AbstractElectromigration experiments have been carried out on simple Cu dual-damascene interconnect tree structures consisting of straight via-to-via (or contact-to-contact) lines with an extra via in the middle of the line. As with Al-based interconnects, the reliability of a segment in this tree strongly depends on the stress conditions of the connected segment. Beyond this, there are important differences in the results obtained under similar test conditions for Al-based and Cu-based interconnect trees. These differences are thought to be associated with variations in the architectural schemes of the two metallizations. The absence of a conducting electromigrationresistant overlayer in Cu technology, and the possibility of liner rupture at stressed vias lead to significant differences in tree reliabilities in Cu compared to Al.
Abstract
This paper examines copper-interconnect integrated circuit transmission electron microscope (TEM) sample contamination. It investigates the deterioration of the sample during ion milling and storage and introduces prevention techniques. The paper discusses copper grain agglomeration issues barrier/seed step coverage checking. The high temperature needed for epoxy solidifying was found to be harmful to sidewall coverage checking of seed. Single beam modulation using a glass dummy can efficiently prevent contamination of the area of interest in a TEM sample during ion milling. Adoption of special low-temperature cure epoxy resin can greatly reduce thermal exposure of the sample and prevent severe agglomeration of copper seed on via sidewall. TEM samples containing copper will deteriorate when stored in ordinary driers and sulphur contamination was found at the deteriorated point on the sample. Isolation of the sample from the ambient atmosphere has been verified to be very effective in protecting the TEM sample from deterioration.
Control of solidification structure and crystallographic texture during metal additive manufacturing is a challenging work which attracts the increasing interest of researchers. In the present work, two kinds of scanning strategies (i.e., single-directional scanning (SDS) and cross-directional scanning (CDS) were used to control the solidification structure and crystallographic texture during quasi-continuous-wave laser additive manufacturing (QCW-LAM) of Inconel 718. The results show that the solidification structure and texture are strongly dependent on scanning strategies. The SDS develops a typical fiber texture with unidirectional columnar grains, whereas the CDS develops a more random texture with a mixture of unidirectional and multidirectional grains. In addition, the SDS promotes the continuously epitaxial growth of columnar dendrites and results in the linearly distributed Laves phase particles, while the CDS leads to the alternately distributed Laves phase particles with chain-like morphology and discrete morphology. The changed stacking features of molten-pool boundary and the switched heat flow direction caused by different scanning strategies plays a crucial role on the epitaxial growth of dendrites and the final solidification structure of the fabricated parts.
A Simplified Yield Criterion of the Orthotropic Material Considering the Crystallographic Texture