Barrier Metal Slurry for Low Defect Copper Damascene Chemical Mechanical Polishing

Wednesday, 8 October 2014: 11:20
Expo Center, 1st Floor, Universal 13 (Moon Palace Resort)
H. Kim, K. Seo, J. Moon, H. Kim, and H. Hwang (Memory Clean/CMP Technology Team, Samsung Electronics)
In the semiconductor process, chemical mechanical polishing/planarization (CMP) is inevitable in copper (Cu) interconnect forming. Cu damascene scheme is achieved by help of CMP to form highly ordered metal lines.
As the CMP process uses a set of partial polishing steps to complete a damascene structure, slurries of each partial step is designed to have different performances to that of other steps. Among the steps, final partial step, so called, barrier metal (BM) CMP is a critical step because it determines the superior flat finish.
In the BM CMP, a structure consists of heterogeneous materials such as Cu, dielectric oxide, and BM should be polished at once. Thus, abrasive suspended in the BM slurry should be optimized to achieve the superior flat finish.
In the present study, 3 kinds of BM slurry were utilized. Abrasive of those slurries are made of colloidal silica in the size of 30 nm to 60 nm. The abrasive surfaces, however, are differently modified to have suitable performance for various polishing environments. The modification involves shape of abrasive, chemical additive to increase suspension stability, coating with polymers, and operation pH. Their effects on the CMP performance not only for blanket wafers but also for pattern wafers having 2x nm pitch were observed experimentally. The results indicated that not only polishing performance but also defect occurrence, which is important in mass fabrication, should be considered equally. Finally, strategy for reducing defect occurrence while maintaining Cu damascene performance will be discussed.