Effect of Novel pH Regulators on Copper film Chemical Mechanical Polishing for Ruthenium-Based Copper Interconnect under Weak Alkalinity Conditions

Abstract

For Ruthenium (Ru)-based copper (Cu) interconnects Cu film chemical mechanical polishing (CMP), it is crucial to select appropriate pH regulators in the slurry to ensure the chemical reactions and maintain the stability of the polishing chemical environment. In this study, the effects of inorganic pH regulator KOH, organic pH regulator diethanolamine (DEA), and 2-amino-2-methyl-1-propanol (AMP) on CMP and slurry properties of Cu film were compared. It was found when using AMP as a pH regulator, the Cu/Ru removal rate selectivity (RRS) can reach 598:1, the surface roughness of Cu film decreased to 0.76 nm, and the slurry can remain stable for at least 7 d. The performance order of the three pH regulators is AMP＞KOH＞DEA. Meanwhile, through experimental results and test analysis, it has been confirmed that AMP can also play a multifunctional role as a complexing agent, dispersant, and surfactant. Therefore, AMP can replace KOH as a new pH regulator in weak alkaline slurries. This result plays an important role in guiding the selection of organic pH regulators in the optimization of Cu film CMP slurry. Highlights For Ruthenium-based copper interconnects copper film chemical mechanical polishing, it is crucial to select appropriate pH regulators in the slurry to ensure the chemical reactions and maintain the stability of the polishing chemical environment. In this paper, diethanolamine and 2-amino-2-methyl-1-propanol were selected as organic pH regulators for the properties of eco-friendly, stable, rapid reaction performance and the effects on copper film chemical mechanical polishing. 2-amino-2-methyl-1-propanol can also play a multifunctional role as a complexing agent, dispersant, and surfactant. When using AMP as a pH regulator, the copper/Ruthenium removal rate selectivity can reach 598:1, the surface roughness of copper film decreased to 0.76 nm, and the slurry can keep stability for at least 7 d. The application of multifunctional organic alkali in copper film chemical mechanical polishing will get more and more attention.