Characterization of patterned low-k film delamination during CMP for the 32nm node Cu/ultra low-k (k=1.6-1.8) integration

Pattern dependence of ultra low-k (ULK, k=1.6-1.8) film delamination during Cu-CMP has been investigated to integrate the 32 nm node Cu/ULK damascene interconnects. A CMP mask that has various kinds of dummy-patterns was developed for quantitative characterization of the ULK film delamination. As a result, the perimeter of the pattern, which is the length along the boundary between Cu and low-k film, was found to be a determinative parameter in delamination of the patterned low-k film rather than pattern density. This is because Cu interconnects with higher-density perimeter increase the tolerance to shear stress generated by the CMP, and thus prevent the delamination due to the low mechanical strength of the ULK film (modulus; E<2GPa). A soft pad polishing was also effective in suppressing the mechanical damage. On the basis of these results, Cu damascene interconnects with ULK film were successfully integrated on 300mm wafers.