Dépôt sous vide

Résumé

vignette|Chambre à vide de l'Observatoire du Mont Mégantic utilisée pour la re-aluminisation des miroirs de télescopes. Le dépôt sous vide est une technique de fabrication de couche mince : on cherche à déposer une couche de métal (la plupart du temps) sur une lame de substrat solide (verre ou silicium par exemple). Principe On y utilise le principe physique qui veut que, à très basse pression, les molécules (généralement monoatomiques) de vapeur d'un métal se déplacent avec très peu de risque de collision avec d'autres molécules : le gaz métallique se trouve projeté sur le substrat sans être freiné par les phénomènes de diffusion, et sans risque d'oxydation. La couche obtenue est ainsi très pure et très régulière. Le métal est chauffé au-dessus de sa température de fusion, mais loin de sa température d'ébullition sous pression normale. Le métal à déposer est placé dans un creuset en tungstène (dont la température de fusion est extrêmement élevée, ), lui-même placé sous la

Source officielle

https://fr.wikipedia.org/wiki/D%C3%A9p%C3%B4t_sous_vide

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Optimization of Sputter Deposition Process for Piezoelectric AlN Ultra-Thin Films

Kaitlin Marie Howell, Roman Welz

The sputtering conditions for the deposition of the layers underneath active AlN films were analyzed for improving the quality of the active AlN, and the dependence of AlN deposition temperature on crystalline quality was investigated, where a reduced deposition temperature could reduce the process time and cost. Therefore wafers with a 25 nm bottom electrode on a 15 nm adhesion layer, a 100 nm piezoelectric AlN films and a 100 nm top electrode have been deposited using different metals (Mo, Pt and Al) as bottom electrodes, different seed layers (Ti and AlN) and were deposited in two different sputtering machines. For the Mo bottom electrode, the sputtering power has also been varied between 250W, 500W, 750W and 1000W, and the deposition rates for these powers have been determined. The thickness, resistivity, rocking curve FWHM and stress have been measured for the bottom electrodes. The stress has been analyzed for the seed layers and for the AlN and top electrode layers and the rocking curve FWHM for the AlN has been measured and studied. Three structures with a Pt bottom electrode on a Ti seed layer have been created, where the active AlN films has been deposited at 300_C, 150_C and at room temperature respectively. It was shown, that AlN layers deposited on Pt bottom electrodes showed the best crystalline quality of the metals tested and the active AlN quality showed no significant difference, whether it was deposited at 150_C or 300_C.

2017

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Solid-on-liquid deposition (SOLID) techniques are of great interest to the MEMS and NEMS (Micro- and Nano Electro Mechanical Systems) community because of potential applications in biomedical engineering, on-chip liquid trapping, tunable micro-lenses, and replacements of gate oxides. However, depositing solids on liquid with subsequent hermetic sealing is difficult because liquids tend to have a lower density than solids. Furthermore, current systems seen in nature lack thermal, mechanical or chemical stability. Therefore, it is not surprising that liquids are not ubiquitous as functional layers in MEMS and NEMS. However, SOLID techniques have the potential to be harnessed and controlled for such systems because the gravitational force is negligible compared to surface tension, and therefore, the solid molecular precursors that typically condense on a liquid surface will not sediment into the fluid. In this review we summarize recent research into SOLID, where nucleation and subsequent cross-linking of solid precursors results in thin film growth on a liquid substrate. We describe a large variety of thin film deposition techniques such as thermal evaporation, sputtering, plasma enhanced chemical vapor deposition used to coat liquid substrates. Surprisingly, all attempts at deposition to date have been successful and a stable solid layer on a liquid can always be detected. However, all layers grown by non-equilibrium deposition processes showed a strong presence of wrinkles, presumably due to residual stress. In fact, the only example where no stress was observed is the deposition of parylene layers (poly-para-xylylene, PPX). Using all the experimental data analyzed to date we have been able to propose a simple model that predicts that the surface property of liquids at molecular level is influenced by cohesion forces between the liquid molecules. Finally, we conclude that the condensation of precursors from the gas phase is rather the rule and not the exception for SOLID techniques. (C) 2015 The Authors. Published by Elsevier B.V.

Elsevier2015

Chargement

Electrospray Ion Beam Deposition of Complex Non-Volatile Molecules

Gordon Rinke

The rational synthesis of novel materials requires the control over the arrangement of matter in order to meet the desired properties for applications and devices. Ultimately, control means to define the place of each atom and determine its chemical state, as well as being able to confirm the result in a measurement. Control at the atomic level can be achieved with scanning tunneling microscopy (STM), both in imaging and atomic manipulation. The latter, however, can never be used in meso- or even macroscopic material synthesis. Self-ordering phenomena determines atomic control in material synthesis as well, observed for instance in protein folding or in molecular beam epitaxy (MBE) technology. In both cases the atomically determined arrangement of the atoms in the structure is controlled only by environmental parameters that steer the self-ordering phenomena. In this thesis I show that electrospray ion beam deposition (ES-IBD) or ion soft-landing is a material processing technique, which combines and even extends the level of control offered by MBE. It is demonstrated that a vast range of complex organic materials including peptides and proteins is now available to ultrapure vacuum processing and moreover completely novel schemes of controlling self-ordering processes are provided. In-situ STM is applied to investigate the structure formation of complex molecules deposited by ES-IBD on well-defined, clean, and atomically flat surfaces in ultrahigh vacuum at the greatest detail. This allows us to explore the novel control features that are intrinsic to the ES-IBD deposition process like online coverage monitoring, deposition energy control, and mass-selection to select charge states or reactive species. The molecules studied here include organic molecular salts, dye molecules, reactive polymer building blocks, and finally peptides and proteins. Crystalline layer-by-layer as well as island growth was observed and revealed the equivalence to conventional MBE growth. On the basis of these deposition experiments the crucial influence of clusters in the ion beam for high material flux was discovered. Furthermore, it was found that the chemical state of the molecule is a key factor for the deposition result as chemical reactions can be induced or the self-assembly behavior can be altered. Alongside the capability to handle also extremely reactive molecules, the feasibility to control chemical reactions occurring as a result of an external stimulus to a specifically selected reactive species is demonstrated. Employing the control parameters that are specific to ES-IBD like charge state selection and deposition energy to complex biomolecules opens up new perspectives for vacuum deposition. In addition to the self-assembly governed by the molecule-substrate and molecule-molecule interaction, it was possible to actively steer the structure formation of proteins by influencing their stiffness and their reactivity through their charge state as well as by the deposition energy, parameters intrinsic to the ES-IBD method. Hence, electrospray ion beam deposition is indeed a tool to prepare well defined surface coatings at highest level of control and complexity. To be relevant for industrial applications, the performance of the system has to be further improved, most importantly in terms of deposition rate. In general, ES-IBD enables new approaches for the growth of functional coatings but also serving as perfect sample preparation tool for the characterization of complex molecules on the atomic scale by scanning probe or more general surface science methods.

EPFL2013

Chargement

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Elsevier2015

Electrospray Ion Beam Deposition of Complex Non-Volatile Molecules

Gordon Rinke

EPFL2013