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Stereological analysis has been coupled with transmission electron microscope (TEM) orientation mapping to investigate the grain boundary character distribution in nanocrystalline copper thin films. The use of the nanosized (

In this paper, a recently developed high resolution electron diffraction technique is employed to characterize the grain orientation and grain boundaries for 45 nm node Cu interconnects with SiCN capping. The results are applied to evaluate the grain structure effect on electromigration (EM) reliability. We first calculate the flux divergence for void formation using interfacial and grain boundary diffusivities extracted from the resistance evolution of test structures observed during EM tests. To further correlate grain structure statistics with EM failure statistics, the EM lifetime distribution for Cu interconnects with CoWP capping is analyzed using a microstructure-based statistical model.

A recently developed precession electron diffraction (PED) technique in transmission electron microscopy (TEM) was employed to characterize the grain orientation and grain boundaries for Cu interconnects of the 45 nm node. The results showed a strong

A combination of diffraction scanning transmission electron microscopy (D-STEM) and automated precession microscopy is used to obtain orientation information from 108 copper grains in 120 nm wide copper interconnect lines. Grain boundary analysis based on this orientation data reveals that Σ3n (n = 1, 2) boundaries are predominant in these lines. Finite element analysis reveals regions of high and low stresses within the copper microstructure.

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

The relative contributions of various defects to the measured resistivity in nanocrystalline Cu were investigated, including a quantitative account of twin-boundary scattering. It has been difficult to quantitatively assess the impact twin boundary scattering has on the classical size effect of electrical resistivity, due to limitations in characterizing twin boundaries in nanocrystalline Cu. In this study, crystal orientation maps of nanocrystalline Cu films were obtained via precession-assisted electron diffraction in the transmission electron microscope. These orientation images were used to characterize grain boundaries and to measure the average grain size of a microstructure, with and without considering twin boundaries. The results of these studies indicate that the contribution from grain-boundary scattering is the dominant factor (as compared to surface scattering) leading to enhanced resistivity. The resistivity data can be well-described by the combined Fuchs–Sondheimer surface scattering model and Mayadas–Shatzkes grain-boundary scattering model using Matthiessen's rule with a surface specularity coefficient of p = 0.48 and a grain-boundary reflection coefficient of R = 0.26.

In this work, a recently developed electron diffraction technique called diffraction scanning transmission electron microscopy (D-STEM) is coupled with precession electron microscopy to obtain quantitative local texture information in damascene copper interconnects (1.8µm‐70 nm in width) with a spatial resolution of less than 5 nm. Misorientation and trace analysis is performed to investigate the grain boundary distribution in these lines. The results reveal strong variations in texture and grain boundary distribution of the copper lines upon downscaling. Lines of width 1.8µm exhibit a strong!111"normal texture and comprise large micron-size grains. Upon downscaling to 180 nm, a{111}!110"bi-axial texture has been observed. In contrast, narrower lines of widths 120 and 70 nm reveal sidewall growth of{111} grains and a dominant!110"normal texture. The microstructure in these lines comprises clusters of small grains separated by high angle boundaries in the vicinity of large grains. The fraction of coherent twin boundaries also reduces with decreasing line width. (Some figures may appear in colour only in the online journal)