Kinetics of Silane Decomposition in High-Pressure Confined Chemical Vapor Deposition of Hydrogenated Amorphous Silicon

Abstract

We study the kinetics of silane pyrolysis via confined high-pressure chemical vapor deposition (HPCVD) at pressures of 20−33 MPa in a microcapillary of 5.9 μm inner diameter. We find the growth rate to be first order with respect to silane concentration, with an activation energy of 53.7 ± 2.9 kcal/mol and a pre-exponential factor of 1.5 × 10 10 m/s. The obtained activation energy is in the range of activation energies reported for hydrogen desorption from c-Si surfaces, suggesting that hydrogen desorption from the surface is the ratelimiting step in film growth. To further investigate this finding, reactive molecular dynamics simulations of thermal decomposition of silane on clean and hydrogen-passivated c-Si were performed. Homogeneous reactions were not observed in any of the simulations, in support of the hypothesis that heterogeneous silane decomposition on the silicon surface is the dominant mechanism for film deposition. In silane pyrolysis simulations on clean c-Si surfaces, almost all available silicon surface sites (i.e., dangling bonds) were occupied by silicon-hydrides (mostly tri-and dihydrides) upon exposure to gas-phase silane, whereas no reaction was observed during silane decomposition simulations on the hydrogen-passivated c-Si. Therefore, the results of the reactive molecular dynamics simulations indicate that the availability of dangling bonds resulting from hydrogen desorption from the surface is the rate-limiting step in film growth at high pressure.

Controlled Silanization: High Molecular Regularity of Functional Thiol Groups on Siloxane Coatings

“…The model is based on the following assumptions: (1) The attachment of organosilicon is irreversible due to the formation of chemical bonds with substrates. 30 (2) Adsorption does not proceed beyond the monolayer coverage during the experimental time span. (3) Activities of all sites are equivalent.…”

“…In order to compare the deposition kinetics of two organosilicon compounds, the thicknesses were converted into surface fractional coverage, θ, and fitted by a simple adsorption isotherm, as described in Materials and Methods. The model is based on the following assumptions: (1) The attachment of organosilicon is irreversible due to the formation of chemical bonds with substrates . (2) Adsorption does not proceed beyond the monolayer coverage during the experimental time span.…”

Real-Time Zeta Potential Analysis of Microchannel Surfaces during Aminosilane Deposition and Exposure Using Current Monitoring

“…In future work, we propose to investigate the effects of transport conditions (e.g., flow rate, capillary diameter, silane concentration) on APS coating kinetics and final coverage, which was previously only examined for vapor-phase depositions. 51 ■ ASSOCIATED CONTENT * sı Supporting Information…”

“…These preliminary results substantiate AZA as a robust, fully automated method for analyzing the zeta potential at high resolution during surface coating and degradation processes. In future work, we propose to investigate the effects of transport conditions (e.g., flow rate, capillary diameter, silane concentration) on APS coating kinetics and final coverage, which was previously only examined for vapor-phase depositions …”

Reactive force field simulations of silicon clusters

“…This synergistic combination had an improved performance in terms of computational speed and accuracy and was capable of reproducing fractures (by means of the ReaxFF component) and elastic deformations (by means of the Tersoff representation) of silicon accurately [5,6]. Other studies explored the behaviour of silicon-based compounds such as silicon carbide [7,8], silanes [9], silicates [10,11], whereas more recent investigations were focused on the functionalization of silicon surfaces with organic molecules [12,13]. It follows that silicon parameters can be found in many different ReaxFF force fields, also because silicon is contained in various types of composites [14].…”