Electromigration Mechanisms of VLSI Multilevel Interconnects.
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Accession number;99A0938081
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| Title;Electromigration Mechanisms of VLSI Multilevel Interconnects. |
| Author;
KAWASAKI HISAO
(Tohoku Univ.)
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Journal Title;Record of Electrical and Communication Engineering Conversazione, Tohoku University
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Journal Code:F0511A
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ISSN:0385-7719
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VOL.68;NO.1;PAGE.61-64(1999)
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| Figure&Table&Reference;FIG.5, REF.7 |
| Pub. Country;Japan |
| Language;Japanese |
| Abstract;In this study, it has been shown that electromigration failures are significantly influenced by the test structures and stress conditions. For better estimation of the lifetime of VLSI interconnects at operating conditions, it has been demonstrated that data must be taken using test structures designed to minimize structural effects, namely effects of reservoir, stress-induced Al backflow and Joule heating. In modern multilevel metallization schemes, it has been shown that Al-Cu interconnects fail through mainly two stages, incubation stage and Al depletion stage. This incubation time, before which no electromigration induced Al depletion starts, was found to be time period during which Cu atoms in Al-Cu alloys diffuse from the cathode end of interconnects beyond critical length (Blech length). Based on the experimental findings, an electromigration failure model which considers the incubation time and Al drift time separately has been established. By utilizing the new electromigration test structures and innovative data analysis methods, the model has been experimentally verified. The model predicts that lifetimes of Al-Cu interconnects at W plug contacts/vias under operating conditions are dominated by Cu diffusion (incubation times) in Al-Cu. It has been attempted to apply the established model to the Al filled vias and Cu vias. It has been shown that frequently observed larger standard deviations of electromigration failure distributions from Al filled vias are due to the variation in the electromigration-induced void location. For Cu-doped Al filled vias, the electromigration failure mechanisms is thought to be the same as for Al-Cu interconnects at W plug contacts/vias, which is Cu diffusion dominated.... (author abst.) |
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