Mass spectrometry as a tool study CVD process

Mass spectrometry as a tool study CVD process. Application of two mass spectrometric (MS) techniques to study chemical vapour deposition from organometallic precursors is described. CpCuPEt3 (Cp = η5-C5H5, Et =C2H5) was used as a model precursor in this work

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

CVD of pure copper films from amidinate precursor

Copper(I) amidinate [Cu(i-Pr-Me-AMD)]2 was investigated to produce copper films in conventional low pressure chemical vapor deposition (CVD) using hydrogen as reducing gas-reagent. Copper films were deposited on steel, silicon, and SiO2/Si substrates in the temperature range 200–350°C at a total pressure of 1333 Pa. The growth rate on steel follows the surface reaction between atomic hydrogen and the entire precursor molecule up to 240°C. A significant increase of the growth rate at temperatures higher than 300°C was attributed to thermal decomposition of the precursor molecule. It is shown that [Cu(i-Pr-Me-AMD)]2 meets the specifications for the metal organic chemical vapor deposition of Cu-based alloy coatings containing oxophilic elements such as aluminum

Surface-driven, one-step chemical vapor deposition of γ-Al4Cu9 complex metallic alloy film

The present paper is a paradigm for the one-step formation of complex intermetallic coatings by chemical vapor deposition. It genuinely addresses the challenge of depositing an intermetallic coating with comparable contents of Cu and Al. Depending on processing conditions, a pure γ-Al4Cu9 and multi-phase Al-Cu films are grown with wetting properties of the former being similar to its bulk counterpart. The deposition process and its parametric investigation are detailed. Two metalorganic precursors are used taking into account their transport and chemical properties, and deposition temperature ranges. On line and ex situ characterizations enlighten the competition which occurs at the growing surface between molecular fragments, and which limits growth rates. Notably, introducing a partial pressure of hydrogen gas during deposition reduces Al growth rate from dimethylethylamine alane (DMEAA), by displacing the hydrogen desorption equilibrium. This Al partial growth rate decrease is not sufficient to achieve a Cu/Al atomic ratio that is high enough for the formation of intermetallics with close Al and Cu compositions. A fivefold increase of the flux of the gaseous copper(I) cyclopentadienyl triethylphosphine CpCuPEt3, whereas the DMEAA flux remains constant, results in the targeted Al/Cu atomic ratio equal to 44/56. Nevertheless, the global growth rate is rendered extremely low by the deposition inhibition caused by a massive phosphine adsorption (-PEt3). Despite these limitations, the results pave the way towards the conformal coating of complex surface geometries by such intermetallic compounds

Thermal behaviour of CpCuPEt3 in gas phase and Cu thin films processing

Decomposition of CpCuPEt3 (Cp=NNN(η5-C5H5)) and MOCVD of Cu films from CpCuPEt3 have been investigated in the frame of an ongoing project on the processing of Cu-containing coatings. The behaviour of CpCuPEt3 vapours under heating conditions was studied by in situ mass spectrometry. It was established that this compound is monomeric in gas phase. Its decomposition mechanism on hot surface was proposed. From mass spectroscopy experiments, it was established that decomposition in vacuum begins at 150 °C with evolution of PEt3. Beyond 270 °C, formation of cyclopentadiene is observed, indicating that a change in decomposition mechanism occurs. The saturating vapour pressure of CpCuPEt3 was estimated through static method, in order to optimize transport conditions and to control the molar fraction of the precursor in the gas phase. Finally, growth rate and microstructure of MOCVD processed Cu films from CpCuPEt3 have been investigated

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

Chemical vapor deposition of iron, iron carbides, and iron nitride films from amidinate precursors

Iron bis(N,N-diisopropylacetamidinate) [Fe2(µ-iPr-MeAMD)2(2-iPr-MeAMD)2] and iron bis(N,N-di-tert-butylacetamidinate) [Fe(tBu-MeAMD)2] were used as precursors for the metallorganic chemical vapor deposition (MOCVD) of iron-containing compounds including pure iron, iron carbides, Fe3C and Fe4C, and iron nitrides Fe4C. Their decomposition mechanism involves hydrogen migration followed by dissociation of the Fe–N bond and the release of free hydrogenated ligand (HL) and radicals. Surface intermediates are either released or decomposed on the surface providing Fe–N or Fe–C bonds. MOCVD experiments were run at 10 Torr, in the temperature ranges of 350–450°C with Fe2(µ−iPr-MeAMD)2(2-iPr-MeAMD)2 and 280–350°C with Fe(tBu-MeAMD)2. Films prepared from Fe2(µ−iPr-MeAMD)2(2-iPr-MeAMD)2 contain Fe, Fe3C, and Fe4C. Those prepared from Fe(tBu-MeAMD)2 contain Fe, Fe3C, and also Fe4C or Fe4N, depending on the temperature and hydrogen to precursor ratio (H/P) in the input gas. The room-temperature coercive field of films processed from Fe(tBu-MeAMD)2 is 3 times higher than that of the high temperature processed Fe4N films

Decomposition Schemes of Copper(I)N1′-Diisopropylacetamidinate During Chemical Vapor Deposition of Copper

Copper(I) N1N′-diisopropylacetamidinate [Cu(amd)]2 (amd = CH(CH352NC(CH35NCH(CH3525, an oxygen and halogen-free compound, was previously tested as precursor for pure copper CVD and ALD films. The present work deals with the investigation of the composition and of the reactivity of the gas phase during the CVD process. The work was performed by mass spectrometry as a function of temperature in two different, though complementary environments: (A) in a miniature, low pressure hot wall CVD reactor, (B) in a cold wall reactor operating at subatmospheric pressure. (A) revealed that the onset of thermal decomposition is 140°C and 130°C in vacuum and in the presence of hydrogen, respectively; maximal decomposition degree is reached at temperature higher than 200°C. The protonated ligand H(amd) is the main gaseous decomposition by-product; propene CH2 CHCH3, acetonitryle CH3C≡N and iminopropane CH3C(CH35 NH are also observed in vacuum. Heterogeneous decomposition mechanism both in vacuum and hydrogen presence is discussed

Iron amidinates as precursors for the MOCVD of iron-containing thin films

Iron amidinates as precursors for the MOCVD of iron-containing thin film