Role of 1,2,4-Triazole in Co/Cu Removal Rate Selectivity and Galvanic Corrosion during Barrier CMP

Abstract

Removal rate selectivity control and galvanic corrosion reduction between cobalt (Co) and copper (Cu) are two challenges during cobalt barrier chemical mechanical polishing process in copper interconnects. This paper focuses on the investigation of a typical inhibitor 1,2,4-triazole on Co/Cu removal rate selectivity and galvanic corrosion under alkaline conditions. It is revealed that the selectivity of cobalt removal to copper is improved by accelerating the cobalt removal at low 1,2,4-triazole concentration, and then the removal rate of both metals is inhibited as 1,2,4-triazole further increased at 0.5 wt% colloidal silica concentration. Based on results, the inhibition action of 1,2,4-triazole was proposed. 1,2,4-TAH and 1,2,4-TA− species exist and account for at pH 10, then physical adsorption between 1,2,4-TAH and copper or cobalt atom via N4 site and chemical adsorption between 1,2,4-TA− and metal cation by sharing nitrogen atoms with a free electron pair in triazole ring occur on the two metals surface, resulting in copper and cobalt inhibited. The corrosion inhibition efficiency (IE) and corrosion potential difference (△E) was obtained from the potentiodynamic polarization plots. The results indicate that 1,2,4-triazole is an effective inhibitor both for chemical and galvanic corrosion.