Role of Potassium Tolyltriazole as an Inhibitor in H₂O₂-Based Slurry on Cu/Ru Patterned Wafer CMP

Abstract

In the process of chemical mechanical planarization (CMP) during copper interconnection fabrication, the inhibitor in the copper slurry plays an important role in obtaining a good planar surface after CMP. In this paper, a kind of corrosion inhibitor TTAK was introduced in H2O2-based alkaline slurry. The experimental results show that the addition of TTAK can effectively reduce the removal rate (RR) and static corrosion rate (SER) of copper. As the increase of TTAK concentration, the passivation effect is enhanced. The passivation mechanism of TTAK was characterized by electrochemistry and XPS. The results show that TTAK can reduce the corrosion rate and removal rate of copper by absorbing on copper surface to form passivation film. On the contrary, it has no significant influence on Ru. In addition, the dishing and erosion of Ru/Cu structure based patterned wafers were further tested. The experimental results show that the introduction of TTAK can effectively reduce the dishing and erosion depth of different line width and spacing.

Effect of Potassium Ferrocyanide on CMP Performance of Ruthenium in H2O2-based Slurries

“…The decrease in the corrosion potential indicates a weakened protective effect of the passivation film on the Ru electrode surface, making the electrode surface susceptible to erosion by corrosive particles in the solution. 29,38 In addition, as the concentration of K 4 Fe(CN) 6 increases, the corrosion current density gradually increases (from 5.8 μA cm −2 to 125.6 μA cm −2 ), indicating an enhanced corrosive effect of the solution on Ru and an accelerated oxidation and corrosion rate of Ru in the solution. It can be observed from Table II that when the concentration of K 4 Fe(CN) 6 is varied from 7.5 mM to 10 mM, there is a most pronounced change in the corrosion current density.…”

“…27 Although ruthenium, being a promising barrier material, has many of the aforementioned advantages, chemical mechanical polishing(CMP) after deposition of ruthenium barrier is challenging as a consequence of its high mechanical hardness(6.5 Mohs) and strong chemical inertness, which pushes the approach to actualize high removal rate of ruthenium towards screening for powerful and valid oxidizers. 15,17,26,29 In early research, the removal rate of ruthenium over 60 nm min −1 was successfully attained by using ceric ammonium nitrate, potassium bromate or potassium peroxymonosulfate as an oxidizer under the condition of strong acid (pH ⩽ 2) and high down-pressure(>5 psi). 30 It must be pointed out here that barrier CMP is not recommended to be accomplished using a highly acidic polishing slurry to avoid excessive corrosion of the adjoining copper wiring.…”