Electromigration (EM) remains a major reliability concern for on-chip Cu interconnects due to the continuing scaling and the introduction of new materials and processes. In Cu interconnects, the atomic diffusion along the Cu/SiCN cap interface dominates the mass transport and thus controls EM reliability. The EM lifetime degrades by half for each new generation due to the scaling of the critical void volume which induces the EM failure. To improve the EM performance, a metal cap such as CoWP was applied to the Cu surface to suppress the interfacial diffusion. By this approach, two orders of magnitude improvement in the EM lifetime was demonstrated. For Cu lines narrower than 90 nm, the Cu grain structure degraded from bamboo-like grains to polycrystalline grains due to the insufficient grain growth in the trench. Such a change in Cu grain structures can increase the mass transport through grain boundaries and thus degrade the EM performance. The objective of this study is to investigate the scaling effect on EM lifetime and Cu microstructure, and more importantly, the grain structure effect on EM behaviors of Cu interconnects with the CoWP cap compared to those with the SiCN cap only. This thesis is organized into three parts. In the first part, the effect of via scaling on EM reliability was studied by examining two types of specially designed test structures. The EM lifetime degraded with the via size scaling because the critical void size that causes the EM failure is the same with the via size. The line scaling effect on Cu grain structures were identified by examining Cu lines down to 60 nm in width using both plan-view and cross-sectional view transmission electron microscopy. In the second part, the effect of grain structure was investigated by examining the EM lifetime, statistics and failure modes for Cu interconnects with different caps. A more significant effect of the grain structure on EM characteristics was observed for the CoWP cap compared to the SiCN cap. For the CoWP cap, the grain structure not only affected the mass transport rate along the Cu line, but also impacted the flux divergence site distribution which determined the voiding location and the lifetime statistics. Finally, the effect of grain structure on EM characteristics of CoWP capped Cu interconnects was examined using a microstructure-based statistical model. In this model, the microstructure of Cu interconnects was simplified as cluster and bamboo grains connected in series. Based on the weakest-link approximation, it was shown that the EM lifetime and statistics could be adequately modeled by combining the measured cluster length distribution with the EM lifetime-cluster length correlation for each individual failure unit. / text

Les problématiques d’économie d’énergie et de diminution des pertes illustrent les limites du Si dans les composants de puissance actuels. Face à ces besoins, le GaN constitue un bon candidat pour la réalisation de nouveaux composants comme les diodes Schottky de puissance. Ainsi, le GREMAN et STMicroelectronics ont entamé une collaboration visant à réaliser une diode Schottky capable de tenir une tension de – 600 V. Or, de nombreux verrous, tels que la forte sensibilité du GaN à la température et les difficultés d’activation de zones localisées dopé de type p (Mg) subsistent encore. Cependant, nous avons mis en évidence l’efficacité de la cap-layer USG/AlN pour la protection du GaN à haute température. Concernant l’activation des dopants de type p par implantation, nous avons démontré que la réduction du « channeling » du Mg nécessite les conditions d’implantation particulière : un tilt de 10° et une épaisseur d’oxyde (USG) de pré-implantation de 200. Parallèlement, nous avons étudié deux procédés d’activation par recuit RTA, mono- et multicycles, et montré leur utilité pour l’activation du dopant. Néanmoins, ce dernier point reste à approfondir. / Energy saving and reduction of losses issues illustrate the current limits of the Si for power devices. To face these needs, GaN is a good candidate for the realization of new components such as Schottky power diodes. GREMAN and STMicroelectronics have worked together to achieve such diodes with 600 V or more breakdown voltages. However, many mandatory milestones, such as GaN temperature sensitivity and the activation problems of localized p-type doped (Mg) zones, must be faced. In this work, we have demonstrated the efficiency of an USG/AlN cap-layer for the protection of GaN facing high-temperature annealing. Concerning the capability to obtain p-type doping by ion implantation, we demonstrate that the reduction of Mg "channeling" effect is achievable using the following conditions: a tilt of 10° and a screening layer (USG) with a thickness of 200 nm. Meanwhile, we have illustrated two activation processes using RTA: single- and multi-cycles annealing. However, activation, after implantation and annealing, has to be investigated in more details.