A study on sputtering of copper seed layer for interconnect metallization via molecular dynamics simulation

Interconnects are significant elements in integrated circuits (ICs), as they connect individual components of the circuit into a functioning whole. To form a void-free interconnect, a thin and uniform copper seed layer must be deposited as a basis for electroplating. In this paper, process parameters of sputtering including incident energy, incident angle, substrate temperature, and deposition rate were studied to form a uniform copper seed layer. Different liner/barrier materials and properties including crystal planes were also studied to enhance the quality of the copper seed layer. The study was carried out by molecular dynamics simulation. It revealed that increasing the incident energy and substrate temperature during the sputtering process increases their diffusivity but results in poorer uniformity and larger alloy percentage. By decreasing the deposition rate, the Ostwald ripening effect becomes dominant and increases the uniformity. An adequate incident angle could increase necking and uniformity. Among the sputtering process parameters and material properties discussed in this study, surface diffusion barrier energy of different crystal planes is the most decisive factor, which leads to good uniformity.