Role of slurry chemicals in chemical-mechanical planarization of copper interconnects.

摘要

Chemical mechanical planarization (CMP) has emerged as the viable planarization technique for copper damascene and dual damascene interconnect processing as well as shallow trench isolation process.; The demand for a chemically driven rather than a mechanically driven Cu CMP process has increased with the integration of low-k dielectrics in integrated circuit (IC) chips. Though many chemicals have been identified as potential additives for copper CMP slurries, a fundamental understanding of the interactions between these chemical reagents and copper thin films and their relation to defects in the polished films is poorly addressed in the literature. This work aims at mainly investigating the role of complexing agents in copper CMP slurries.; Several organic acids including glycine and citric acid, as complexing agents in hydrogen peroxide based slurries are being investigated and their chemical interactions with Cu in the presence of H2O2 are being correlated with the material removal rates and defect formation. Copper dissolution and polish rates and electrochemical experimental results at different chemical compositions are performed. It has been observed that the ability of the complexing agents to form stable soluble complexes with oxidized Cu, the functional groups of the complexing agents such as (-COOH) and (-NH2), and the pH of the slurry/solution not only affect copper removal rates but also the type of defects formed during CMP.; Packed bed column technique has been used to investigate the interactions between the chemicals in the slurry and copper surface. The packed column technique allows the elucidation of mechanisms of chemical reactions between copper and solutions injected into the column. Based on such experimental results and their theoretical interpretations, a better understanding of the chemical interactions between copper and glycine + H2O2 has been gained from a chemical point of view and these phenomena are being related to Cu CMP process.; Mechanism of Tantalum Nitride (TaN) CMP in alkaline H2O 2 based slurries has been investigated using Fourier transform-electrochemical impedance spectroscopy (FT-EIS) technique. The preliminary results suggested that the TaN removal mechanism may be similar to that of Tantalum under identical conditions. The catalytic decomposition of H2O2 on the metal surface at alkaline conditions to OH-, causing an enhancement in the local concentration of the latter plays a vital role in dissolving Ta2O5 surface species most probably in the form of hexatantalate ion Ta6O198- .