Stuffed barrier claims

10/01/1998

Stuffed barrier claims

With regard to Ron Nowicki`s letter in the August issue (p. 18), I think the first use of "stuffed barriers" was described in a 1976 paper (P.H. Holloway, et al., J. Appl. Phys. 47, 3769). Evaporation of an Au layer over the Cr adhesion layer was interrupted, and formation of Cr2O3 in the Au grain boundaries was accomplished by heat treatment in O2 before completion of the Au deposition. One must be especially careful to claim a "first" in anything because of the specialization of fields. Nowicki may have been first to use stuffing for Ti/W, as he claims.

Bill Westwood, THINK Films, ph 613/829-5790; [email protected]

Thank you for your comments. Fundamental principles are applied to many different applications such that "invention" is often difficult to determine. In the case of grain-boundary stuffing to improve thin-film barrier properties, the first principle behind it has been commonly understood for many years. I found a reference to D. Turnbull, "Atom Movements," ASM Seminar, 1951, p. 129, stating that diffusion is more rapid along grain boundaries than in the interiors of crystals. With this understanding, it is a simple intuitive leap (at least in hindsight) to realize that grain boundaries can be stuffed to block diffusion paths. Then, it`s a matter of spending months to create a manufacturable process, before bringing in the IP lawyers.

Ed Korczynski, Sr. Technical Editor