Influence of post-CMP cleaning on Cu interconnects and TDDB reliability

The etching amount of Cu wires produced by post-chemical-mechanical polishing cleaning was studied. By using polyvinyl alcohol brush cleaning, the cleaning strength concentrates on the center chip of the wafer, which leads to the erosion of Cu interconnects. The etching depths of isolated Cu wires and dense Cu wires were compared. The surface on the isolated Cu wires is etched deeply because of the nonliner diffusion of the solution and the difference between the friction strengths of both wire patterns. These etching depths were improved by optimizing the brush formation, the rotation speed of the roller and the brush, and by using organic-acids. With respect to the dependence of time-dependent dielectric breakdown (TDDB) lifetime on waiting time, there is a difference between the diluted hydrofluoric-acid (DHF) and organic-acid solutions. The TDDB lifetime for the DHF cleaning is similar until after a waiting time of ten days, whereas the TDDB lifetimes for organic-acids are similar until after a waiting time of four days.