THE METALLURGICAL CONTROL OF ELECTROMIGRATION FAILURE IN NARROW CONDUCTING LINES

Electromigration is a serious potential source of failure in the narro w, thin-film Al-Cu conductors used in modern microelectronic devices. The problem has become more acute as line widths have shrunk to below one micrometer, creating lines with quasi-bamboo microstructures. The usual mechanism of internal electromigration failure in such lines inv olves the formation of a transgranular void across a bamboo grain at t he upstream end of a long, polygranular segment, preceded by the deple tion of copper from both the polygranular segment and the upstream bam boo grain. At least three metallurgical mechanisms are available to in hibit this failure mechanisms and available to inhibit this failure me chanism and improve the useful lifetime of the line. Each of these met hods has been demonstrated in the laboratory environment.