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Title:Chemical kinetic studies of titanium silicide chemical vapor deposition
Author(s):Mendicino, Michael Anthony
Doctoral Committee Chair(s):Seebauer, Edmund G.
Department / Program:Chemical and Biomolecular Engineering
Discipline:Chemical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Engineering, Chemical
Abstract:A methodology has been developed to study CVD systems which combines real-time analysis during growth with surface analysis in UHV. This methodology was applied to TiSi$\sb2$ CVD. A predictive kinetic model was formulated that describes growth, and it showed good agreement with experimental results. The model predictions, growth results, and UHV studies were used to solve all critical processing problems in TiSi$\sb2$ CVD.
Four regimes of TiSi$\sb2$ growth were identified: (1) film nucleation and coalescence, (2) initial growth transient, (3) steady-growth where heterogeneous reaction from SiH$\sb4$ controls Si consumption, and (4) final growth transient where Si diffusion controls consumption.
Film nucleation was found to be enhanced by the presence of defects on the substrate surface. Oxygen contamination inhibited nucleation. Selective nucleation enhancement was accomplished by growing Si nuclei from SiH$\sb4$ to generate defects and remove native oxide. Since this process is only semi-selective, these nuclei are converted to TiSi$\sb2$ at the start of growth and then selectively etched by Cl$\sb2$ leaving only defects on the Si surface.
Regime #2 was characterized by a growth rate maximum and then a decrease to roughly 60% of its highest value. Intentionally halting growth during this transient showed the material was C49 TiSi$\sb2$. As the film thickened, a phase transformation to C54 TiSi$\sb2$ occurred. Si consumption was small and constant during growth of the C49 phase then increased with the C54 transition.
Regime #3 was characterized by steady-growth where heterogeneous reaction from SiH$\sb4$ successfully competed with Si diffusion, even for thin films. Si consumption decreased in this regime with decreasing temperature and was characterized by an activation energy of 6 $\pm$ 2 kcal/mol. Reducing the P$\sb{\rm TiCl4}$ in this regime was also found to decrease Si consumption.
The duration of regime #3, and thus the start of the final transient regime #4, was determined by a critical thickness at which Si diffusion can no longer supply enough Si to complete the TiSi$\sb2$ stoichiometry. At this point SiH$\sb4$ adsorption is enhanced due to changes in the reacting surface. Si diffusion in this regime was described by: E$\sb{\rm diff,Si}$ = 23 kcal/mol and D$\rm\sb0\Delta C$ = $\rm 5\times10\sp{-17}\ cm\sp{-1}\ s\sp{-1}$.
Issue Date:1994
Rights Information:Copyright 1994 Mendicino, Michael Anthony
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9543791
OCLC Identifier:(UMI)AAI9543791

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