The Contributions of Barrier Resputter for BEOL Integration

Abstract

For Cu interconnect, Ta(N) barrier is widely used. In this work barrier resputter process was studied. Related wafer acceptance test (WAT), via pouch through, profile of Dual Damascene structure and via electron migration (EM) was investigated. Resputter removes the high resistive Ta(N) from the bottom to lower the via Rc. Barrier first process, including Ta(N) deposition and aggressive resputter, is widely used. Aggressive resputter enlarges top CD of trench and via. That makes gap fill easier and even lower via Rc. Aggressive resputter is helpful to via clean and enhances downstream electro migration (EM) performance. Resputter can change the geometry of dual damascene structure. Such a geometry change has large impact on the upstream electro migration (EM) performance. Barrier resputter also has its shortcoming and limitation. For punch through process, Cu sputtered from the bottom redeposits on the side wall, which may have negative impact on upstream EM performance. Resputter also causes damage to low-k material, with such damage metal line capacitance and reliability may become problem. For Cu interconnect, to manage resputter properly is a key factor to the succeed of back end of line (BEOL).