HIGH-RELIABILITY COPPER INTERCONNECTS THROUGH DRY-ETCHING PROCESS

A modified high-temperature dry etching technique, which enables aniso tropic patterning with a high etching selectivity and self-aligned pas sivation of a sidewall of an interconnect simultaneously, has been dev eloped for fabrication of sub-quarter-micron Cu interconnects. Resisti vities of the resulting Cu interconnects are in the range of 1.7 to 2. 2 mu Omega.cm for the linewidth of 0.2-3.0 mu m. As a result of electr omigration (EM) tests, it has been observed that median time to failur e (MTF) of the Cu interconnects depends on their linewidth. This behav ior is considered to be caused by their grain structure, such as a bam boo-type structure for linewidths narrower than 0.3 mu m. In compariso n with a MTF of a conventional Al-1% Si line, these Cu interconnects h ave at least 100 times longer lifetime. Activation energy for EM damag e of the 0.7-mu m-wide line is 0.88 eV.