Reliability test structure for multilevel interconnect
View Patent ↗Embodiments in accordance with the present invention relate to structures and methods allowing stress-induced electromigration to be tested in multiple interconnect metallization layers. An embodiment of a testing structure in accordance with the present invention comprises at least two segments of a different metal layer through via structures. Each segment includes nodes configured to receive force and sense voltages. Selective application of force and sense voltages to these nodes allows rapid and precise detection of stress-induced immigration in each of the metal layers.
1. An electromigration test method comprising:
disposing a test structure on a substrate, the test structure comprising,
a first metallization layer having a first portion and a second portion, and
a second metallization layer having a first portion and a second portion,
a dielectric layer between the first and second metallization layers,
a first electrically conducting via extending through the dielectric layer and in direct contact with the first portion of the first metallization layer and with the first portion of the second metallization layer,
a second electrically conducting via extending through the dielectric layer and in direct contact with the first portion of the second metallization layer and with the second portion of the first metallization layer,
a third electrically conducting via extending through the dielectric layer and in direct contact with the second portion of the first metallization layer and with the second portion of the second metallization layer;
applying a force voltage to one of the first and second portions of one of the first and second metallization layers; and
detecting a changed sense voltage over time at another of the one of the first and second portions of one of the first and second metallization layers, wherein the changed sense voltage reveals a location of electromigration in at least one of the first and second metallization layers.
2. The electromigration test method of claim 1 further comprising:
applying a second force voltage to a different one of the first and second portions of the one of the first and second metallization layers, the different one of the first and second portions of the one of the first and second metallization layers intermediate between a location of application of the force voltage and a location of detection of the changed sense voltage; and
detecting a second changed sense voltage to locate a position of the electromigration in the test structure.
3. The electromigration test method of claim 1 wherein the force voltage is applied to a force node exposed by a scribe line, and the sense voltage is detected on a sense node exposed by the scribe line.
4. The electromigration test method of claim 1 further comprising changing a temperature of the substrate prior to or during application of the force voltage.
5. The electromigration test method of claim 1 wherein each of the first and second portions of the first metallization layer comprises a force node and a sense node.
6. The electromigration test method of claim 5 wherein the force and sense nodes of the first metallization layer extend to a scribe line.
7. The electromigration test method of claim 5 wherein the sense node is disposed between the force node and the electrically conducting via connecting the first and second metallization layers.
8. The electromigration test method of claim 1 wherein each of the first and second portions of the second metallization layer comprises a force node and a sense node.
9. The electromigration test method of claim 8 wherein the force and sense nodes of the second metallization layer extend to a scribe line.
10. The electromigration test method of claim 8 wherein the sense node is disposed between the force node and the electrically conducting via.
11. The electromigration test method of claim 8 wherein the sense node is disposed between the force node and the electrically conducting via connecting the first and second metallization layers.
12. The electromigration test method of claim 1 wherein the first metallization layer underlies the second metallization layer.
13. The electromigration test method of claim 1 wherein the second metallization layer underlies the first metallization layer.
14. The electromigration test method of claim 1 wherein the first and second metallization layers form successive metallization layers of the test structure.
15. The electromigration test method of claim 1 wherein at least one of the first and second metallization layers comprises copper.
16. The electromigration test method of claim 1 wherein one of the first, second, and third electrically conducting vias comprises tungsten.
17. The electromigration test method of claim 1 wherein the first and second portions of the first metallization layer have a length of about 200 microns or greater.
18. The electromigration test method of claim 1 wherein the first and second portions of the second metallization layer have a length of about 200 microns or greater.
19. The electromigration test method of claim 1 further comprising forming on a scribe line of the substrate, a force node and a sense node of the first portion of the first metallization layer, a force node and a sense node of the second portion of the first metallization layer, a force node and a sense node of the first portion of the second metallization layer, and a force node and a sense node of the second portion of the second metallization layer.