Reliability of porous low-k dielectrics under dynamic voltage stressing

We investigate porous low-k SiCOH under dynamic voltage stress to provide new insights into electrical breakdown. Our results are consistent with the existence of two breakdown mechanisms: the first is independent of trench barrier material and other processing details and is identical for DC, unipolar and high frequency bipolar (AC) stress. This mechanism appears to involve permanent physical damage to the dielectric. The second breakdown mechanism is dependent upon process conditions, and is evident only during low frequency bipolar stress. We discuss our findings in terms of breakdown due to the presence of Cu in the dielectric, charge trapping and bond breakage.