(Color online) Schematic representation of a quarter-spherical void growth mechanism (a) and a semicylindrical growth mechanism (b).
(Color online) Schematic representation of the different phases during the evolution of the semispherical void growth.
(Color online) Simulation of the resistance profile during void growth in a stressed line using a quarter-spherical void growth model.
(Color online) Comparison of the normalized resistance profile of the semicylindrical, semispherical, and the quarter-spherical void-growth model.
Resistance profiles for a typical electromigration experiment with 3-mm-long copper lines and 10/15 nm TaN/Ta barrier (, ). The inset shows a TEM cross section of the tested line.
Resistance profiles of a typical electromigration experiment carried in 1.5-mm-long 100-nm-wide copper lines with 5/10 nm TaN /Ta conformal barrier (, ). The inset shows a TEM cross section of the line. The earliest jump shows a resistance increase.
Post-stress FIB cross section of a tested line. The void displays a larger length than depth.
(Color online) TEM cross section of a void after EM testing. The line cross-sectional area is completely voided.
(Color online) Simulation of the effect of the barrier thickness on the size of the resistance jump and on the slope of the resistance increase.
Experimental 5/10 nm TaN/Ta nonconformal barrier, 1.5-mm-long, 100-nm-wide copper lines. The inset shows a TEM cross section of the line (, ). The earliest jump shows a resistance increase.
(Color online) Simulation of the effect of the line length in the size of the jump and in the increase of resistance.
(Color online) Simulation of the effect of the Cu line width on the size of the resistance jump and on the increase of resistance.
(Color online) Example of a typical experimental resistance profile. Resistance jumps are indicated with arrows. Bottom frame: schematic of the state of the line at several slots of time.
Resistance profile, obtained upon electromigration stressing (, ), and simulation profile, applying the semicylindrical model, of 1.5-mm-long copper lines with a 5/10 nm TaN/Ta nonconformal barrier. Physical failure analysis reveals two voids (upper frame), corresponding to the two “jumps” in the resistance profile. The physical size of the voids agrees with the simulated size. Combined voiding of the line results in an increase of the slope after the second jump. The inset shows a TEM cross section of a typical line.
(Color online) Effect of different void aspect ratios, described with the model parameter IR.
Multiple linear regression analysis of 3 mm copper lines.
Simulation results and fitting parameters from the semicylindrical model application.
Semicylindrical simulation parameters.
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