A theoretical study of adsorption equilibria in silicon CVD

Abstract

As part of a theoretical study of adsorption processes in the chemical vapour deposition of silicon, thermochemical data are derived for the adsorption of Si-H species on the Si(111) and the dimer-reconstructed Si(001)-(2 xl) surfaces. Essential contributions to the heats of adsorption appear to be electron pairing and two-and three-body interactions. It is shown that when the bond energies are defined in this way, also a consistent description of the bonds in silicon hydrides is provided. This demonstrates that with reasonable confidence the method can be applied to the adsorption process itself. Data are derived for species which may form one, two or even four bonds with the surface. It is assumed that on the (111) surface adsorbates bind on the "dangling bonds" which are present on this surface in a broken bond model. It is demonstrated that on the dimer reconstructed Si(001)-(2 xl) surface, adsorbates will either bind on the surface atoms with one or two bonds, without the breaking of the dimer bonds, or, if the species have the possibility to form two or four bonds with the surface atoms, may become inserted into the dimer bonds. With the aid of the derived thermochemical data for adsorption and the Langmuir isotherm or modifications thereof, the coverage of the Si(111) and the dimer reconstructed Si(001)-(2X1) surfaces with species from the Si-H system is calculated. It is found that the equilibrium surface coverages of the Si(111) and the Si(001)-(2 xl) surfaces are very similar: the hydrogen coverage is high at all temperatures, while at low supersaturation the coverage with growth species is very low on both surfaces.

Kinetic Study of the Chemical Vapor Deposition of Tantalum in Long Narrow Channels

“…These are also consistent with the values found in literature pertaining to other CVD systems. Gardeniers et al have done comprehensive studies on the adsorption of different silicon chlorides and hydrides onto silicon with respect to the CVD of silicon, and have found adsorption enthalpies and entropies quite similar to those found in this work. Values are also consistent with Giling's work …”

“…The reactant species come into closer physical alignment once adsorbed onto a surface thus requiring less activation energy to react. It is for this reason that surface CVD by several authors is modeled similarly to heterogeneous catalysis systems, i.e., using Langmuir's adsorption–desorption kinetics.…”

Low-Temperature LPCVD of Polycrystalline Ge[sub x]Si[sub 1−x] Films with High Germanium Content

“…The difference in growth rate can be explained, e.g., by dissimilar adsorption-desorption for various crystal planes. 54,55 All crystals during their evolution will finally be bound by the thermodynamically most stable plane, which is the ͑111͒ plane. The growth rate in the ͑111͒ direction is the lowest compared to the growth rates in the other possible directions.…”

A study of morphology and texture of LPCVD germanium-silicon films

“…The difference in growth rate can be explained e.g. by dissimilar adsorptionrelated matters for various crystal planes [16,17].…”