When the technology node is reduced to 32 nm or below, new barrier layer materials are urgently needed to alleviate the problem of poor reliability of copper (Cu) interconnection devices caused by resistance-capacitance (RC) delay. Compared with tantalum (Ta), cobalt (Co) has the advantages of lower resistivity, smaller hardness, better adhesion to Cu, and conformal deposition in high aspect ratio trenches. Therefore, Co becomes a promising liner material to replace Ta and is stacked on the tantalum nitride (TaN) barrier layer. The introduction of Co can reduce the thickness of the barrier layer and simplify the process. However, when the technology node is reduced to 10 nm and below, the metal line width approaches or even becomes smaller than the electron mean free path of Cu. Due to the increase in electron scattering at the sidewalls and grain boundaries, the resistivity of Cu begins to increase sharply. Compared with Cu, Co has a lower electron mean free path and can work with a thinner barrier. Therefore, Co becomes an excellent candidate material to replace the contact metal tungsten in the middle of line (MOL) and the interconnect metal copper in the back end of line (BEOL). The introduction of Co will inevitably require processes that are compatible with chemical mechanical polishing (CMP) and cleaning after CMP. However, the slurry formulation (as a trade secret) compatible with the multi-layer Cu interconnection Co-based barrier layer CMP and the Co interconnection CMP has not been disclosed. At the same time, the academic circles lack systematic and comprehensive research on Co CMP. This paper systematically discusses the effectiveness and feasibility of Co as the Cu interconnection barrier and the interconnection metal. The research status of Co-based barrier layer and Co interconnection CMP is mainly reviewed, and the influence of different chemical additives on material removal rate, corrosion protection, galvanic corrosion and removal rate selectivity is discussed. At the same time, the problems and challenges faced by Co CMP are summarized to provide a valuable reference for the development of Co-based barrier layer and Co interconnect CMP slurry. © 2022, Materials Review Magazine. All right reserved.
