An investigation of process dependence of porous IMD TDDB

Process sensitivity of IMD TDDB in a vertical natural capacitor (VNCAP) structure was evaluated in this paper. Among others, CMP slurry and wet clean chemical were found to have higher level of interaction impacting TDDB performance. This enables proper process optimizations, such as reduction in the Cu+ concentration on ULK top surface. Additionally, dependence of the structure was analyzed and the top metal layer is identified as the weakest link in VNCAP failure. A solution for this was described and it involves accelerated thermal cure step which successfully recovered dielectric electric strength.