Method for measuring electromigration-induced resistance changes
First Claim
1. A method for determining resistance changes induced by electromigration in a conductive pattern, comprising at least one sequence of the steps of:
- applying substantially simultaneous a first unidirectional current to a first conductive pattern and a second alternating symmetric current to a second conductive pattern, said first and said second conductive pattern being essentially identical and placed on the same substrate, said first current and said second current thereby leading to substantially the same amount of power dissipation in said first conductive structure and said second conductive structure respectively;
measuring the resistance changes of said first conductive pattern and said second conductive pattern by applying substantially simultaneous a third alternating current to said first conductive pattern and a fourth alternating current to said second conductive pattern, said third current and said fourth current thereby leading to substantially the same amount of power dissipation in said first conductive structure and said second conductive structure respectively.
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Abstract
A method for measuring resistance changes is described to study electromigration induced failures in conductive patterns. This method can provide a basis for lifetime predictions based on low value failure criteria, i.e. small resistance changes in the conductive patterns in a limited period of time. Two essentially identical so-called test and reference structures are placed close to each other on the same substrate and submitted to at least one sequence of a stress period and a measurement period. During a stress period, a DC current with a high current density is applied to the test structure thereby enhancing electromigration, while substantially simultaneous an AC current is applied to the reference structure leading to the same amount of power dissipation in said reference structure as the amount of power dissipation in said test structure, introduced by said DC stress current. The method of the present invention makes it possible to distinguish in a very accurate way between resistance changes induced by electromigration and resistance changes induced by other disturbances.
14 Citations
10 Claims
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1. A method for determining resistance changes induced by electromigration in a conductive pattern, comprising at least one sequence of the steps of:
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applying substantially simultaneous a first unidirectional current to a first conductive pattern and a second alternating symmetric current to a second conductive pattern, said first and said second conductive pattern being essentially identical and placed on the same substrate, said first current and said second current thereby leading to substantially the same amount of power dissipation in said first conductive structure and said second conductive structure respectively; measuring the resistance changes of said first conductive pattern and said second conductive pattern by applying substantially simultaneous a third alternating current to said first conductive pattern and a fourth alternating current to said second conductive pattern, said third current and said fourth current thereby leading to substantially the same amount of power dissipation in said first conductive structure and said second conductive structure respectively. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification