We investigated the effects of Cu-line layouts on plasma-induced radiation damage (PRD) to interline low-k dielectric films. We carried out a finite-element-method-based three-dimensional (3D) electromagnetic simulation (EMS), in which a Drude free-electron model was implemented for the dielectric function of Cu lines. The 3D EMS analysis revealed that the electric field in the low-k films was enhanced for specific Cu-line layouts exposed to N2 plasma irradiation, while no clear electric-field enhancement was observed for Ar plasma exposure. The specific optical emission lines produced in N2 plasmas are the root cause of damage creation in the low-k dielectric films with embedded Cu lines. The 3D EMS analysis predicted that the electric field was enhanced with decreasing the line and space (L/S) widths. The prediction implies that the Cu-line-layout dependent PRD should be more prominent as device dimensions shrink. We verified the predicted results experimentally using devices with low-k films between various L/S Cu lines, in addition to a blanket wafer—without Cu lines. We found that an increasing peak in the low-k dielectric constant appeared at a specific L/S width after N2 plasma exposure and no clear increase in the dielectric constant was observed after Ar plasma exposure. The obtained experimental results are consistent with the 3D EMS analysis. We propose a damage model, where the electric field enhancement plays an important role in the low-k dielectric films with embedded Cu lines. The proposed damage model is indispensable for minimizing PRD and designing Cu layouts in future devices.
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