Experimental study and kinetic modelling of chemical vapor deposition process of silicon oxide and oxynitride thin films for aqueous corrosion barriers

The deposition of silica-based materials is widely used in numerous industrial sectors, including microelectronics, food packaging, gas separation and pharmaceutics. Depending on the targetapplication, these materials are required to fulfil specific requirements in terms of mechanical properties, durability, and composition. The implementation of such coatings in pharmaceutics applications require, more specifically, good aqueous barrier and anti-diffusion properties, as well as effective corrosion resistance. The hydrolytic resistance and the durability of the coatings is directly linked to the level of densification of the ceramic network. In the case of amorphous SiO2, an improved network cross-linking, and by consequence densification, can be induced through the partial replacement of the O2- anions by N3- (or C4-) ones, producing denser amorphous silicon oxynitride (SiOxNy) or silicon oxycarbide (SiOxCy) coatings that can meet the performance requirements dictated by the various pharmaceutical applications. However, very little information is available in the literature concerning the deposition of SiOxNy coatings in accordance to the application-specific constraints: namely the production of chemically inert films on complex, 3D substrates, deposited at atmospheric pressure and at moderate temperatures (<570°C), with high deposition rates. To achieve the above goals, the deposition of amorphous silica-based films is undertaken via the utilization of a thermal CVD process defined around reactive, novel chemistries. The reactive chemical pathways aids in the production of SiOxNy at temperatures lower than the conventional ones, and more importantly, compatible with thermosensitive substrates. The gradual increase in N and C contents in the deposits is carried out through carefully selected precursor molecules and reagent gas compositions. Innovative deposition routes, based on single or dual-precursor combinations of classic silicon-containing precursors such as tetraethylorthosilicate (TEOS) or hexamethyldisilazane (HMDS), and more novel compounds such as tris(dimethylsilyl)amine (TDMSA) are explored. Since the progressive incorporation of nitrogen and carbon in the films is at the core of this work, the resulting evolution of the silicate network is extensively studied through physicochemical, structural and mechanical characterization protocols. A multidisciplinary approach is embraced, combining materials science, analytical chemistry and process engineering in a way that involves the simultaneous development of resistant barrier films through CVD experiments, alongside gas phase analysis, simulation and numerical computation. The experimental information obtained through this approach is utilized in order to enrich previous literature models or define completely novel deposition mechanisms. Through 3D representation of the reactor spatial domain, the developed chemical models are implemented in order to replicate the deposition process via simulation. Computational fluid dynamics (CFD) calculations are used to understand the particularities of film formation in confined spaces and complex 3D-parts, obtain predictions in terms of gas phase and solid phase composition, as well as investigate potentials and solutions for optimization of the deposition process. The established correlations between process conditions, films structure, composition and properties, alongside the integration of a coupled computational and experimental approach, are used to arrive at durable silica-based materials with sustainable barrier performance, flexible for utilization in diverse application domains

Large temperature range model for theatmospheric pressure chemical vapor deposition ofsilicon dioxide films on thermosensitive substrates

tCoating complex surfaces by functional amorphous silica films for new applications includ-ing energy harvesting and health depends on the operating range and robustness of theirdeposition process. In this paper, we propose a new kinetic model for the atmosphericpressure chemical vapor deposition of SiO2films from TEOS/O2/O3valid in the 150−520◦C temperature range, thus allowing for treating thermally sensitive substrates. For this,we revisit reported chemical schemes in Computational Fluid Dynamics simulations con-sidering original experimental data on the deposition rate of SiO2films from a hot-wallreactor. The new model takes into account for the first time a thermal dependency of thedirect formation of SiO2from TEOS and O3and yields excellent agreement in both shapeand value between experimental and calculated local deposition rate profiles. The modelprovides non-measurable information such as local distributions of species concentrationand reaction rates, which are valuable for developing optimized CVD reactor designs. Origi-nal solutions for the introduction of the reactants are proposed, to uniformly coat complexand/or large parts at a wide temperature range

An innovative GC-MS, NMR and ESR combined, gas-phase investigation during chemical vapor deposition of silicon oxynitrides films from tris(dimethylsilyl)amine

Tris(dimethylsilyl)amine (TDMSA) is used in the presence of O2 and NH3 for the atmospheric pressure chemical vapor deposition (CVD) of conformal, corrosion barrier silicon oxynitride (SiOxNy) films at moderate temperature. Plausible decomposition pathways taking place during the process, as well as resulting gas-phase by-products, are investigated by an innovative methodology, coupling solid-state films characteristics with gas phase analysis. Liquid NMR, gas chromatography coupled with mass spectrometry (GC-MS) and electron spin resonance (ESR) allow probing stable compounds and radical intermediate species in the gas phase. At least fifteen by-products are identified, including silanols, siloxanes, disilazanes, silanamines, and mixed siloxane–silanamine molecules, in addition to more usual compounds such as water. The radical dimethylsilane, Me2HSi˙, is noted across all experiments, hinting at the decomposition of the TDMSA precursor. Deposition of SiOxNy films occurs even in the absence of NH3, demonstrating the judicious choice of the silanamine TDMSA as a dual source of nitrogen and silicon. Additionally, the presence of Si–H bonds in the precursor structure allows formation of SiOxNy films at temperatures lower than those required by other conventional silazane/silanamine precursors. Addition of NH3 in the inlet gas supply results in lower carbon impurities in the films. The identified by-products and formulated decomposition and gas-phase reactions provide stimulating insight and understanding of the deposition mechanism of SiOxNy films by CVD, offering possibilities for the investigation of representative chemical models and process simulation

Tunable SiO2 to SiOxCyH films by ozone assisted chemical vapor deposition from tetraethylorthosilicate and hexamethyldisilazane mixtures

Silica and silica-based materials with tunable functionalities are frequently encountered in low-k material applications, porous membranes, and microelectonic devices. In the present study, an innovative O2/O3 assisted CVD process for the deposition of such films at moderate temperature is presented, based on a dual precursor chemistry from hexamethyldisilazane (HMDS) and tetraethyl orthosilicate (TEOS). Films with tunable carbon content were obtained through variation of the HMDS flow ratio. A comprehensive FT-IR study reveals the transition of the material from a SiOxCyH type film containing -CH3 moieties, to a methyl-free SiOx film with the increase of the temperature. At the same time the water contact angle of 81.0° at 400°C is decreased to 52.8° at 550°C, related to the absence of methyl moieties in the latter. Ion beam analysis (IBA) confirms the lack of carbon in the films when deposition temperatures are equal to or exceed 500°C. The resistance to liquid corrosion is investigated as a function of the deposition temperature; SiOx type films present a low Pliskin etching rate of 15 Å.s-1, with this value increasing to 60 Å.s-1 for the SiOxCy:CH3 films produced at the lower temperatures. It is found that the addition of HMDS to a TEOS chemistry can be utilized to modulate the film composition from SiOx to SiOxCyH and by such, tune the film functional properties, in particular its etching rate, opening the way to the development of new sacrificial films

Network hydration, ordering and composition interplay of chemical vapor deposited amorphous silica films from tetraethyl orthosilicate

The chemical or mechanical performance of amorphous SiO2 films depend on intrinsic physicochemical properties, which are intimately linked to atomic and molecular arrangements in the Si–O–Si network. In this context, the present work focuses on a comprehensive description of SiO2 films deposited from a well-established chemical vapor deposition process involving tetraethyl-orthosilicate, oxygen and ozone, and operating at atmospheric pressure in the range 400–550 °C. The connectivity of the silica network is improved with increasing the deposition temperature (Td) and this is attributed to the decreased content of hydrated species through dehydration-condensation mechanisms. In the same way, the critical load of delamination increases with increasing Td thanks to the silicon substrate oxidation. The utilization of a O2/O3 oxidizing atmosphere involving the oxidation of intermediates species by O2, O3 and O., allows increasing the deposition rate at moderate temperatures, while minimizing carbon, H2O and silanol contents to extremely low values (4.5 at.% of H). The SiOx stoichiometry and Td interplay reveals two distinct behaviors before and above 450 °C. The best corrosion resistance of these films to standard P-etching test is obtained for the minimum silanol content and the best network molecular ordering, with an etching rate of 4.0 ± 0.1 Å/s at pH = 1.5. The elastic modulus and hardness of the films remain stable in the investigated range of deposition temperature, at 64.2 ± 1.7 and 7.4 ± 0.3 GPa respectively, thanks to the low content in silanol groups

Etude experimentale et modélisation cinétique du procédé de dépot chimique en phase vapeur de couches minces SiOxCy pour des barrières de corrosion aqueuses

Le dépôt de matériaux à base de silice est largement utilisé dans de nombreux secteurs industriels, dont la microélectronique, l'emballage alimentaire, la séparation des gaz et la pharmacie. Selon l'application cible, ces matériaux doivent répondre à des besoins spécifiques en termes de propriétés mécaniques, durabilité et composition. La mise en œuvre de tels revêtements dans des applications pharmaceutiques nécessite, plus précisément, de bonnes propriétés de barrière aqueuse et anti-diffusion, ainsi qu'une résistance efficace à la corrosion. La résistance hydrolytique et la durabilité des revêtements sont directement liées au niveau de densification du réseau céramique. Dans le cas de SiO2 amorphe, une réticulation et densification de réseau améliorée peut être induite par le remplacement partiel des anions O2- par des anions N3- (ou C4-), produisant des revêtements d'oxynitrure (SiOxNy) ou de l'oxycarbure (SiOxCy) de silicium plus dense qui peuvent répondre aux exigences de performances dictées par les différentes applications pharmaceutiques. Cependant, très peu d'informations sont disponibles dans la littérature concernant le dépôt de revêtements SiOxNy en fonction des contraintes spécifiques à l'application: à savoir la réalisation de films chimiquement inertes sur des substrats 3D complexes, déposés à pression atmosphérique et à température modérée (< 570 ° C), avec des taux de dépôt élevés. Pour atteindre les objectifs ci-dessus, le dépôt de films à base de silice amorphe est entrepris via l'utilisation d'un procédé CVD thermique défini autour de nouvelles chimies réactives. Les voies chimiques réactives aident à la production de SiOxNy à des températures inférieures aux températures conventionnelles et, plus important, compatibles avec les substrats thermosensibles. L'augmentation progressive des teneurs en N et C dans les dépôts est réalisée grâce à des molécules précurseurs et des compositions de gaz réactifs soigneusement sélectionnées. Des voies de dépôt innovantes, basées sur des combinaisons de précurseurs classiques contenant du silicium tels que le tétraéthylorthosilicate (TEOS) ou l'hexaméthyldisilazane (HMDS), et d'autres composés nouveaux tels que la tris(diméthylsilyl)amine (TDMSA) sont explorées. L'incorporation progressive d'azote et de carbone dans les films étant au coeur de ce travail, l'évolution qui en résulte du réseau silicaté est largement étudiée à travers des protocoles de caractérisation physico-chimique, structurale et mécanique. Une approche multidisciplinaire est adoptée, combinant la science des matériaux, la chimie analytique et l'ingénierie des procédés d'une manière qui implique le développement simultané de films barrières résistants grâce à des expériences CVD, parallèlement à l'analyse en phase gazeuse, à la simulation et au calcul numérique. Les informations expérimentales obtenues grâce à cette approche sont utilisées pour enrichir les modèles de la littérature ou définir des mécanismes de dépôt complètement nouveaux. Grâce à une représentation 3D du domaine spatial du réacteur, les modèles chimiques développés sont mis en oeuvre afin de reproduire le processus de dépôt par simulation. Les calculs de mécanique des fluides numérique (MFN) sont utilisés pour comprendre les particularités de la formation du dépôt dans les espaces confinés et les pièces 3D complexes, obtenir des prédictions en termes de composition en phase gazeuse et solide, ainsi que pour étudier les potentiels et les solutions pour l'optimisation du processus de dépôt. Les corrélations établies entre les conditions de processus, la structure des films, la composition et les propriétés, ainsi que l'intégration d'une approche informatique et expérimentale couplée, sont utilisées pour arriver à des matériaux durables à base de silice avec des performances de barrière efficaces, flexibles pour une utilisation dans divers domaines d'application.The deposition of silica-based materials is widely used in numerous industrial sectors, including microelectronics, food packaging, gas separation and pharmaceutics. Depending on the targetapplication, these materials are required to fulfil specific requirements in terms of mechanical properties, durability, and composition. The implementation of such coatings in pharmaceutics applications require, more specifically, good aqueous barrier and anti-diffusion properties, as well as effective corrosion resistance. The hydrolytic resistance and the durability of the coatings is directly linked to the level of densification of the ceramic network. In the case of amorphous SiO2, an improved network cross-linking, and by consequence densification, can be induced through the partial replacement of the O2- anions by N3- (or C4-) ones, producing denser amorphous silicon oxynitride (SiOxNy) or silicon oxycarbide (SiOxCy) coatings that can meet the performance requirements dictated by the various pharmaceutical applications. However, very little information is available in the literature concerning the deposition of SiOxNy coatings in accordance to the application-specific constraints: namely the production of chemically inert films on complex, 3D substrates, deposited at atmospheric pressure and at moderate temperatures (<570°C), with high deposition rates. To achieve the above goals, the deposition of amorphous silica-based films is undertaken via the utilization of a thermal CVD process defined around reactive, novel chemistries. The reactive chemical pathways aids in the production of SiOxNy at temperatures lower than the conventional ones, and more importantly, compatible with thermosensitive substrates. The gradual increase in N and C contents in the deposits is carried out through carefully selected precursor molecules and reagent gas compositions. Innovative deposition routes, based on single or dual-precursor combinations of classic silicon-containing precursors such as tetraethylorthosilicate (TEOS) or hexamethyldisilazane (HMDS), and more novel compounds such as tris(dimethylsilyl)amine (TDMSA) are explored. Since the progressive incorporation of nitrogen and carbon in the films is at the core of this work, the resulting evolution of the silicate network is extensively studied through physicochemical, structural and mechanical characterization protocols. A multidisciplinary approach is embraced, combining materials science, analytical chemistry and process engineering in a way that involves the simultaneous development of resistant barrier films through CVD experiments, alongside gas phase analysis, simulation and numerical computation. The experimental information obtained through this approach is utilized in order to enrich previous literature models or define completely novel deposition mechanisms. Through 3D representation of the reactor spatial domain, the developed chemical models are implemented in order to replicate the deposition process via simulation. Computational fluid dynamics (CFD) calculations are used to understand the particularities of film formation in confined spaces and complex 3D-parts, obtain predictions in terms of gas phase and solid phase composition, as well as investigate potentials and solutions for optimization of the deposition process. The established correlations between process conditions, films structure, composition and properties, alongside the integration of a coupled computational and experimental approach, are used to arrive at durable silica-based materials with sustainable barrier performance, flexible for utilization in diverse application domains

Beyond surface nanoindentation: Combining static and dynamic nanoindentation to assess intrinsic mechanical properties of chemical vapor deposition amorphous silicon oxide (SiOx) and silicon oxycarbide (SiOxCy) thin films

International audienceNanoindentation is a well-known technique to assess the mechanical properties of bulk materials and films. Despite that, nanoindentation of thin films is not straightforward, given that the measured properties are composite information from a film/substrate system and depend on the indentation depth. By using dynamic indentation experiments and analytical or empirical models, we assessed the intrinsic film properties of chemical vapor deposited silicon oxide (SiO x) and silicon oxycarbide (SiO x C y) thin films with thicknesses ranging from 60 to 700 nm. In this work, the Bec rheological model and several mixing laws were reviewed. Measured Young modulus appeared to be affected by the substrate properties more than hardness: for the thinnest films, moduli were measured at ca. 90 GPa whereas intrinsic moduli were calculated at ca. 50 GPa. Using calculated intrinsic film modulus and hardness, it was possible to establish correlations between these properties, the chemical composition and the structural organization of the films

Silicon Oxynitride Coatings Are Very Promising for Inert and Durable Pharmaceutical Glass Vials

Glass packaging of novel medicinal molecules is challenged by hydrolysis of the glass network from an interaction with the stored drug, likely to result in leaching of constituent elements of the glass into the solution. We have succeeded in applying chemical-vapor-deposited silicon oxynitride coatings from a highly reactive trisilylamine derivative molecule as a precursor, at a temperature below 580 °C, opening up the possibility utilizing such coatings on glass surfaces. We demonstrate that such silicon oxynitride coatings applied on the internal surface of pharmaceutical vials prevent degradation, providing chemical inertness and withstanding severe screening conditions of the United States Pharmacopeia USP chapter. Fine structural determination and atomistic modeling of the Si–O–N network of the films confirm the nitrogen substitution of oxygen and densification of the silicate network through the addition of the former. The achieved barrier properties and excellent performance of these coatings pave the way toward sustainable packaging with improved product shelf life, transferable to multiple applications of surface coatings