On the Dissociative Chemisorption of Tris(dimethylamino)silane on Hydroxylated SiO₂(001) Surface

Abstract

We present a first-principles theoretical study on the dissociative chemisorption of tris(dimethylamino)silane (TDMAS) on a hydroxylated SiO 2 (001) surface. The thermochemical energies and activation barriers associated with the elementary surface reaction processes have been calculated. Our results indicate that sequential dissociation of TDMAS can occur only up to the second step with dimethylaminosilylenyl groups anchored on the surface. Further dissociation of these surface species is virtually energetically forbidden under typical atomic layer deposition processing conditions. This would result in an inherently low density and compositionally impure SiO 2 film with a low deposition rate.

First-Principles Study of a Full Cycle of Atomic Layer Deposition of SiO2Thin Films with Di(sec-butylamino)silane and Ozone

“…The more exposed type was found previously to be more reactive than the embedded one. 21 The higher electron density on O1, coupled with the high surface exposure of the atom, makes the O1 sites more accessible for electrophilic attack by precursor molecules. The optimized DSBAS molecule is shown in Figure 2.…”

Impact of Aminosilane Precursor Structure on Silicon Oxides by Atomic Layer Deposition

“…Again, the step is not expected to be kinetically controlled due to the modest (10-20 kcal/mol activation energies found for TDMAS and BTBAS 11,12 ). It also must be noted that the second amine desorption is more difficult energetically than the first one for all three precursors, probably due to the more acidic nature of the remaining silicon species.…”

“…10 A periodic surface slab model was used to mimic the hydroxylated SiO 2 substrate (100) surface as described in detail elsewhere. 11,12 The PW91 gradient corrected density functional 13 was used in conjunction with a double polarized numerical localized basis set and all electron approximation as implemented in the Dmol 3 module 14 in Materials Studio.…”

“…In recent studies by Li et al 11 it was demonstrated that in contrast with the removal of first and second amine substituents, the third amine removal sequence, as required for TDMAS, is kinetically very difficult. The reaction appears to have a very high activation energy (70-90 kcal/mol depending on orientation), which makes the complete removal of the amine groups from the films exceedingly challenging.…”

Electrical behavior of atomic layer deposited high quality SiO2 gate dielectric

“…Much effort has therefore been made to increase the GPC of ALD SiO 2 thin films, while maintaining the quality of the deposited films. 10,11 These precursors first undergo sequential dissociative chemisorption on a hydroxylated SiO 2 surface, resulting in anchoring of the Si atom of the precursors on the surface and the release of amines to the gas phase. 7 The chemical reaction of the precursors only occurs at the film surface, so conformal growth of SiO 2 films is enabled on complex three-dimensional structures.…”