Effects of pyrazine and its derivatives as inhibitors on copper film chemical-mechanical polishing properties for ruthenium-based copper interconnect

Abstract

During the one-step chemical mechanical polishing (CMP) process of ruthenium (Ru)-based copper (Cu) interconnected Cu films, a high Cu removal rate (RR) while maintaining a near zero Ru RR should be required to ensure a flat surface. The most ideal and difficult part of the CMP process is how to achieve rapid removal of Cu film without affecting Ru layer. Corrosion inhibitors in the slurry fulfill a significant function in controlling RR and improving the surface quality. Therefore, in this study, pyrazine (PY) and its derivative aminopyrazine (AP) as cost-effective and harmless corrosion inhibitors for Ru-based Cu interconnected Cu film CMP were investigated under weakly alkaline conditions (pH=8.5). First, through the utilization of experimental and theoretical methods, a systematical analysis was conducted to assess the corrosion inhibition effects of AP and PY, and it was found that the corrosion inhibition effect of AP was stronger than that of PY. Then, the adsorption and inhibition mechanism of AP on Cu/Ru surface were analyzed by electrochemical testing and X-ray photoelectron spectroscopy (XPS), and the adsorption behavior of AP molecules on the Cu (111) surface was investigated at the molecular level using quantum chemical methods. Finally, tests on Cu patterned wafers showed that the combination of 0.5 wt% AP and 0.5 wt% sarcosine (Sar) proved to be successful in effectively rectifying the step height on the Cu patterned wafer. At the same time, a high RR of 7281 Å /min, a low surface root mean square deviation (Sq) of 1.35 nm in 10 μm×10 μm region and a low static etching rate (SER) of 1015 Å /min were obtained with the synergistic effect of AP and Sar. This outcome holds substantial theoretical implications for advancing the formulation of low-node Cu film slurry.