Microstructure control of Al-Cu films for improved electromigration resistance
First Claim
1. A process for producing a thin layer conductive aluminum film having reduced electromigration failures, comprising:
- depositing an aluminum-copper alloy thin film on a substrate;
heating said thin film to a first temperature and maintaining said film at said first temperature for a first length of time; and
heating said thin film to a second temperature, said second temperature being lower than said first temperature, and maintaining said thin film at said second temperature for a second time period sufficient for copper enrichment to occur at grain boundaries of said thin film.
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Accused Products
Abstract
A process for the forming of Al-Cu conductive thin films with reduced electromigration failures is useful, for example, in the metallization of integrated circuits. An improved formation process includes the heat treatment or annealing of the thin film conductor at a temperature within the range of from 200° C. to 300° C. for a time period between 10 minutes and 24 hours under a reducing atmosphere such as 15% H2 in N2 by volume. Al-Cu thin films annealed in the single phase region of a phase diagram, to temperatures between 200° C. and 300° C. have θ-phase Al2 Cu precipitates at the grain boundaries continuously become enriched in copper, due, it is theorized, to the formation of a thin coating of θ-phase precipitate at the grain boundary. Electromigration behavior of the aluminum is, thus, improved because the θ-phase precipitates with copper hinder aluminum diffusion along the grain boundaries. Electromigration, then, occurs mainly within the aluminum grains, a much slower process.
24 Citations
18 Claims
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1. A process for producing a thin layer conductive aluminum film having reduced electromigration failures, comprising:
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depositing an aluminum-copper alloy thin film on a substrate; heating said thin film to a first temperature and maintaining said film at said first temperature for a first length of time; and heating said thin film to a second temperature, said second temperature being lower than said first temperature, and maintaining said thin film at said second temperature for a second time period sufficient for copper enrichment to occur at grain boundaries of said thin film. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 16, 17, 18)
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12. In a process for forming conductive films on a substrate in the manufacture of integrated circuit computer chips wherein an aluminum-copper alloy film is deposited on said substrate, the improvement comprising:
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heating said thin film to a sufficient temperature and for a sufficient length of time for forming a substantially continuous, coherent copper precipitate along the grain boundaries of the deposited film; and cooling said thin film to a lower temperature. - View Dependent Claims (13, 14)
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15. A process for producing thin layer conductive films having reduced electromigration failures comprising:
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sputter depositing an aluminum-copper alloy thin film having about 2 percent copper in aluminum by weight on a substrate at about room temperature; performing a first heat treatment of said thin film, said treatment comprising; heating said thin film to a first temperature above the solvus temperature of said film; maintaining said thin film at said first temperature for a first time period; and cooling said thin film to about room temperature; and performing a second heat treatment of said thin film, said treatment comprising; heating said thin film to a second temperature less than the solvus temperature of said film; maintaining said thin film at said second temperature for a time period sufficient for copper enrichment to occur at aluminum grain boundaries; and cooling said thin film to about room temperature.
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Specification