Electromigration: Difference between revisions

Revision as of 20:09, 23 April 2004

Revision as of 20:58, 23 April 2004

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== History ==

The phenomenon of electromigration has been known for more than 100 years. The topic became increasingly interesting for the first time in the year [[1966]] when the first integrated circuits became commercially available. James R. Black is pioneer on this field of research. The Black equation which was named after him created the basis for all research in this area. At this time the conductive stripsinterconnects were still about 10 mm wide. Nowadays the conductive stripsthey are only some µm or even nm are in width. Therefore this field of research increasingly gains significance.

== Practical implications of electromigration ==

Electromigration decreases the reliability of ICs. In the worst case it can lead to the total failure of one or several lines and thus to an entirely inoperative circuit.

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Since the reliability of interconnect is not only in the ranges of space travel and the military, but also with civilian applications, like for example the anti-skid system of cars, of great importance, high technological and economic meaning is attached to this effect. With the help of the Black equation the life span of conductive strips in integrated circuits (ICs) leaves itself, which under "stress", i.e. external heating and increased current density, was tested, on the life span under material conditions to extrapolate. Due to the relatively high life span of the conductive strips it would be impossible under material conditions to analyze electrical migration and be at the same time on the conditions of the used technologies for chip production. With increasing miniaturization the probability of failure increases circuits (VLSI/ULSI), maximumintegrated of high and, by EM, because both the power density, and the current density increase. Due also to the increasing employment of copper in place of aluminum as conductive strip material this forschungsgebiet for the chip industry becomes ever more important. Copper as conductive strip material is relatively new, due to the associated difficulties in the technological process, in the chip production. It is however a better leader and not as susceptible to electrical migration as aluminum. Therefore the EM research is with copper conductive strips for the moment still another relatively new area. By a reduction of the structure (scaling) by the factor k the power density increases proportionally to k and the current density rises by k2, whereby the EM is strengthened clearly.

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== Fundamentals ==