Texas Instruments Corporation

Nancy R Ota

Daniel Joseph Stillman

Cheryl Diane Hartfield

One embodiment of the invention is a method for evaluating a material such as low-k dielectric, by a stress-generating test tool such as a needle. The evaluation object is shaped as a stack of adhering layers: low-k dielectric, first metal (preferably copper), barrier metal (preferably tantalum nitride), and second metal (preferably aluminum). A numerical correlation is established between a cracking in the barrier metal layer caused by probing and a damage in the layer of insulating material-to-be-tested. A predetermined number of locations of the top metal layer is selected for the probing step comprising touch-down, applying force, and lifting is repeated so that the number of repeats provide a pre-determined statistical confidence level. The top metal layer is then removed by a chemical etch solution so that the etch solution also penetrates into any stress-created cracks of the barrier metal layer underneath the imprints, and further dissolves a portion of the first metal layer, generating cavities in the first metal layer. The occurrence of all first metal cavities is recorded and correlated with the probing.

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Keller, TX, United States of America

Nancy R Ota