Mechanisms of Methyl Group Elimination from Low-k Dielectric Surfaces by Plasma of Various Composition

Low-k dielectrics are applied as interlayer isolators between metallic (cuprum) interconnects in very large integrated circuits. Diffusion of Cu atoms can lead to their degradation, and the most efficient way to solve this problem is the fabrication of ultra-thin metal barrier layers. However, this process is complicated by the non-flatness of low-k surface and the presence of hydrophobic CH-groups preventing the metal deposition. Therefore, before the barrier coating it is necessary to perform preliminary surface fuctionalization aimed at removing methyl groups. In this work the dynamic density functional theory-based simulation of radical and ion irradiation of low-k surface for plasma of various composition (noble gases, molecular nitrogen and oxygen) was carried out to study the mechanisms of methyl group removal. The results obtained showed the possibility of this process for low-energy range (10-15 eV) of incident particles. In this work the detailed analysis of the calculated trajectories is presented, the interactions of CH-groups with noble gas atoms (Ne, He) and with more chemically active N and O atoms were compared, the peculiarities of methyl group removal under molecule and molecular ion irradiation were described.