Both mechanical and electronic properties of electroplated copper films used for interconnections were investigated experimentally considering the change of their micro texture caused by heat treatment. The fracture strain of the film annealed at 400°C increased from about 3% to 15% and their yield stress decreased from about 270 MPa to 90 MPa. In addition, it was found that two different fatigue fracture modes appeared in the film. One was a typical ductile fracture mode and the other was brittle one. When the brittle fracture occurred, a crack propagated along weak or porous grain boundaries which were formed during electroplating. The brittle fracture mode disappeared after the annealing at 300°C. These results clearly indicated that the mechanical properties of electroplated copper thin films vary drastically depending on their micro texture. The electrical reliability of the electroplated copper yjin film interconnections was also investigated. The interconnections used for electromigration tests were made using by a damascene process. An abrupt fracture mode due to local fusion appeared in the as-electroplated interconnections. Since the fracture rate increased almost linearly with the square of the applied current density, this fracture mode was dominated by local Joule heating. It seemed that the local current concentration occurred around the porous grain boundaries. The life of the interconnections was improved drastically after the annealing at 400°C. This was because of the increase of the average grain size and the improvement of the quality of grain boundaries in the annealed interconnections. However, the stress-induced migration occurred in the interconnections annealed at 400°C. This was because of the high tensile residual stress caused by the constraint of the densification of the films during annealing by the surrounding oxide film. Therefore, it is very important to control the crystallographic quality of electroplated copper films for improving the reliability of thin film interconnections. The quality of the grain boundaries can be evaluated by applying an EBSD (Electron Back Scatter Diffraction) analysis. New two experimentally determined parameters are proposed for evaluating the quality of grain boundaries quantitatively. It was confirmed that the crystallographic quality of grain boundaries can be evaluated quantitatively by using the two parameters, and it is possible to estimate both the strength and reliability of the interconnections.
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ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems
July 6–8, 2011
Portland, Oregon, USA
Conference Sponsors:
- Electronic and Photonic Packaging Division
ISBN:
978-0-7918-4462-5
PROCEEDINGS PAPER
Effect of Crystallographic Quality of Grain Boundaries on Both Mechanical and Electrical Properties of Electroplated Copper Thin Film Interconnections
Naokazu Murata,
Naokazu Murata
Tohoku University, Sendai, Miyagi, Japan
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Naoki Saito,
Naoki Saito
Tohoku University, Sendai, Miyagi, Japan
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Kinji Tamakawa,
Kinji Tamakawa
Tohoku University, Sendai, Miyagi, Japan
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Ken Suzuki,
Ken Suzuki
Tohoku University, Sendai, Miyagi, Japan
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Hideo Miura
Hideo Miura
Tohoku University, Sendai, Miyagi, Japan
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Naokazu Murata
Tohoku University, Sendai, Miyagi, Japan
Naoki Saito
Tohoku University, Sendai, Miyagi, Japan
Kinji Tamakawa
Tohoku University, Sendai, Miyagi, Japan
Ken Suzuki
Tohoku University, Sendai, Miyagi, Japan
Hideo Miura
Tohoku University, Sendai, Miyagi, Japan
Paper No:
IPACK2011-52048, pp. 677-684; 8 pages
Published Online:
February 14, 2012
Citation
Murata, N, Saito, N, Tamakawa, K, Suzuki, K, & Miura, H. "Effect of Crystallographic Quality of Grain Boundaries on Both Mechanical and Electrical Properties of Electroplated Copper Thin Film Interconnections." Proceedings of the ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems. ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems, MEMS and NEMS: Volume 2. Portland, Oregon, USA. July 6–8, 2011. pp. 677-684. ASME. https://doi.org/10.1115/IPACK2011-52048
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