Anomalous behavior of resistance in Al alloy interconnections stacked with Ti layers during electromigration tests

Kouno, T.; Hosaka, Mariko; Niwa, H.; Yamada, M.

doi:10.1116/1.589528

Cited by 5 publications

(5 citation statements)

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“…The mechanism responsible for this phenomenon is not clear, but it resembles the known effect of the extra Al growth between anti-reflection coated ͑ARC͒ TiN and Al 3 Ti during EM tests. 2 Some Si precipitates can be seen in the single-level interconnections shown in Fig. 12.…”

Section: E Precipitatesmentioning

confidence: 96%

“…The decreased resistance in EM tests was thought to be a result of the observed Al thickening in the line. 1,2 The Al atoms needed for the Al thickening were thought to be supplied from the cathode pad, although the mechanism responsible for the Al thickening could not be determined clearly. Since the Al supplied from the cathode pad causes not just Al thickening but also suppression of void growth, it is difficult to estimate the EM lifetime of these interconnections using the conventional single-level test structure.…”

Section: Introductionmentioning

confidence: 99%

“…5 Also the longer EM lifetime was explained by making the assumption that Al 3 Ti, formed by a reaction between Al and Ti, could act as an alternative current pass 3 or by assuming that the migration of Al atoms could be suppressed at the Al 3 Ti/Al interface. 4 On the other hand, it was recently found that the line resistance of the single-level Al alloy interconnections stacked with Ti during EM acceleration tests monotonically decreased until it rapidly increased and the line failed, [1][2][3] and the rate of the resistance decrease increased by increasing the linewidth. 2 It was also found that the Al alloy layer thickened locally near the anode end 1 or uniformly between the anode end and the cathode one 2 for lines with decreased resistance.…”

Section: Introductionmentioning

confidence: 99%

“…4 On the other hand, it was recently found that the line resistance of the single-level Al alloy interconnections stacked with Ti during EM acceleration tests monotonically decreased until it rapidly increased and the line failed, [1][2][3] and the rate of the resistance decrease increased by increasing the linewidth. 2 It was also found that the Al alloy layer thickened locally near the anode end 1 or uniformly between the anode end and the cathode one 2 for lines with decreased resistance. The decreased resistance in EM tests was thought to be a result of the observed Al thickening in the line.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5] Low via resistance in interconnections stacked with Ti was explained by the protection of the Al surface during TiN sputtering against nitrogen diffusion. 5 Also the longer EM lifetime was explained by making the assumption that Al 3 Ti, formed by a reaction between Al and Ti, could act as an alternative current pass 3 or by assuming that the migration of Al atoms could be suppressed at the Al 3 Ti/Al interface.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Al3Ti intermetallic compound on electromigration lifetime of Al alloy interconnections

Kouno

Hosaka

Niwa

et al. 1998

Journal of Applied Physics

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The dependence of the electromigration (EM) lifetime and the cross-sectional structure of interconnections after EM tests on linewidths was investigated in multi-level and single-level Al alloy interconnections consisting of a top–TiN/Ti/Al–0.5%Cu/TiN/Ti–bottom stack. In this study, an almost uniform Al3Ti intermetallic compound layer was formed by a well-known reaction between the Ti and Al. We found the following anomalous behavior: the mean time to failure (MTF) of EM in the multi-level interconnections with tungsten diffusion barriers decreased by increasing the linewidth. We also found that in the multi-level interconnections after EM tests, independent of linewidths, a local Al thickening formed near the anode end of the line and voids formed near the cathode end. On the other hand, in the single-level interconnections with bonding pads, the MTF of EM increased by increasing the linewidth and, after EM tests, a local Al thickening formed near the anode end even though no voids were observed near the cathode end. This directly opposed EM lifetime dependency on linewidth found in the multi-level and single-level interconnections and the observed Al thickening correlate closely with the fast diffusitivity of Al atoms at the interface between the Al3Ti and Al and/or between the Al3Ti and TiN.

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Section: E Precipitatesmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%