Plasma-induced photon irradiation damage on low-k dielectrics enhanced by Cu-line layout

We demonstrate experimentally and theoretically the existence of circuit-layout-dependent low-k damage by plasma radiation. Circuit-layout-dependent low-k damage apparently occurs in nitrogen (N₂) plasma, not in argon (Ar) plasma. Using an electromagnetic simulation and the dispersion analysis, we reveal that E-field in the low-k film is enhanced for specific Cu-line layouts in the case of N₂ plasma. The results of electromagnetic simulations and dispersion analysis are consistent with the obtained experimental results. We propose a new low-k damage model, where "near-field" by the irradiated copper lines plays an important role in the damage creation. The near-field enhances E-field in the low-k film, accelerating the bond-breakage, i.e., the dielectric constant increase. The present model framework is useful for optimizing an integrated circuit layout, simultaneously minimizing the plasma radiation damage.