Toward the Improvement of the Microstructure of Chemical Vapor Deposited Aluminum on Silicon Carbide

Abstract

This paper presents results on the chemical vapor deposition of aluminum on silicon carbide starting from triisobutylaluminum. The deposited films show important systematic trends in surface roughness and porosity. Considering literature information on the deposition of aluminum on silicon, pretreatments of the deposition surface with hydrofluoric acid and/or titanium tetrachloride have been tested. They lead to films with a smoother morphology and stronger adhesion with the substrate than in the case of an untreated surface. Different heteroelements are observed at the interface under these conditions. A short thermal activation of the nucleation process following these pretreatments does not unambiguously improve the characteristics of the aluminum films. The obtained results can be considered for the modification of surface characteristics of silicon carbide particles which are used in discontinuously reinforcement aluminum composite materials with the aim to improve their mechanical properties and corrosion resistance as well as their fabrication process.The fabrication and operating conditions of a composite material depend strongly on the physicochemical characteristics of the matrix and on the near-surface region of the reinforcement. When these two parts are joined, an interphase is often created, whose role is critical in the mechanical behavior of the material. Processing of high performance interphases is a complex task, and the ultimate verification of its accomplishment requires ͑i͒ the fabrication of the composite material leading to the identification of the phases formed, and ͑ii͒ the subsequent performing of appropriate mechanical tests to allow final validation of the selection made a priori for the prerequisite application. Optimization of a composite material often comes through a process of trial and error which may be long, expensive, and difficult to establish. It is thus important to minimize and simplify it whenever possible. This can be achieved in part by various experimental simulations of the interfacial zone, leading to the fabrication of diffusion couples, to the identification of interfacial phases, and to the characterization of their physicochemical and mechanical properties. Examples of these approaches, concerning the ͑silicon-carbon͒/titanium and the silicon/metal systems can be found in Ref. 1-4 and in Ref. 5-8, respectively. However, they are exclusively focused on the physicochemical characterization of the interphases involved.For many years we have used the chemical vapor deposition ͑CVD͒ technique for the investigation of interfaces which reproduce those existing in metal matrix composites ͑MMCs͒. We thus studied the ͑Si-C͒/Ti model system 9 and the ͑Si-C͒/͑Ti-22Al-23Nb͒ system of technological interest, 10 with particular emphasis on the composition and morphology of the microstructures obtained. In the present work we investigate, for the first time to our knowledge using CVD, the aluminum/silicon carbide ͑Al/SiC͒ couple. This system is involved in power electronics ap...

Conformity of Aluminum Thin Films Deposited onto Micro‐Patterned Silicon Wafers by Pulsed Laser Deposition, Magnetron Sputtering, and CVD

“…This is in agreement with the high value of Rz of this sample. This morphology was also observed for Al films deposited on polished bulk Al substrates and on SiC15 and is characteristic of the previously mentioned trends concerning the competition between nucleation and growth of CVD‐processed Al films.…”

“…A major concern of MOCVD‐processed Al films is the often rough microstructure obtained due to the reluctance of Al to nucleate on silicon and silicon‐based ceramic surfaces. This behavior has been extensively reported in the literature and has been faced, at least partially, through appropriate treatments of the involved surfaces (see the literature15 and references therein). The nature of the Al precursor also influences the resulting film morphology.…”

Microstructure of Metallorganic Chemical Vapor Deposited Aluminum Coatings on Ti6242 Titanium Alloy

“…Figure 2 presents the Arrhenius plot of DMEAA deposition on bare Ti6242 at 1330 Pa. From this diagram, activation energy of 0.3 eV was measured. The DMEAA processed coating, AlD1, exhibits an average roughness of 0.5 m and a continuous base similar with results found by Vahlas et al 11 Neither preferential orientation nor carbon contamination could be observed in AlD1.…”

“…Vahlas et al 11 reported that MOCVD processed Al coatings from TIBA on silicon carbide strongly depend on surface pretreatments. Deposition on Ti6242 is more straightforward as nucleation is easier on metallic surfaces.…”

Multiscale modeling and experimental analysis of chemical vapor deposited aluminum films: Linking reactor operating conditions with roughness evolution

“…Various methods are developed for the production of Al and Al-containing thin films, among which chemical vapor deposition (CVD) combines high growth rates and conformal coverage of complex surfaces (Thomann et al, 2011). However CVD processed Al films suffer from a rough microstructure, despite efforts made to attenuate it (Vahlas et al, 2001).…”