Decomposition Chemistry of Tetraethoxysilane

Abstract

Si02 films deposited by the decomposition of tetraethoxysilane (TEOS) at high temperatures have superior insulating properties and excellent step coverage, but are not compatible with aluminum metallization. Earlier work on the deposition of SiOt from TEOS concentrated on the properties of the film and on the modeling of thickness uniformity, but no attempt was made to probe the decomposition chemistry. In the present work a three-step model is presented to explain the TEOS deposition chemistry. A useful deposition temperature is determined by the first step where an intermediate is formed in the gas phase. This activated species adsorbs on the surface and later decomposes into Si02. Equilibrium constants for the gas-phase intermediate formation and surface adsorption respectively are 1.38 X 10" exp[( -299.24 kJ/ mol)/RT] and 1.14 x lo4 exp[( -21.80 W/mol)/RT]. The rate constant for the surface decomposition of the intermediate is 1.29 X exp[( -12.26 kJ/mol)/RT]. This model successfully explains rate dependence on pressure and temperature. Approaches are suggested which would catalyze the formation of the activated species and thus lower the deposition temperature such that this process could he used instead of aluminum metallization. [

The pyrolytic decomposition of aluminium-tri-sec-butoxide during chemical vapour deposition of thin alumina films

“…The free radical mechanism has been discussed by, amongst others, Desu [22] and Barybin and Tomilin [23], investigating the decomposition chemistry of tetraethoxysilane (TEOS) and ATI, respectively. The free radical mechanism for AT1 was based on the energy of displacement of electron pairs in the polar M-O bond [23,241 and on the dissociation energy of the Al-O and 0-C3H7 bonds [23].…”

“…The free radical mechanism for AT1 was based on the energy of displacement of electron pairs in the polar M-O bond [23,241 and on the dissociation energy of the Al-O and 0-C3H7 bonds [23]. Desu [22] used the bond energies within the TEOS molecule to explain the free radical mechanism. Figure 5 shows the details of the decomposition reaction of ATSB, assuming a free radical mechanism based on data from Desu [22] and Barybin and Tomilin [23].…”

“…Desu [22] used the bond energies within the TEOS molecule to explain the free radical mechanism. Figure 5 shows the details of the decomposition reaction of ATSB, assuming a free radical mechanism based on data from Desu [22] and Barybin and Tomilin [23]. It is suggested that the metal alkoxides form oligomers due to bridge formation of the alkoxide groups (between oxygen and the metal).…”

“…The decomposition path of the a-hydride elimination, based on data from Desu [22], is presented in Fig. 7.…”

Localized planarization of optical damage using laser-based chemical vapor deposition

“…A two-step reaction pathway is assumed where an intermediate is first formed through decomposition of the silica precursor (TEOS) in the gas phase, which then transports and reacts at the surface under a separate chemical kinetic rate equation. 13,14 Although the decomposition of TEOS in various environments is known to involve several reaction pathways, we further simplify our model by neglecting details of the radical formation kinetics and volatile species reaction, and simply express the dominant first order reactions as: (2) Note that the reactions above are taken to be irreversible and that the byproducts under similar operating conditions will include several alky-and hydroxyl-rich species such as ethane, ethanol and diethylether O(C 2 H 5 ) 2 (DEE). 15 For the purposes of the simulation we select to model the byproducts as only the DEE, since the exact identity of the byproducts will not significantly affect either the deposition kinetics or the prediction of deposition rates.…”