Decomposition Chemistry of Tetraethoxysilane

SiO ₂ 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 SiO ₂ 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 SiO ₂ . Equilibrium constants for the gas‐phase intermediate formation and surface adsorption respectively are 1.38 × 10 ¹⁰ exp[(– 299.24 kJ/mol)/ RT ] and 1.14 × 10 ⁴ exp[(– 21.80 kJ/mol)/ RT ]. The rate constant for the surface decomposition of the intermediate is 1.29 × 10 ⁻⁶ 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 be used instead of aluminum metallization.