The relationship between TiN microstructures and diffusion barrier properties of TiN against Cu was investigated. TiN deposited by a chemical vapor deposition (CVD) method is composed of columnar grains grown normal to the sidewall on the side of the trench. On the other hand, the gram boundaries of sputter-deposited TiN tilt upward from the normal direction to the sidewall, and the tilt angle depends on the sputtering conditions. Voids between TiN grains are observed on the side of the trench and the size of the voids depends on the deposition conditions. In the Cu/CVD-TiN (the upper/lower layer) and Cu/conventional sputtered TiN system, no Cu is detected in surrounding SiO, films, either outside the sidewall or underneath the bottom of the trench after annealing at 400°C for 3 mm. However, in the Cu/long-throw sputtered TiN system, where TiN is composed of columnar grains with void regions between grains, and the tilt angle of the grain boundaries from the normal direction to the sidewall is 27°, some Cu is detected outside the sidewall, even when the TiN thickness on the side of the trench is equal to or thicker than that of CVD-TiN or conventionally sputtered TiN. The diffusion barrier property of TiN in Cu metallization depends on the TiN grain structures rather than on the TiN thickness on the side of the trench. InfroductionCu has been considered as a promising metallization

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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Stress migration ͑SM͒ behavior in Cu damascene interconnects was investigated in detail using different kinds of test patterns. SM failure was found in narrow lines that are very long, or connecting to a wide line. In the pattern in which narrow lines are connected to wide metal, the failure rate decreased as the narrow metal becomes longer. It was found that the failure rate in minimum 0.14 m wide lines is more than that in 0.2-0.42 m wide lines. The result of the test patterns with different via arrangements clarified that the placing of the vias at the edge of the M1 line plays an important role in the SM phenomenon in narrow copper lines. Failure analysis using scanning transmission electron microscopy revealed voiding beneath the via at the failure points for all test patterns. It is shown that the enhanced failure rate in the minimum wide lines and the via arrangement effect cannot be understood by the previous diffusion mechanism. Based on these results, the effect of the via arrangement close to the edge of the lower lines on SM failure in narrow lines is discussed.

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