Understanding the Dishing Difference Between a Line and a Bond Pad in Cu CMP

In Cu chemical mechanical polishing (CMP), dishing for a line differs from that of a bond pad. Even if the linewidth and the side length of a square pad are the same, dishing in a line is much more severe than dishing in a pad. In this paper, we show that pad deformation may be the reason. Pad deformation over a line is primarily restricted by two sides of its surrounding areas, while pad deformation over a pad is restricted by all four sides of its surrounding areas. Therefore, it is easier for the polishing pad to touch the Cu in a line than in a bond pad, which increases dishing. The result is also verified against experimental data. © 2003 The Electrochemical Society. All rights reserved.