Plasma charging damage issues in copper single and dual damascene, oxide and low-k dielectric interconnects

We compared plasma charging damage in single and dual damascene copper wafers with that in classical aluminum back-end-of-line (BEOL) wafers at different antenna levels. In contrast to earlier publications, this comparison is not straightforwardly in favor of the damascene BEOL, but rather depends on the process module (i.e. antenna) under consideration. Contact level antennas suffer from more damage in a (single) damascene BEOL as they are sensitive to a larger number of potentially harmful steps. At first glance, via antennas show a better plasma process-induced damage (P2ID) performance than their classical counterparts. However, the layout of a metal trench grid on top of the contact or via holes has a strong impact on P2ID. Considerable damage is still created at the damascene metal-1 level, but it is of a different origin than in an Al BEOL. With respect to the impact of some damascene-specific process steps and materials, it was found that the introduction of novel low-k materials in the IMD stack does not create appreciable changes in P2ID behavior. On the other hand, Cu-barrier sputter deposition might be an issue