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Long Life Aluminum Alloy Thin Film Conductors

IP.com Disclosure Number: IPCOM000077248D
Original Publication Date: 1972-Jun-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

d'Heurle, F: AUTHOR [+3]

Abstract

Lifetime of conductors submitted to electromigration conditions can be enhanced by a factor of about ten, as compared with aluminum films containing about 4 wt% copper, with a rather small sacrifice in conductivity, since the resistivity of the proposed aluminum alloy films is only about ten percent greater than that of aluminum films containing copper.

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Long Life Aluminum Alloy Thin Film Conductors

Lifetime of conductors submitted to electromigration conditions can be enhanced by a factor of about ten, as compared with aluminum films containing about 4 wt% copper, with a rather small sacrifice in conductivity, since the resistivity of the proposed aluminum alloy films is only about ten percent greater than that of aluminum films containing copper.

Aluminum thin-film conductors are known to fail because of electromigration when exposed to the prolonged passage of direct current, either continuous or pulsed. Large increases in lifetimes can be obtained by the addition of several weight percent copper or magnesium. However, in this latter case, the increase in lifetime is obtained at the cost of a considerable increase in film resistivity, which is undesirable, either from the consideration of device design, or because of excessive Joule heating. It has been found that a large improvement in lifetime, over that which is obtained by the addition of 3-6 wt% copper, can be achieved by the use of an alloy containing Cu-4 wts, Ni-2 wt% and Mg-1.5 wt%.

The films were prepared by evaporation technique. prior to and during deposition the vacuum in the bell jar was about 1-3 x 10/-7/torr. The substrates were oxidized silicon wafers and maintained at 200 degrees C, during deposition. The films were deposited in a number of successive evaporations in a single pump-down: Al-Cu-Ni-Al-Mg-Al. After deposition, the films were annealed in nitrogen for thirty minutes at a temperature of 340 degrees C.

The stripes were prepared by usual photoresist techniques and were tested for electr...