The electromigration lifetime is measured for a large number of copper lines encapsulated in an organosilicate glass low-permittivity dielectric. Three testing variables are used: the line length, the electric current density, and the temperature. A copper line fails if a void near the upstream via grows to a critical volume that blocks the electric current. The critical volume varies from line to line, depending on line-end designs and chance variations in the microstructure. However, the statistical distribution of the critical volume (DCV) is expected to be independent of the testing variables. By contrast, the distribution of the lifetime (DLT) strongly depends on the testing variables. For a void to grow a substantial volume, the diffusion process averages over many grains along the line. Consequently, the void volume as a function of time, V(t), is insensitive to chance variations in the microstructure. As a simplification, we assume that the function V(t) is deterministic, and calculate this function using a transient model. We use the function V(t) to convert the experimentally measured DLT to the DCV. The same DCV predicts the DLT under untested conditions.
In this work, we explain how the manufacturing technology and reliability for advanced interconnects is impacted by the choice of metallization and interlayer dielectric (ILD) materials. The replacement of aluminum alloys by copper, as the metal of choice at the 130nm technology node, mandated notable changes in integration, metallization, and patterning technologies. Those changes directly impacted the reliability performance of the interconnect system. Although further improvement in interconnect performance is being pursued through utilizing progressively lower dielectric constant (low-k) ILD materials from one technology node to another, the inherent weak mechanical strength of low-k ILDs and the potential for degradation in the dielectric constant during processing, pose serious challenges to the implementation of such materials in high volume manufacturing. We will consider the cases of two ILD materials; carbon-doped silicon dioxide (CDO) and low-k spin-on-polymer to illustrate the impact of ILD choice on the process technology and reliability of copper interconnects. preprint pdf 2.49 MB
The electromigration lifetime is measured for a large number of copper lines encapsulated in an organosilicate glass low-permittivity dielectric. Three testing variables are used: the line length, the electric current density, and the temperature. A copper line fails if a void near the upstream via grows to a critical volume that blocks the electric current. The critical volume varies from line to line, depending on line-end designs and chance variations in the microstructure. However, the statistical distribution of the critical volume (DCV) is expected to be independent of the testing variables. By contrast, the distribution of the lifetime (DLT) strongly depends on the testing variables. For a void to grow a substantial volume, the diffusion process averages over many grains along the line. Consequently, the void volume as a function of time, V(t), is insensitive to chance variations in the microstructure. As a simplification, we assume that the function V(t) is deterministic, and calculate this function using a transient model. We use the function V(t) to convert the experimentally measured DLT to the DCV. The same DCV predicts the DLT under untested conditions.
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