In this study, electromigration ͑EM͒ characteristics of Cu line and nickel ͑Ni͒-silicide on Cu-line/W-via/Ni-silicide structure were compared. The experimental results revealed that EM competition of Cu line depletion and Ni-silicide migration depends on the length of Cu line and the stress current density. For a longer Cu line or stress at a higher current density, the failure time of Cu-line depletion is lower than that of Ni-silicide migration because the failure mode is Cu-line depletion. On the other hand, as the length of Cu line is decreased and stressed at a lower current density, the failure mode is transferred to Ni-silicide migration due to a stronger back-stress effect in a shorter Cu line. The critical current densities ͑ j c ͒, activation energy ͑E a ͒, and current density exponent ͑n͒ values for Cu-line depletion mode and Ni-silicide migration modes were characterized, which are used to predict the EM lifetime at normal operation conditions. The results indicated that although the failure time of Ni-silicide migration mode is lower than that of Cu-line depletion mode for a shorter Cu line at a higher stress temperature, Ni-silicide migration with a higher activation energy ͑ ϳ 1.7 eV͒ results in a longer EM lifetime at a lower operation temperature.Electromigration ͑EM͒ has been recognized as one of the most severe reliability concerns in integrated circuits ͑ICs͒ as the features of ICs are scaled down to submicrometer dimension. 1,2 One of the EM improvement strategies to increase the current limit is to use the short metal lines. 3-5 Although the shorter lead can significantly increase EM reliability, this benefit may disappear if another EM failure mode appears earlier due to different metal materials or interfaces.Most studies reported the short length effect of Cu line according to Cu-line/Cu-via/Cu-line structures fabricated by a dual-damascene technology. 4-7 These results are appropriate for global interconnect EM reliability assessment, but not for local interconnect because connected via and underlying metal are changed to tungsten ͑W͒ and silicide polysilicon.In this study, we present EM results of Cu lines connected to Ni-silicide underlying layer through W-via varying the length of Cu line. The effects of the Cu line length and stress current density on EM characteristics are emphasized. Finally, the predicted EM lifetime at different operation current densities and temperatures for different EM failure modes is presented as well. ExperimentalThe EM test structures consisting of Cu metal line of 10-250 m length and 0.10 m width were evaluated in this study as shown in Fig. 1. The Cu lines connect to a Ni-silicide layer in the underlying polysilicon line through W-vias. The Cu interconnects were embedded in low-k ͑k = 2.8͒ dielectric and processed with a SiCN capping layer. The dimension of the W-via hole is 0.09 m. The length and width of the polysilicon line are 1.2 and 0.17 m, respectively. The formation thickness of the Ni-silicide layer is about 25 nm. The stress current density is...

Hexagonally arranged Au nanoparticles exhibiting a broad Gaussian-shaped size distribution ranging from 30 nm to 80 nm were deposited on Si substrates and irradiated with Ar + and Ga + ions with various energies from 20 to 350 keV and 1 to 30 keV, respectively. The size and energy dependence of the sputter yield were measured using high-resolution scanning electron microscopy image analysis. These results were compared to simulation results obtained by iradina, a Monte Carlo code, which takes the specifics of the nano geometry into account. The experimental sputter yields are significantly higher than simulated sputter yields for both bulk and the nano geometry. The difference can be clearly attributed to thermally driven effects, which significantly increase the measured sputter yields.