Effect of ceric ammonium nitrate on chemical mechanical polishing of graphite for potential applications in integrated circuits

Graphene is a promising interconnect material for future integrated circuits (IC). Nevertheless, challenges remain in developing processing techniques compatible with IC manufacturing processes, such as chemical mechanical polishing (CMP). This study investigated CMP of graphite, a multi-layer system of graphene. The results reveal that ceric ammonium nitrate (CAN) achieves the highest material removal rate (MRR) of graphite among the five tested oxidants, probably due to its strong oxidizing capacity. Moreover, the MRR of graphite increases and then decreases as the CAN concentration increases. With 0.45 wt% CAN, the MRR peaks at 436.6 nm/min, with a mirror-like finish. For the material removal mechanism, within the low CAN concentration range, an oxide film with lower mechanical strength than graphite forms on the graphite surface. Therefore, the MRR increases. By contrast, within the high CAN concentration range, the oxide film exhibits a higher content of the C=O bond, demonstrating greater structural stability and mechanical strength, leading to lower wear. Additionally, the generated CeO 2 can form Ce-O-Si bonds with silica abrasive, making abrasive harder to wear away the oxide film. Consequently, the MRR decreases. The findings could guide graphene CMP. Using strong oxidation and a matched mechanical force may achieve near-zero-defect and controllable removal.