Ruthenium and Copper CMP in periodate-based slurry with BTA and K2MoO4 as compound corrosion inhibitors

The Copper (Cu) wiring and barrier layer Ru (Ruthenium) CMP is of vital importance to the performance of microchips. For fabricating Ru-Cu interconnect structures, a serious challenge is the galvanic corrosion of Cu that occurs during Ru chemical mechanical polishing (CMP). Previous work has presented a calculation approach to evaluate the galvanic corrosion of Cu in slurry with KIO₄ as the oxidizer. Potassium molybdate (K₂MoO₄) combined with benzotriazole (BTA) acts as the inhibitor and the synergetic effect during CMP has been investigated. The work in this paper makes further improvement in the CMP performance using K₂MoO₄ and BTA as corrosion inhibitors for Cu and Ru. Results show that the pH value, the oxidant and inhibitor concentration could significantly affect the CMP performance. The material removal rate (MRR) selectivity between Cu and Ru has been optimized by adjusting the slurry composition. Results show that in BTA contained slurry with KIO₄ as oxidant, the addition of K₂MoO₄ helps to obtain good MRR selectivity between Cu and Ru. BTA-K₂MoO₄ acts as good corrosion inhibitor for Cu and has complexation effect for Ru during CMP.