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

A molecular dynamics model is used to investigate the interaction of energetic ions with fluorocarbon passivated Si, O, C, and H (SiOCH) based low-kappa 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-kappa 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 degrees . 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 10 eV 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-kappa 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-kappa 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-kappa 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. (c) 2007 American Institute of Physics.