Stress-induced voiding in stacked tungsten via structure

摘要

The stress-induced voiding (SV) in Al-alloy films with stacked tungsten via structures was investigted. Voids were found in interconnections wiht stacked and borderless vias that had resistance increase after the aging tests. Failure occures most frequently when the test structures are stored at approximately 250degC. This behavior can be explained by the diffusion creep model similar to SV in a flat line [].Finiteelementsimulations show that tensile stress in Al-lines between upper and lower plugs increases with temperature increase over 175degC. Al grains on W-plugs were found to have high-angle crystalline misorientation in transmission electron microscopy (TEM) observation. The tensile stress dn grain misorientation should accelerte the void growth during high temperautre storage. O_2 plasma post meal etch treatment is effective to eliminate SV in stacked via structure.