A comprehensive insight in the MOCVD of aluminum through interaction between reactive transport modeling and targeted growth experiments

Growth experiments and reactive transport modeling were combined to formulate a comprehensive predictive model for aluminum growth from dimethylethylamine alane. The growth-rate profile was experimentally investigated as a function of substrate temperature. The reactive transport model, built under the computational fluid dynamics software PHOENICS, was used to reproduce the experimental measurements and to contribute to the understanding of the aluminum growth process, under sub-atmospheric pressure conditions. The growth mechanism of aluminum films was based on well established in literature reaction order and activation energy of homogeneous and heterogeneous chemical reactions. The reactive transport model was used further to investigate the effect of some key operating parameters on the process output. Simulation results are suggestive of modifications in the operating parameters that could enhance the growth rate and the spatial uniformity of the film thickness

Shape optimization of a showerhead system for the control of growth uniformity in a MOCVD reactor using CFD-based evolutionary algorithms

A steady state, laminar flow coupled with heat transfer, gas-phase and surface chemistry, is numerically solved for the optimal design of a showerhead gas delivery system in an axis-symmetrical MOCVD reactor. The design method involves an evolutionary algorithm based on CFD simulations. A finite-volume CFD code for aluminum growth provides the numerical predictions of the growth rate and its spatial variation over the substrate. A multilevel evolutionary algorithm is used to continuously adjust the shape of the shower plate so as to minimize the spatial variation of the growth rate. A 5-variable parameterization of the shower plate is investigated and a near-optimal solution is proposed and compared to the original configuration of the shower plate

Reaction and Transport Interplay in Al MOCVD Investigated Through Experiments and Computational Fluid Dynamic Analysis

An improved reactive transport model of a metallorganic chemical vapor deposition process for the growth of aluminum films from dimethylethylamine alane is developed. The computational fluid dynamics model is built under PHOENICS software for the simulation of the coupled fluid flow, heat transfer, and chemistry. The growth mechanism of aluminum films is based on wellestablished, in the literature, reaction order and activation energy of gas-phase and surface reactions. The improvement of the model against a simplified model is established. The interplay of reaction and transport is elucidated. In particular, the important effects of the gas-phase reaction and of the showerhead system are revealed; accounting for gas-phase along with surface reactions for the flow details in the showerhead and for the three-dimensional geometry induced by the distribution of the holes in the showerhead yields substantial enhancement of the predictive capability of the model. The satisfactory agreement between model predictions and growth-rate measurements allows one to understand and improve the process. The model is further used to investigate the effect of key operating parameters on the characteristics of the aluminum films. Simulation results are suggestive of modifications in the operating parameters that could enhance the growth rate and its spatial uniformity

Etude de l’adsorption et de la tension interfaciale solide-liquide de systèmes ternaires à base de zinc

A l’aide de la méthode des angles dièdres nous avons déterminé les isothermes de tension d’interface du zinc solide en équilibre avec les alliages liquides Bi, Cd, et Pb, Sn. A partir de ces résultats expérimentaux et de l’équation d’adsorption de Gibbs nous avons calculé les coefficients d’enrichissement interfacial en Cd et en Sn. L’étain s’adsorbe fortement à l’interface entre Zn solide et Pb liquide et conduit à une diminution importante de la tension interfaciale de ce système. Par contre, le cadmium n’est pas tensioactif à l’interface entre Zn solide et Bi liquide et les faibles variations de la tension interfaciale en fonction de la composition observées dans le ternaire ZnBiCd sont essentiellement dues à des effets de volume. Ces résultats sont en accord qualitatif avec un modèle thermodynamique simple qui permet d’estimer l’énergie libre d’adsorption à dilution infinie d’un soluté C à l’interface entre un solide A et un liquide B

Chemical vapor deposition of pyrolytic carbon on polished substrates

Pyrolytic carbon thin (4-100 nm) films were obtained from méthane in a hot wall reactor on optically polished inert substrates by varying the déposition time and temperature. They were characterized by all modes of TEM. They are composed in majority of lamellar pyrocarbon whose thickness and disorder increases with increasing temperature. Isotropic carbon islands are also observed at the upper surface of the film

Growth mechanisms of MOCVD processed Ni thin films

The main gaseous by-products during the processing of nickel films by MOCVD from nickelocene have been analyzed by on-line mass spectrometry. The evolution of relative concentration of CH4, C5H6, and C5H10 with time, pressure, temperature, and hydrogen flow has been quantified and related with the characteristics, mainly carbon content, of the Ni films. The obtained results allowed to investigate the dissociation of nickelocene leading to the growth of Ni films. Two possibilities are proposed to prevail : Either the metal-ligand bond is dissociated, and the ligand is hydrogenated and desorbed, or the ligand itself is decomposed on the surface leading to the incorporation of carbon in the deposits. The process is controled by a Langmuir-Hinshelwood mechanism based on a competitive coverage of the surface by nickelocene or hydrogen atoms

Chemical Vapour Deposition processes of metallic amorphous or nanocrystalline thin films

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