Origin of

08/01/1998

Origin of "stuffed diffusion barrier"

I enjoyed reading "High-throughput W/Ti barrier sequential deposition" (June, p. 127). It should be noted that the authors failed to cite the prior papers that discussed in depth the method they authored!

For example, the "stuffed barrier" concept was initially introduced by this writer along with nuclear analyses done by Ian Mitchell at Chalk River Nuclear Labs in Canada [re: Nowicki, Harris, M. Nicolet, and Mitchel, Thin Solid Films, Vol. 53, pp.195-205, 1978]. This study was done after significant input from Arthur Learn, who had published an earlier paper on the improvement of electromigration resistance in Al metallization by exposure of layered Al films to oxygen.

Later, the profound effect of oxygen was reported by Baker, Blattner, Nadel, Evans, and Nowicki in Thin Solid Films, Vol. 69, pp. 53-62, 1980. In this paper, it was clearly shown that oxygen was present in the W/Ti films that exhibited improved resistance to grain boundary diffusion between Si and Au. Another article was R. Nowicki, "Comparison of RF sputtered titanium-tungsten/gold with DC magnetron sputtered tunsten/gold on silicon," Solid State Technology, pp. 127-130, June, 1982.

More recently, the method of atmospheric exposure of the W/Ti was reported by this author at the 1986 Workshop, "Tungsten and other refractory metals for VLSI applications," and published that year in the Workshop Proceedings, pp. 333-337, by the Materials Research Society (Ed. E. Broadbent).

Hopefully, this communication will clarify the true origins of this methodology.

Ron Nowicki

Integrated Processing

Sunnyvale, CA

Thank you for taking the time to inform us of your early and important work in developing this technology.

- Ed Korczynski, senior technical editor