A molecular dynamics model for the interaction of energetic ions with SiOCH low-κ dielectric

Abstract

A molecular dynamics model is used to investigate the interaction of energetic ions with fluorocarbon passivated Si, O, C, and H (SiOCH) based low-κ dielectrics. The model includes a set of interatomic potentials required for the SiOCH–CFx interaction system, where the two- and three-body pseudopotentials have either been obtained from published literature or computed using ab initio techniques. The test structure used for the ion interaction simulations is put together through deposition of low energy SiOx+, CHy+, and H+ ions on a crystalline Si substrate. A thin fluorocarbon passivation layer is grown on the low-κ test structures by bombarding them with moderate energy CFx+ ions. Simulations of CF2+ ion interaction with the fluorocarbon passivated SiOCH samples show that the sputter yield of sample constituents (Si, O, and H) increases with ion energy and peaks at about 60°. H sputters more easily compared to other species, and the surface layer is expected to become H deficient over time. Sputtered H atoms are also generated over a broader region near the surface compared to other species. Most sputtered clusters with origin in the bulk film are ejected with energies less than 10eV and their angular and energy distributions are not sensitive to the energy or angle of the incident ion. Incident CF2+ ion breaks apart on contact with the test structure and, at high energies and near normal incidence, virtually no CF2 reflects back from the sample. Fragments of the incident ion have reflectionlike properties: peak in angular dependence function shifts towards larger angles as ion angle of incidence increases and reflected fragments are more energetic as ion angle of incidence increases. Comparison of CF2+ ion etching properties of SiOCH low-κ dielectric with SiO2 shows that more atoms are sputtered from SiOCH under identical conditions. However, as many of the sputtered atoms from the SiOCH material are light H atoms, mass etch yield from SiOCH and SiO2 is comparable. Si and O are both found to sputter more easily from SiOCH relative to SiO2. SiOCH low-κ ion etching properties are compared for several ions (CFx+, CHFy+, SiFz+, and Ar+). Results show that the etch yield from F containing ions is larger than that of Ar+, and the etch yield increases as the F content of the ion increases. Comparison of the ion etching properties of porous and nonporous low-κ dielectrics shows that, under similar conditions, the fluorocarbon passivation layer is thicker on the porous material. Due to this thicker passivation layer, mass yield from the porous dielectric material is smaller for the same ion energy.

Molecular dynamics for low temperature plasma–surface interaction studies

“…The question of film formation, surface modification and etching was addressed by Kawase and Hamaguchi [2007] A similar study was reported by Smirnov et al [2007] for an important low dielectric constant ('low-κ') material, containing Si, C, O and H ('SiCOH'). These authors found that a FC passivation layer forms in the near-surface region when impacting their model dielectric film with CF x ions.…”

Effect of energetic ions on plasma damage of porous SiCOH low-k materials

“…27,28 Recent attempts to separate the contribution of different plasma components demonstrated the complicated nature of this phenomena. [16][17][18] For instance, a quite efficient sealing of pores in some cases can be achieved by combined effects of chemical, photochemical, and ion stimulated processes. 32,33 Some authors 27,28 reported that the plasma damage reduction can be related to removal of the degraded layer by the oxygen ions due to the high chemical sputtering rate.…”

“…This is the reason why significant efforts by researches are presently oriented to a separate study of VUV photons, energetic ions, and radicals impact on plasma damage of low-k materials. [15][16][17][18] Although quite significant understanding of different factors has been achieved, the studies in the references are based on special tools and instrumentations.…”

Pore sealing mechanism in OSG low‐k films under ion bombardment

“…Currently, computer simulation can be considered as an effective tool to give an appropriate interpretation of obtained experimental results and to reveal the mechanisms of the processes under investigation. The Monte Carlo (MC) and molecular dynamics (MD)‐based modeling were applied to study effects of the surface roughness and the presence of nanosized structural objects on the sputtering yield, and some important features of these phenomena were explained . To investigate structural changes in nanoporous materials due to ion bombardment, an atomistic approach is needed as it is necessary to analyze trajectories of all atoms, to take into account the energy deposited by incident ions and the excess energy of atoms located on pore walls as well as to consider the possibility of phase transitions caused by the fast energy release.…”