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The distribution of breakdown times of thin film dielectrics, stressed in a constant voltage mode, is generally interpreted in terms of percolation theory of dielectric breakdown. The percolation model suggests that relative distribution of failure times (normalized to the mean) should narrow down considerably for thicker dielectrics. Explicitly contradicting this prediction, we find a larger distribution of failure times even for relatively thick polycrystalline oxides. We use atomic force microscopy and conductive AFM measurements to confirm that breakdown in these films are primarily localized in the grain boundaries, decorated with large number of pre-existing defects. The classical percolation model—adapted to this specific situation of spatially localized trap generation—offers an intuitive explanation of the breadth of the failure time distribution in thick polycrystalline dielectric. The theory offers an opportunity to optimize the intrinsic trade-off between variability and reliability in polycry...

Local strains in the channel and source/drain (S/D) of an advanced complementary metal-oxide-semiconductor device were measured by the geometric phase analysis applied to high resolution transmission electron microscope images. Two-dimensional strain maps were reconstructed for a 45nm p-type metal-oxide-semiconductor device which was strain-engineered using a recessed Si0.82Ge0.18 S/D. Lateral strains were uniform across the channel but vertical strains were found to vary considerably in the channel. Measured strains were used to estimate stresses and hole mobility enhancements.

Relaxation of strain by a partial dislocation and stacking fault in a strained Si film was characterized using geometric phase analysis of high-resolution transmission electron microscope (HRTEM) images. Movement of a 60° glide dislocation from the free surface to the film-substrate interface created a complex state of strain in the film. HRTEM image analysis was used to produce a quantitative measure of the atomic displacement fields that could be used as input to finite-element simulations of stress distributions and resulting affects on band structures.

Phase profiles within core-shell nanowires composed of intrinsic germanium cores and shells of germanium oxide and/or doped germanium were imaged using electron holography in a transmission electron microscope. Accurate mean inner potentials for germanium and its oxide were determined from phase data obtained from experimental electron holography with knowledge of the thickness profile of the nanowire. Using measured and simulated phase profiles, it was possible to determine the dopant concentration within a shell of doped germanium around an intrinsic germanium core. Measurement of mean inner potentials and dopant levels within semiconductor core-shell nanowires was demonstrated.

The effects of Ta barrier thickness on electromigration reliability of dual-damascene Cu/porous methylsilsesquioxane interconnects were investigated. With decreasing Ta barrier thicknesses, the threshold product of current density and line length (jL)c was found to be reduced due to less structural confinement from thinner barriers. The effect can be accounted for by the effective modulus of the structure except for the 75-A Ta barrier where the (jL)c product is reduced more than expected, probably due to the presence of defects in the barrier. Results from the early failure test structures revealed a bimodal failure distribution for samples with the 75-A and l00-A barriers. Focused ion beam microprobe and transmission electron microscopy observations revealed that the weak-mode early failure was caused by Cu outdiffusion through structural defects in the thin Ta barrier.