The influence of texture on the reliability of aluminum and copper interconnects

Texture in films develops during deposition processes and annealing of patterned wafers. Recent studies show that texture influences the performance and reliability of both aluminum and copper interconnects. To improve the current understanding of this matter, the influence of texture on reliability was studied.; The influence of texture on electromigration and stress-induced failures in aluminum interconnects was studied since these are the most often responsible for failures observed in aluminum interconnects. Results obtained showed that a strong {lcub}111{rcub} texture in aluminum interconnects improves their median time-to-failure. The grain boundary character distribution and percentage of coincidence site lattice (CSL) boundaries, was quantified using orientation imaging microscopy. It was found that the median time-to-failure of specimens increased as the number of low angle and CSL boundaries increased. These boundaries are known to have low diffusivity. It was also demonstrated that while the investigated specimens had grains of comparable size, the grains of similar orientations were clustered in the specimens having the stronger {lcub}111{rcub} texture. This phenomenon contributed to the longer median time-to-failure of the interconnects by reducing the frequency of high angle grain boundaries. The experimental data obtained shows that the residual stress in films decreases as the intensity of the {lcub}111{rcub} texture increases. A model based on Monte-Carlo simulation of texture formation during the deposition of aluminum film was proposed to suggest the optimum conditions for a growth of a strong {lcub}111{rcub} texture component. A low deposition rate and a high mobility of atoms on the surface, which corresponds to a high substrate temperature, can strengthen {lcub}111{rcub} texture.; Copper has been recently used as an interconnecting material because of its good electromigration resistance and low electrical resistivity. One of the major problems of copper as an interconnecting material is that it easily oxidizes at relatively low temperatures. The formation of oxide degrades the electrical and mechanical properties of copper interconnects.{09}The influence of substrate texture on the oxidation kinetics was studied to suggest methods to reduce copper oxidation. Copper single crystals having (100), (110), (123), (314), (111) and (311) orientations were oxidized at 200°C in air. Only the Cu₂O phase was formed during oxidation. The oxidation of the (100) single crystal substrate was much faster than that of the others. This is attributed to a large number of fine oxide grains on the (100) crystal in the initial stages of oxidation. It is recommended that the {lcub}100{rcub} texture in copper interconnects should be avoided in order to reduce oxidation rate. A quantitative model was proposed to predict the oxidation kinetics of copper from the texture of the specimens. Reasonable agreement was obtained comparing the model predictions and the experimental results obtained from the test of oxidation of polycrystalline copper specimens. However, further improvement of the model can be done if more data from single crystal experiments are obtained.