Line-Width Dependence of Stress in Passivated Al Lines During Thermal Cycling

ABSTRACTWe have obtained theoretical stress-temperature curves for passivated Al lines undergoing thermal cycling. A finite element plane-strain cross-sectional analysis with a time-dependent constitutive property for Al, based on equations for discreteobstacle controlled plasticity, was performed. The parameters for this Al constitutive relation were obtained by fitting with experimentally obtained stress-temperature curves for Al blanket films on silicon. Theoretical results agree well with the x-ray diffraction experimental data of Besser et al.1 Using a time-dependent property for Al helps match the data better than a time-independent property. Theoretical stress-temperature curves were also obtained for the longitudinal, transverse, and normal stress components in aluminum lines for line-widths ranging from 0.5 to 10 µm. The hysteresis of the stress-temperature curve of Al gets less as the line-width gets smaller. All stress components in the Al line change substantially with linewidth for the same oxide thickness.</jats:p

Controlled nucleation of dislocations by a spatially localized stress field

We analyze the nucleation of dislocations in silicon at spatially localized stress fields generated by silicon nitride pads having a high intrinsic stress. The nucleation and final configuration of the dislocations were studied using hot-stage transmission electron microscopy and were compared with dislocation simulations based on calculations of the stress fields around the pads. We find that the simulated configurations match well with the experimental data, and we show that the dislocation configuration can be controlled by the pad size