Ultrathin cobalt-alloyed barrier layers for copper metallization by a new seeding and electroless-deposition process

Abstract Pioneering activation-seeding processes grow catalytic particles with sizes exceeding 10 nm due to agglomeration, and thus are unable to act as a template for electroless deposition of a barrier layer with a thickness of 10 nm or less, which is desperately needed for the incoming ULSI copper interconnecting technology. In this work, the capacity of a seeding process to grow a continuous Co-P barrier layer of 8-nm thickness on thermally oxidized SiO 2 layers using electroless deposition will be demonstrated. The Co-P barrier layer works effectively in retarding (a) Cu agglomeration and (b) Cu diffusion into the dielectric layer subjected to thermal annealing. Evidently, thermal stability of the Cu film on SiO 2 is markedly strengthened by interposing the 8-nm-thick barrier layer. The mechanism of the interposed barrier layer in enhancing thermal stability of the metallization layer is currently under investigation.