Mechanisms of Methyl Group Elimination from Low-K Dielectric Surfaces by Plasma of Various Composition
摘要
Dielectrics with ultralow dielectric permittivity (so-called “low-k” materials) are used as interlayer insulators for copper conductors in ultra-large-scale integrated circuits. The diffusion of copper atoms can degrade their properties, and the most effective approach to mitigate this issue is to form ultrathin metallic barrier layers on their surface. However, this process is hindered by the complex surface topology of low-k films and the presence of hydrophobic CH3 groups, which obstruct metal deposition. Therefore, surface pre-functionalization is required before layer deposition, with the primary goal of removing methyl groups. In this work, dynamic simulations based on density functional theory were carried out to study the effect of plasma radicals and ions of various compositions (inert gases, molecular nitrogen, and oxygen) on the surface of a low-k dielectric in order to investigate the mechanisms by which these particles remove methyl groups. The results demonstrate that this process can proceed at relatively low particle energies (10–15 eV). The study presents a detailed analysis of calculated particle trajectories, compares the interaction of CH3 groups with inert gas atoms (Ne and He) and with more chemically active nitrogen and oxygen atoms, and describes the specific features of group removal under the action of molecules and molecular ions.