Mechanism of void formation in TiN/AlSiCu/TiN/plasma-enhanced tetraethyl orthosilicate SiO2 multi-layer structures via high-temperature stress migration

In this study, the mechanism of void formation in the Al metal lines of TiN/Al-1%Si-0.5%Cu/TiN anti-refraction coating multi-layer structures has been investigated. The produced voids exhibited distinct characteristics (such as the presence of silicon nodules) and did not possess conventional shapes (such as notch-type or wedge-type ones). In addition, the influence of the nitriding temperature of the TiN barrier film and stress generated in the upper plasma-enhanced tetraethyl orthosilicate (PE-TEOS) SiO2 layer on the void formation process was examined. When the compression stress of the upper PE-TEOS SiO2 layer was below that of the lower Al film during annealing, multiple dislocations were generated in the Al layer followed by the formation of vacancies during the recovery stage. Furthermore, the TiN barrier films formed by the nitriding of Ti layers via rapid thermal annealing at a temperature of 760 °C did not exhibit sufficient thermal stability and easily underwent plastic deformation during annealing, which promoted the formation of voids.