Evaluation of the Dominant Factor for Electromigration in Sputtered High Purity Al Films

Abstract

This paper is focused on evaluating the dominant factor for electromigration (EM) in sputtered high purity Al films. A closed-form equation of atomic flux divergence by treating grain boundary diffusion and hillock formation in a polycrystalline structure without passivation layer was derived to construct the theoretical model. According to the developed equation, it is available to see the effect of various parameters on the EM resistance. Moreover, based on the proposed model, we compared the EM resistance of different sputtered high purity Al films. These films differ in purity and features, which are realized as affecting factors for the EM resistance. Finally, according to the analysis by the synthesis of the obtained EM resistance, the evaluation of the dominant factor for EM in sputtered high purity Al films was approached. Although the effects of the average grain size and the effective valence cannot be ignored, the difference in diffusion coefficient was believed to have a dominant influence in determining the EM resistance. Thus, increasing the activation energy for grain boundary diffusion can significantly reduce the damage during EM in such sputtered polycrystalline Al films.

Fabrication of Al microtubes by electromigration and controlled etching

“…A 300 nm thick TiN layer was vacuum sputtered on the SiO 2 layer, and a 1200 nm thick Al film was vacuum evaporated on the TiN layer. The purity of the Al source material was 99%, and Al atoms can exhibit increased mobility under high current density and heating treatments [10, 11]. Al and TiN layers were patterned by wet etching, and the Al at the anode end of the line was etched to form a slit.…”

Analyzing electromigration near a right-angled corner composed of dissimilar metals by investigating the effect of material combination on atomic flux divergence

“…Because AFD essentially characterizes the EM-induced mass transport, the causes of AFD have been well studied on several target materials, [9][10][11][12][13][14][15][16] and formulations of AFD in strip and angled lines composed of a single material have also been achieved. [17][18][19] In contrast, a formulation of AFD near a corner composed of dissimilar materials, as described above, has not been reported. Because of the complicated nature of current density concentration and temperature field near the corner, numerical simulation is widely used for analyzing AFD in such a situation.…”