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Metallurgical Scheme for an Electromigration Resistant, High Conductivity, Extrusion Resistant Conductor

IP.com Disclosure Number: IPCOM000046218D
Original Publication Date: 1983-Jun-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Lloyd, JR: AUTHOR [+3]

Abstract

The solution to the problems of electromigration performance, resistance to electromigration or thermal stress-induced extrusions and provision of high conductivity requires a metal with properties which are usually incompatible. For example, high conductivity usually implies low mechanical strength. However, these properties can be combined without too much compromise by utilizing a high conductivity matrix metal, such as copper or silver, with a dispersion of an insoluble metal, such as chromium.

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Metallurgical Scheme for an Electromigration Resistant, High Conductivity, Extrusion Resistant Conductor

The solution to the problems of electromigration performance, resistance to electromigration or thermal stress-induced extrusions and provision of high conductivity requires a metal with properties which are usually incompatible. For example, high conductivity usually implies low mechanical strength. However, these properties can be combined without too much compromise by utilizing a high conductivity matrix metal, such as copper or silver, with a dispersion of an insoluble metal, such as chromium.

The chromium is used for its well-known properties of adhesion improvement and as an effective diffusion barrier. For this chromium, underlayers and top covers over the copper or silver are required. The process, however, does not strengthen the conductor metal and, especially in the case of silver, extrusions are readily formed due to an electromigration-induced stress while under high current use.

To reduce the propensity for extrusion, a fine dispersion of chromium such as about l% or less in total volume, is incorporated in the copper or silver conductor. Chromium has a vanishingly small solubility in silver or copper; thus the chromium will exist primarily as small chromium particles with very little dissolved in the lattice. Thus, the conductor resistivity will not be sacrificed unduly, but the strength of the metal in the conductor will be enhanced. Therefore...