the growth of biofilms and biofouling. Preventing or removing biofilms can increase the life span of membranes and, thus, improve their economic viability. Most cleaning methods involve physical disruption or antimicrobial chemicals and, therefore, require an interruption in the membrane operation. Bdellovibrio, a group of predatory bacteria, are a potential alternative to antimicrobials or physical disruption because of its ability to kill a large range of gram-negative bacterial prey and the inability of their prey to develop genetic resistance. However, the use of Bdellovibrio in industrial application has not been widespread in part due to the lack of understanding of the dynamics between Bdellovibrio and their prey. To compound this, many of the previous investigations into Bdellovibrio and biofilm ecology are limited by inaccurate, uninformative, and labour-intensive methods to quantify the population dynamics, which makes it difficult to build comprehensive models to exploit Bdellovibrio as a control to biofilms in systems like drinking water membranes. This thesis aims to develop a set of novel methods and technologies to accurately investigate Bdellovibrio and the effect they have on dynamics of their prey; Pseudomonas sp, a key gram negative biofilm forming species. This research develops the first protocol to use flow cytometry to accurately and rapidly quantify Bdellovibrio and Pseudomonas sp growth, which makes recording high resolution population dynamics feasible. The protocol was used for the development and experimental validation of mathematical models which aimed to predict Bdellovibrio dynamics in batch and chemostat systems. We show the first experimental observation of Bdellovibrio-prey oscillations, a key component of predation dynamics and a desired phenomenon for the use of Bdellovibrio as a self-sustaining biocontrol. To extend the models for application to systems where biofilms prevail, we demonstrated a new method of deploying flow cytometry and fluorescent assays to quantify and characterise the effect of nutrients on biofilm growth and predation. The findings suggest that extracellular polymeric substances (EPS) play a vital role in the attachment and persistence of biofilm when under Bdellovibrio predation. Thus, in biofilm research, the simple density dependent predator-prey interactions need to be augmented by representing the spatial heterogeneities in biofilm processes and properties such as its detachment, EPS and presence of metabolically damaged cells. For a more nuanced analysis of predator-prey interactions, at the resolution of individual organisms, this research develops a novel microfluidic device to observe Bdellovibrio predation on a 1-D biofilm. This thesis describes both the rationale and novel protocols for combining electron-beam lithography with, the more commonly used, photolithography to create an array of high-resolution channels to constrain biofilms and challenge them with predators. The research demonstrates the opportunities and the technical challenges in using microfluidics. Ultimately, if we are to develop mathematical models that can be parameterised and used effectively in designing strategies for controlling biofilms using predatory bacteria, then observations at the individual scale in microfluidic devices will be invaluable