Noise and fluctuations in submicrometric Al-Si interconnect lines

Low-frequency noise (LFN) in excess has been observed in the past in metal lines subjected to high current densities. Different types of noise and fluctuations have been identified and are briefly summarized in the first part of this paper. Then, some new experimental results, obtained with Al/Si submicrometric lines, are presented. In particular, it has been possible to identify and separate the contribution of three different sources of noise and, from the analysis of the noise component directly related to electromigration, an activation energy of about 1.4 eV has been obtained. This value clearly indicates that in these samples bulk electromigration is the main cause of the noise generation. Moreover, the consistency between the measured level of noise and the value of some physical quantities, contained in a model previously proposed, has been verified. In the final section of the paper, old and new results are utilized in an attempt to provide a satisfactory answer to some of the most important unsolved questions in this field.