Reactivity of Fluorinated Si(100) with F₂

Abstract

The dissociative chemisorption of F 2 on the Si(100)(2 × 1) surface saturated with 1 monolayer (ML) of fluorine is investigated as a function of the incident F 2 translational energy. At energies below 3.8 kcal/mol, no reaction with the Si-Si bonds occurs. Above this threshold, the probability of dissociative chemisorption rises linearly with the normal component of the incident translational energy up to a value of 3.6 × 10 -3 at 13 kcal/mol. The relatively small effect of translational energy implies a late barrier in the potential energy surface for the interaction of F 2 with the Si-Si bonds. These probabilities are measured by exposing the fluorine-saturated surface to supersonic F 2 beams of variable energy, followed by thermal desorption measurements to determine the resulting fluorine coverage. Information regarding the specific Si-Si site (Si-Si dimer or Si-Si lattice bonds) at which the translationally activated reaction occurs is obtained from He diffraction measurements. The intensity of the diffracted beams is monitored after exposing the fluorinesaturated surface to F 2 of variable energy. The intensities remain constant after exposure to low-energy (<3.8 kcal/mol) F 2 , whereas they decline monotonically as a function of F 2 normal energy above the 3.8 kcal/mol threshold. Moreover, the similarity of the relative cross sections for diffusive scattering measured after exposure to translationally fast F 2 to those measured after Ar + ion bombardment strongly suggests that the reaction does not occur preferentially at the Si-Si dimer bonds, which are the weakest Si-Si bonds in the system. Reaction at Si-Si lattice bonds also occurs, leading to surface disorder. Additional data show that for submonolayer coverages generated from low energy F 2 , no reaction with Si-Si bonds occurs, while exposure to high-energy F 2 leads to reaction with Si-Si bonds.

Atomic-scale study of the adsorption of calcium fluoride on Si(100) at low-coverage regime

“…This implies that the silicon surface is partially etched during the adsorption of the CaF 2 molecules, which is consistent with the work of Pasquali et al 11 The removal of the silicon dimers in the presence of F 2 molecules is often explained via the formation of SiF 2 species. [30][31][32] Although the purpose of this paper is not a a a a a a a a a a a a a a a focused on the dynamics of the CaF 2 reactivity on the Si(100) surface, we can draw a simple scenario for the fabrication of the observed unit cell if we assume that the Si(100) surface is etched similarly with F 2 or CaF 2 molecules. Therefore, we assume that, preliminary to the silicon etching process with CaF 2 , the silicon surface requires a passivation of the silicon dimer with F atoms according to the etching process with F 2 molecules 31 such that:…”

Mechanism and dynamics of the reaction of XeF2 with fluorinated Si(100): Possible role of gas phase dissociation of a surface reaction product in plasmaless etching

“…The exposure time is calibrated to absolute coverage by comparing the SiF 4 and SiF 2 signals measured in a thermal desorption experiment to those resulting from a known fluorine coverage, 0.94Ϯ 0.11 ML F atoms, as described previously. 40,49…”

Mechanism behind dry etching of Si assisted by pulsed visible laser

“…Similarly, Jeng's 21 work in rapid thermal processing of F þ -implanted Si shows that fluorine will reliably segregate to the surface, affirming that the drop in the surface F content measured by XPS is due to SiF x desorption, rather than F diffusing into the bulk wafer. Further corroborating this, desorption of SiF x at high temperatures was measured by Pullman 22 through residual gas analysis and calculated in MD simulations by Tinck. 23 Two Si samples were prepared in a brief, no-bias Ar/SF 6 etch at room temperature.…”