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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Aluminum hollow stn ユcmre is adopted to railway carbodies to improve specific st三 ffness ， but the acoustic transmission loss property of the hollow struc 【 ure has not been examined in detail ， We study the transrnission loss with numerical analysis techn 孟 que， and find out thanhe transmission loss is worse than the single plate with equivalent mass auhe frequency ， at which the l st vibration mode of each plate element separated by rib is excited ． This phenomenon occurs 忙 o arbitrary cross section structure with rib ， therefore it is not easy to simuhaneously 油 prove the specific sIiffness and the acoustic transmission loss property ． We 盒nd tha丗 ｝ e numerical analysis resuh coincides with experiment data very welL