Browse Prior Art Database

Improvement of Nickel Films for Diffusion Barrier

IP.com Disclosure Number: IPCOM000085371D
Original Publication Date: 1976-Mar-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Asai, KW: AUTHOR [+3]

Abstract

A procedure has been devised for improving the effectiveness of a nickel film serving as a diffusion barrier between two metals being separated by such nickel film.

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Improvement of Nickel Films for Diffusion Barrier

A procedure has been devised for improving the effectiveness of a nickel film serving as a diffusion barrier between two metals being separated by such nickel film.

In making integrated circuits wherein copper is used as an electrical conductor, the latter is not applied directly to the SiO base that forms the supporting unit or chip for all the electrical circuitry used with the copper. The copper must first be made highly adhesive to the SiO(2), and such adhesion is accomplished by laying down a 200 Angstroms thick film of titanium onto the SiO(2) surface prior to the deposition of a 4 micron layer of copper. However, copper is very susceptible to corrosion so a 4 micron film of gold is used to cover the copper, not only to prevent attack of the copper, but to permit the soldering of additional components and/or electrical leads to the chip.

However, copper and gold readily diffuse into each other. To avoid such unwanted atomic excursions, a 1 micron layer of pure nickel is Anterposed between the copper and gold films. Problems arise when subsequent annealing temperatures in excess of 300 degrees C are used to anneal the finished chip. At such elevated temperatures, it was found that pure nickel does not act as a reliable or faithful diffusion barrier between the gold and copper and the latter's sheet resistance degrades.

To avoid such unwanted diffusion so as to protect the life of the copper conductors, it is...