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Solute Addition to Increase Electromigration Lifetime in Aluminum

IP.com Disclosure Number: IPCOM000073819D
Original Publication Date: 1971-Feb-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Freedman, JF: AUTHOR [+2]

Abstract

The addition of small amounts of nickel to aluminum will significantly enhance the electromigration lifetime. Nickel has a small solubility in the aluminum lattice. This is based on the fact that the heat of solution is extremely large. One of the reasons for the high of solution is the large heat of formation of the aluminum-nickel intermetallic.

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Solute Addition to Increase Electromigration Lifetime in Aluminum

The addition of small amounts of nickel to aluminum will significantly enhance the electromigration lifetime. Nickel has a small solubility in the aluminum lattice. This is based on the fact that the heat of solution is extremely large. One of the reasons for the high of solution is the large heat of formation of the aluminum-nickel intermetallic.

Two sets of aluminum film samples were prepared using radio frequency (RF) heating, 10-/7/ Torr pressure and substrate temperature of approximately 200 degrees C. The films were made in three successive depositions: aluminum-nickel-aluminum, in one pump down. Total thickness was 5000 omicron A in both cases.

The first sample was analyzed to contain 1% nickel. After annealing for homogenization at 560 degrees C. for 20 minutes, (R (room temp.)/ /R/ liquid helium (resistance ratio) = 7.4) it exhibited a lifetime of 45 hours at 175 degrees
C., and 4 x 10/6/ amp/cm/2/ , compared to 1-3 hours for control (pure aluminum). The second sample (R(room temperature)/R liquid helium = 8.0) exhibited a lifetime of 100-300 hours at 2 x 10 amp/cm and 175 degrees C., compared to 30 hours for the control samples. The improvement of about 10 times was obtained using nickel as a dopant.

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