Effect of low-k dielectric on stress and stress-induced damage in Cu interconnects
The effect of low-k materials on the stress and stress distribution in vialine structures of dual damascene Cu interconnects were analyzed using three-dimensional finite element analysis. For this purpose, vialine structures incorporating two different dielectric materials, tetraethyl orthosilicate (TEOS) and organic polymer-based low-k materials, were investigated. In the case of TEOS, which has a relatively low coefficient of thermal expansion (CTE) and a high elastic modulus, hydrostatic stress was concentrated at the via and the top of the lines, where it was suspected that the void should nucleate. On the other hand, in the vialine structures integrated with organic low-k materials, which have higher CTE and very low Young's modulus, large von Mises stress is maintained at the via, and thus the deformation of the via, rather than voiding, is the anticipated main failure mode. A good correlation between the FEM prediction and experimentally observed failure was obtained in the different dielectric materials.
low-k stress damascene cu fem