Aspects of nitrogen surface chemistry relevant to TiN chemical vapor deposition

NH{sub 3} is an important component of many chemical vapor deposition (CVD) processes for TiN films, which are used for diffusion barriers and other applications in microelectronic circuits. In this study, the interaction of NH{sub 3} with TiN surfaces is examined with temperature programmed desorption (TPD) and Auger electron spectroscopy. NH{sub 3} has two adsorption states on TiN: a chemisorbed state and a multilayer state. A new method for analyzing TPD spectra in systems with slow pumping speeds yields activation energies for desorption for the two states of 24 kcal/mol and 7.3 kcal/mol, respectively. The sticking probability into the chemisorption state is {approximately}0.06. These results are discussed in the context of TiN CVD. In addition, the high temperature stability of TiN is investigated. TiN decomposes to its elements only after heating to 1300 K, showing that decomposition is unlikely to occur under CVD conditions

Development of a process simulation capability for the formation of titanium nitride diffusion barriers

Titanium nitride (TiN) films deposited by chemical vapor deposition (CVD) techniques are of interest for a wide range of commercial applications. In this report, the authors describe a mechanism that predicts Tin film growth rates from TiCl{sub 4}/NH{sub 3} mixtures as a function of process parameters, including inlet reactant concentrations, substrate temperatures, reactor pressures, and total gas flow rates. Model predictions were verified by comparison with the results of TiN deposition experiments in the literature and with measurements made in a new stagnation-flow reactor developed for the purpose of testing deposition mechanisms such as this. In addition, they describe ab initio calculations that predict thermodynamic properties for titanium-containing compounds. The results of calculations using Moeller-Plesset perturbation theory, density functional theory, and coupled cluster theory are encouraging and suggest that these methods can be used to estimate thermodynamic data that are essential for the development of CVD models involving transition-metal compounds. Finally, measurements of the adsorption and desorption kinetics of NH{sub 3} on TiN films using temperature-programmed desorption are described and their relevance to TiN CVD and mechanism development are discussed

The reaction of NH{sub 3} with TiN: Implications for CVD

Since NH{sub 3} is an important component of TiN chemical vapor deposition processes, understanding the NH{sub 3}/TiN surface interaction is crucial to developing a model for the overall reaction. Temperature programmed desorption experiments show that NH{sub 3} adsorbs molecularly on amorphous TiN surfaces. Chemisorption occurs at only {approximately}5% of the surface sites, with an activation energy for desorption of 24 kcavmol. The sticking probability into this state is 0.06 at 100 K. In addition, NH{sub 3} adsorbs with high probability into a multilayer state with an activation energy for desorption of 7.3 kcal/mol, similar to that found in other systems. NH{sub 3} does not dissociate on TiN. Under CVD conditions, however, the reactivity of NH{sub 3} on TiN may increase and surface reactions may play a part in film growth

Gas-phase chemistry during the conversion of cyclohexane to carbon: Flow reactor studies at low and intermediate pressure

The gas-phase branching during the conversion of cyclohexane to solid carbon has been measured in a high-temperature-flow reactor. The experiments show that cyclohexane decomposes into a broad distribution of hydrocarbons that further decompose into the more kinetically stable products hydrogen, methane, acetylene, ethylene, benzene, and PAH. At 1363 K, the evolution to these species occurs quickly. We also observe the buildup of significant amounts of aromatic molecules at later stages in the decomposition, with as much as 15% of the total carbon in PAH and 25% in benzene. At later stages, the gas-phase molecules react slowly, even though the system is not at equilibrium, because of their kinetic stability and the smaller radical pool. The decomposition does not appear to depend sensitively on pressure in the regime of 25 to 250 torr. Thus, to a first approximation, these results can be extrapolated to atmospheric pressure

Heats of formation and bond energies in group III compounds

We present heats of formation and bond energies for Group-III compounds obtained from calculations of molecular ground-state electronic energies. Data for compounds of the form MX0 are presented, where M = B, Al, Ga, and In, X = H, Cl, and CH3, and n = 1-3. Energies for the B, Al, and Ga compounds are obtained from G2 predictions, while those for the In compounds are obtained from CCSD(T)/CBS calculations ; these are the most accurate calculations for indium-containing compounds published to date. In most cases, the calculated thermochemistry is in good agreement with published values derived from experiments for those species that have well-established heats of formation. Bond energies obtained from the heats of formation follow the expected trend (Cl >> CH3 - H). However, the CH3M-(CH3)2 bond energies obtained for trimethylgallium and trimethylindium are considerably stronger (> 15 kcal mol-1) than currently accepted values

Chemical vapor deposition of tin oxide: fundamentals and applications

Tin oxide thin layers have very beneficial properties such as a high transparency for visible light and electrical conductivity making these coatings suitable for a wide variety of applications, such as solar cells, and low-emissivity coatings for architectural glass windows. Each application requires different properties of the tin oxide layer. These properties can be tuned by adjusting the parameters of the chemical vapor deposition (CVD) process, the main technique used for applying the tin oxide layer to the substrate. This paper discusses the state of the art of the kinetic models for tin oxide CVD. In the case of organometallic precursors the gas-phase chemistry may be initiated by cleavage of the tin-carbon bond, followed by radical-driven chain reactions that enhance the overall decomposition rate. However, in commercial tin oxide CVD reactors the gas-phase temperature may be too low or the residence time too short for these reactions to occur, thereby favoring surface chemistry. Preliminary investigations of the MBTC-H2O-O 2 chemistry indicate that a mechanism comprising the reaction between gaseous oxygen and an adsorbed MBTC-H2O complex is a plausible model

Mechanical Properties in Metal-Organic Frameworks: Emerging Opportunities and Challenges for Device Functionality and Technological Applications

Some of the most remarkable recent developments in metal-organic framework (MOF) performance properties can only be rationalized by the mechanical properties endowed by their hybrid inorganic-organic nanoporous structures. While these characteristics create intriguing application prospects, the same attributes also present challenges that will need to be overcome to enable the integration of MOFs with technologies where these promising traits can be exploited. In this review, emerging opportunities and challenges are identified for MOF-enabled device functionality and technological applications that arise from their fascinating mechanical properties. This is discussed not only in the context of their more well-studied gas storage and separation applications, but also for instances where MOFs serve as components of functional nanodevices. Recent advances in understanding MOF mechanical structure-property relationships due to attributes such as defects and interpenetration are highlighted, and open questions related to state-of-the-art computational approaches for quantifying their mechanical properties are critically discussed

Contribution to the modeling of CVD silicon carbide growth

The modeling of the growth of silicon carbide from the vapor phase in the Si-C-H system requires a good understanding of the gas-phase chemistry. The object of this paper is to complement the previous studies on the kinetic modeling of the gas-phase in the system SiH4 / C3H8. To date, kinetic approaches to modeling the gas-phase chemistry have not been fully developed Previous kinetic models have only dealt with the pyrolysis of individual precursors (silane and propane) without allowing for the formation of organosilicon species. This study provides a progress report on our efforts to develop a full gas-phase mechanism that includes organosilicon compounds. Rate constants for this mechanism are determined where possible from experimental data available in the literature. However, for several important reactions, experimental data are not available. Consequently, we are performing ab initio calculations to determine activation energies and are using RRKM calculations to estimate pressure fall-off effects for unimolecular reactions. In this contribution, we focus on the formation of methylsilane H3SiCH3 and discuss the importance of such species in the gas-phase chemistry of SiC deposition

Plasma enhanced MOCVD of smooth nanometer-sized Metal/Silicon Single- and multilayer films

Hamelmann F, Haindl G, Aschentrup A, et al. Plasma enhanced MOCVD of smooth nanometer-sized Metal/Silicon Single- and multilayer films. In: Allendorf MD, Besman TM, eds. Chemical Vapor Deposition CVD XV, ECS Proc. PV. 2000: 131