Modeling Copper Diffusion in Silicon Oxide, Nitride, and Carbide

Density functional theory was applied to simulate copper diffusion in silicon oxide, nitride, and carbide (SiO x , SiN x , SiC x ). Because copper drift into oxide is significantly enhanced by negative bias, copper ions are the active diffusing species. Clusters and, in some cases supercells, modeling various ring configurations of the amorphous networks of silicon oxide, nitride, and carbide were employed. Interactions of both neutral copper and its cation, Cu + , with the network were explored. Calculations revealed a strong binding of Cu + to SiO x , SiC x , and SiN x in contrast with neutral Cu. The Cu+ attraction to carbide clusters is significantly lower than to SiO x and SiN x , explaining the effective barrier properties of SiC x . The estimated lower bounds for activation energies for Cu + hops between stable ring clusters of SiO x and SiN x are similar. This implies that the difference in Cu diffusion properties between oxides and nitrides is likely due to a higher percentage of large rings in amorphous oxides compared with nitrides. An approach to increasing the resistance of oxides to Cu + diffusion is suggested.