金属原子集積とナノ・マイクロ構造体形成に起因した絶縁保護膜の損傷挙動解明

抄録

The passivation is a key component of interconnections in the electronic devices because it works as an electrical insulator and a shield against mechanical deterioration and chemical corrosion. In the interconnections, the accumulation of atoms due to electromigration (EM), which is the physical phenomenon of atomic diffusion with high density electron flow, causes the passivation fracture through the formation of nano/micro-structures. The passivation fracture threatens the reliability of electronic devices because the open/short circuits caused by the failures of interconnections are easily formed. One of the countermeasures to prevent fracture initiation of passivation is the deposition of thicker passivation. Although the study of passivation thickness is important because the increase in the passivation thickness would increase the resistance against the passivation fracture and the reliability of interconnections, the effect of the passivation thickness on the lifetime of interconnections against EM has been still qualitatively reported so far. The clarification of the failure mechanism of nonconductive passivation is required to propose the suitable passivation thickness against the passivation fracture by accumulation of atoms. In the present study, to propose the strategy for determining the suitable passivation thickness, the effect of passivation thickness on passivation fracture is examined through the experiments using an Al line covered with tetraethyl orthosilicate passivation. The behavior of passivation fracture with passivation thickness is newly formulated and can be explained by considering the critical tensile stress in the circumferential direction at the inner wall of a long cylindrical tube subjected to internal pressure. A suitable passivation thickness for required resistance against passivation fracture can be determined based on this finding.