Strain-Induced Grain Growth during Rapid Thermal Cycling of Aluminum Interconnects (original) (raw)
Related papers
MRS Proceedings, 2002
Electromigration during accelerated testing can induce large scale plastic deformation in Al interconnect lines as recently revealed by the white beam scanning X-ray microdiffraction. In the present paper, we provide a first quantitative analysis of the dislocation structure generated in individual micron-sized Al grains during an in-situ electromigration experiment. Laue reflections from individual interconnect grains show pronounced streaking after electric current flow. We demonstrate that the evolution of the dislocation structure during electromigration is highly inhomogeneous and results in the formation of unpaired randomly distributed dislocations as well as geometrically necessary dislocation boundaries. Approximately half of all unpaired dislocations are grouped within the walls. The misorientation created by each boundary and density of unpaired individual dislocations is determined.
Lawrence Berkeley National Laboratory, 2003
Electromigration during accelerated testing can induce large scale plastic deformation in Al interconnect lines as recently revealed by the white beam scanning X-ray microdiffraction. In the present paper, we provide a first quantitative analysis of the dislocation structure generated in individual micron-sized Al grains during an in-situ electromigration experiment. Laue reflections from individual interconnect grains show pronounced streaking after electric current flow. We demonstrate that the evolution of the dislocation structure during electromigration is highly inhomogeneous and results in the formation of unpaired randomly distributed dislocations as well as geometrically necessary dislocation boundaries. Approximately half of all unpaired dislocations are grouped within the walls. The misorientation created by each boundary and density of unpaired individual dislocations is determined.
Defect behavior in aluminum interconnect lines deformed thermomechanically by cyclic joule heating
Acta Materialia, 2008
Al-1wt.% Si lines were deformed thermomechanically by cyclic joule heating induced by applying an AC current. Scanning electron microscopy revealed arrays of wavelike surface intrusions/extrusions aligned along low-index crystallographic directions after a few thousand thermal cycles. Transmission electron microscopy observations of cross-sections of selected regions shows that in grains that developed intrusions/extrusions, dislocations nucleated at the film-substrate interface, glided to the surface, and escaped. The densities of dislocations and prismatic loops observed here are similar to those observed in mechanical fatigue experiments on bulk aluminum.
New synchrotron x-ray microbeam methodology is used to analyze and test the reliability of interconnects. The early stage of plastic deformation induced by electromigration before any damages become visible has been recently revealed by white beam scanning X-ray microdiffraction during an accelerated test on Al interconnect lines. In the present paper, we provide a quantitative analysis of the dislocation structure generated in several micron-sized Al grains in both the middle region and ends of the interconnect line during an in-situ electromigration experiment. We demonstrate that the evolution of the dislocation structure during electromigration is highly inhomogeneous and results in the formation of randomly distributed geometrically necessary dislocations as well as geometrically necessary boundaries. The orientation of the activated slip systems and rotation axis depends on the position of the grain in the interconnect line. The origin of the observed plastic deformation is considered in view of constraints for dislocation arrangements under applied electric field during electromigration. The coupling between plastic deformation and precipitation in the Al (0.5% wt. Cu) is observed for the grains close to the anode/cathode end of the line.
MATERIALS RESEARCH SOCIETY …, 2000
In situ transmission electron microscopy (150 kV) has been employed to study the evolution of dislocation microstructure during relatively rapid thermal cycling of a 200 nm Al thin film on Si substrate. After a few thermal cycles between 150 and 500C, nearly stable Al columnar grain structure is established with average grain less than a micron. On rapid cooling (3–30+ C/s) from 500C, dislocations first appear at a nominal temperature of 360-380C, quickly multiplying and forming planar glide plane arrays on further cooling. From a large number of such experiments we have attempted to deduce the dislocation evolution during thermal cycling in these polycrystalline Al films and to account qualitatively for the results on a simple dislocation model.
Journal of Applied Physics, 2008
We report here an in-depth synchrotron radiation based white beam x-ray microdiffraction study of plasticity in individual grains of an Al ͑Cu͒ interconnect during the early stage of electromigration ͑EM͒. The study shows a rearrangement of the geometrically necessary dislocations ͑GNDs͒ in bamboo typed grains during that stage. We find that about 90% of the GNDs are oriented so that their line direction is the closest to the current flow direction. In nonbamboo typed grains, the Laue peak positions shift, indicating that the grains rotate. An analysis in terms of force directions has been carried out and is consistent with observed EM induced grain rotation and bending.
Journal of Applied Physics, 2003
Electromigration during accelerated testing can induce plastic deformation in apparently undamaged Al interconnect lines as recently revealed by white beam scanning x-ray microdiffraction. In the present article, we provide a first quantitative analysis of the dislocation structure generated in individual micron-sized Al grains during an in situ electromigration experiment. Laue reflections from individual interconnect grains show pronounced streaking during the early stages of electromigration. We demonstrate that the evolution of the dislocation structure during electromigration is highly inhomogeneous and results in the formation of unpaired randomly distributed dislocations as well as geometrically necessary dislocation boundaries. Approximately half of all unpaired dislocations are grouped within the walls. The misorientation created by each boundary and density of unpaired individual dislocations is determined. The origin of the observed plastic deformation is considered in view of the constraints for dislocation arrangements under the applied electric field during electromigration.
Simulations of Dislocation Dynamics in Aluminum Interconnects
MRS Proceedings, 2002
A discrete dislocation simulation of plastic deformation in metallic interconnects caused by thermal stress is carried out. The calculations are carried out using a two dimensional plane strain formulation with only edge dislocations. A boundary value problem is formulated and solved for the evolution of the thermal stress field and the evolution of the dislocation structure in the cross-section of the line as cooling proceeds. For lines with a small cross section (height or width less than 1 μm), the local concentration of stresses due to dislocation patterning strongly affects the overall stress build up and relaxation. The results show a clear dependence of the transverse stress development on the line aspect ratio.