Study On Alkaline Copper Clearing Slurry And CMP Process Of GLSI Multilayer Copper Wiring

Referring to VLSI, 7nm and 28 nm products have been separately developed internationally and domestically. With the development of microelectronics, the improvement of integration density and interconnection layers become an inevitable trend. Chemical mechanical planarization(CMP) is recognized as the most effective way to achieve local and global planarization, which is widely used in IC manufacturing process. While, the introduction of the new material(low-k) and new structures(FINFET) put forward higher requirements. With the technology node shrinking, low pH, low abrasive concentration, low pressure were proposed by relevant International Institute. In cooper CMP, dishing and erosion as the key technical parameters is the bottleneck problem to be solved, which relates to the reliability of the interconnection. To achieve planarization, the international acid slurry need to add inhibitors, which needs high pressure to remove the BTA-molecular, causing severe damage to low-k layer. Simultaneously, BTA and its derivatives bring difficulties to the subsequent cleaning process. Therefore, novel alkaline slurry chemical prominently substituting mechanically dominant acid slurry is an inevitable trend. While, chemical dominant slurry has isotropic characteristic, leading to the copper loss in the recessed region highlights.In order to meet planarization relevant technical requirements, components of slurry(mainly composed of FA/OV and FA/OVI chelating agent) and polishing process were developed and optimized. The requirements of copper clearing polishing: high velocity selectivity of copper to tantalum, low dishing and erosion, removing residual copper effectively.The feasibility of the two kinds of alkaline slurries were analyzed theoretically. The removal rate, selectivity of copper to tantalum, uniformity and planarization were investigated through single factor experiments of slurry component and polishing process. The optimized slurry and process condition were applied in pattern wafer test. The effect of uniformity on planarization was achieved by comparing the FA/OII type slurry to FA/OV type slurry. Referring to FA/OVI type copper clearing slurry, the effect of synergic ratio of oxidant and chelating agent on planarization was analyzed through chemical-mechanical equilibrium and kinetic controlled processes.The results show that: FA/OV alkaline copper clearing slurry has good uniformity, the residual copper can be effectively removed and the value of dishing and erosion meets industrial requirements. The planarization was investigated during the over-polishing period of FA/OVI alkaline copper clearing slurry. The theoretical model of kinetic control process was proposed. The copper in the recessed region can be well passivated with the synergic ratio of oxidant and chelating agent in the interval(2.5-3.5).