Study On Interface Corrosion Of Barrier Layer Cobalt Chemical Mechanical Polishing For GLSI Multilayer Copper Wiring

As technology nodes decrease to 14nm and below,in order to meet the needs of the development of integrated circuits,cobalt replaces Ta of poor performance due to its lower resistivity,good step coverage,good adhesion,and resistance to copper diffusion.Cobalt has become one of the new barrier materials.International acidic polishing solution with mass-application adds inhibitors?BTA?to achieve planarization,resulting in high polishing mechanical forces,difficulty cleaning,equipment corrosion,and high cost.It is an international technical challenge to urgently develop alkaline slurries without BTA.In this paper,using single-factor experiments and orthogonal experiments,the influence laws and mechanisms of the galvanic corrosion of cobalt-copper interface by components such as pH value,H₂O₂,FA/O chelating agent,AESA,1,2,4-triazole and others under FA/OII and FA/OI chelating agent systems had been studied by the use of ionization,chelation,adsorption,oxidation,and passivation theories and characteristics of surfactants.And the CMP slurry with the smallest interface galvanic corrosion was studied.Simultaneously,it was confirmed by polishing experiment that it also had a good rate selectivity.At the same time,the stability of the polishing slurries composed of different concentrations of FA/OII and 0.1%H₂O₂,and the polishing slurries containing surfactant and 1,2,4-triazole were studied from the perspective of contact corrosion potential using electrochemical method.It was found that when the slurry components were 0.5wt%silica,0.05%FA/O chelating agent,0.1%H₂O₂,345ppm 1,2,4-triazole,the Co/Cu interface corrosion potential difference was reduced to 1mV,the galvanic corrosion current density from the usual few?A·cm^-22 decreased to 0.02nA·cm^-2,which effectively reduced the interface galvanic corrosion.At the same time,the ratio of cobalt to copper was 1.32:1 at low pressure?1psi?and low abrasive?0.5%?,which can helpfully correct dishing and erosion.Based on the above studies,in order to obtain better stability,the galvanic corrosion of Co/Cu interface by various components based on glycine system were studied,and the components with smaller galvanic corrosion were investigated in terms of polishing and static corrosion.And the stability increased from 5 days for FA/O chelator system to 21days.It has provided theoretical guidance for more in-depth study of 14nm and below in the Co CMP.