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The effect of stress migration on electromigration in dual damascene copper interconnects
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10.1063/1.3531393
/content/aip/journal/jap/109/1/10.1063/1.3531393
http://aip.metastore.ingenta.com/content/aip/journal/jap/109/1/10.1063/1.3531393

Figures

Image of FIG. 1.
FIG. 1.

SM Model for void formation rate as a function of temperature. SM is caused by the interaction between the thermomechanical stress in the interconnect systems and the diffusion of vacancies (Ref. 1). The graph shows that the SM is expected to occur at use condition, however at the EM test condition the SM effect is negligible.

Image of FIG. 2.
FIG. 2.

Schematic diagrams of the (a, c) top view and (b, d) side view of via-chain test structures used for the SM-EM interaction study in (a, b) lower and (c, d) upper metal leads, respectively.

Image of FIG. 3.
FIG. 3.

The temperature rise of lower metal multilink test structure as a function of lower metal current density, heated at . It shows that the temperature rise at EM test condition is only about 0.27 K and thus the possibility of temperature-induced failures during EM testing is very minimal.

Image of FIG. 4.
FIG. 4.

Failure distribution of samples under test compared to EM-test only samples for the study of SM/EM interaction in the lower metal interconnects. ALTs show that failure distribution of failed samples under test has trimodal distribution. The inset shows the resistance trend for each group population.

Image of FIG. 5.
FIG. 5.

Cross section of degraded sample after test from (a) FM-I population, where the void formed directly below the via of the cathode end causing open circuit failure. (b) FM-III population, in which the trench void formed in the Cu metal line (Ref. 16).

Image of FIG. 6.
FIG. 6.

Failure distribution of samples under test compared to EM-test only samples for the study of SM/EM interaction in the upper metal interconnects. The lifetime degradation due to SM effect is . The inset shows the resistance trend for each group population.

Image of FIG. 7.
FIG. 7.

TIVA analysis of one of the degraded samples from test in the top metal of the M2 test structure. The rectangle sign shows the stressed test structure. The bright spots indicate the void location where many voids are detected at the end of each single chain metal line.

Image of FIG. 8.
FIG. 8.

FEA simulation of hydrostatic stress in the lower metal test structure (Ref. 16). The nonuniform tensile stress near the via bottom leads to a prominent stress gradient that drives vacancies toward the via.

Image of FIG. 9.
FIG. 9.

FEA simulation of hydrostatic stress in the upper test structure. The nonuniform tensile stress near the upper metal lead (SM-I) and inside the via (SM-II). The resulting stress gradient may favor vacancies to migrate toward these two different areas during SM test.

Image of FIG. 10.
FIG. 10.

Mechanism of SM and EM interaction–an approach using stress evolution diagram. (a) Assuming symmetrical condition where the amount of vacancies near both ends after SM test are the same. (b) As a result, the metal line become more tensile by almost the same increment ( and ) and the time to reach void nucleation is shorter, , during EM test.

Image of FIG. 11.
FIG. 11.

(a) Assuming the amount of vacancies at the cathode region is limited. (b) As a result, there is no tensile stress developed at the cathode side of metal line after SM test. The time to reach void nucleation is the same, , during EM test.

Tables

Generic image for table
Table I.

Statistical test results for test structure. is the measured median time to failure and is the standard deviation of the natural log of the failure times for each population of samples. The error estimates for and were calculated with 90% two-sided confidence bounds.

Generic image for table
Table II.

Statistical test results for test structure.

Generic image for table
Table III.

Material properties used in our simulation model.

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/content/aip/journal/jap/109/1/10.1063/1.3531393
2011-01-14
2014-04-16
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: The effect of stress migration on electromigration in dual damascene copper interconnects
http://aip.metastore.ingenta.com/content/aip/journal/jap/109/1/10.1063/1.3531393
10.1063/1.3531393
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