Effects of mixed inhibitors in copper chemical mechanical polishing at a low down pressure

The individual and synergistic effects of benzotriazole and sodium dodecyl sulfonate on copper disc are investigated at a down pressure of 3.4kpa. The corrosion rate is reduced by using benzotriazole, but the surface quality is poor owing to the slow formation rate of copper-benzotriazole protection film. For sodium dodecyl sulfonate, the corrosion rate is further reduced, but slight corrosions can be still observed due to the incomplete coverage of sodium dodecyl sulfonate molecules. The combination of sodium dodecyl sulfonate and benzotriazole leads to the maximum decrease of corrosion rate. Under the benzotriazole/sodium dodecyl sulfonate ratio of 1:3, the average roughness achieves as low as 1.025nm owing to the soft and dense coverage of benzotriazole/sodium dodecyl sulfonate molecules. Besides, the trends of removal rate, roughness and friction coefficient are proved to be similar for copper discs and copper wafers in slurries with different inhibitors. Therefore, the results presented here are relevant for further developments in the area of low-pressure chemical mechanical planarization of copper lines overlying fragile low-k dielectrics in the new interconnect structures.