Electromigration tests on different Cu dual-damascene interconnect tree structures consisting of various numbers of straight via-to-via lines connected at the common middle terminal have been carried out. Like Al-based interconnects, the reliability of a segment in a Cu-based interconnect tree strongly depends on the stress conditions of connected segments. The analytic model based on a nodal analysis developed for Al trees gives a conservative estimate of the lifetime of Cu-based interconnect trees. However, there are important differences in the results obtained under similar test conditions for Al-based and Cu-based interconnect trees. These differences are attributed to the variations in the architectural schemes of the two metallization systems. The absence of a conducting electromigration-resistant overlayer in Cu technology and the low critical stress for void nucleation at the Cu/inter-level diffusion barrier (i.e. Si₃N₄) interface leads to different failure modes between Cu and Al interconnects. As a result, the most highly stressed segment in a Cu-based interconnect tree is not always the least reliable. Moreover, the possibility of liner rupture at stressed dual-damascene vias leads to significant differences in tree reliabilities in Cu compared to Al. While an interconnect tree can be treated as a fundamental unit whose reliability is independent of that of other units in Al-based interconnect architectures, interconnect trees can not be treated as fundamental units for circuit-level reliability analyses for Cu-based interconnects. / Singapore-MIT Alliance (SMA)
| Identifer | oai:union.ndltd.org:MIT/oai:dspace.mit.edu:1721.1/3730 |
| Date | 01 1900 |
| Creators | Gan, C.L., Thompson, Carl V., Pey, Kin Leong, Choi, Wee Kiong |
| Source Sets | M.I.T. Theses and Dissertation |
| Language | en_US |
| Detected Language | English |
| Type | Article |
| Format | 180049 bytes, application/pdf |
| Relation | Advanced Materials for Micro- and Nano-Systems (AMMNS); |
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