Study On Planarization Technology Of GLSI Multilayer Copper Interconnection

The development level of integrated circuit?IC?is an important symbol to evaluate industrial competitiveness and comprehensive national strength of a country.Chemical mechanical planarization?CMP?is the most complex process in IC fabrication,and it is the only technique to achieve the local and global planarization.As the first process of copper interconnection planarization,Cu CMP is the foundation of the multilayer wiring CMP,and its performance directly affects the subsequent processes.The alkaline copper CMP polishing slurry is the forefront of the development of microelectronics technology,which is applicable for industrial production needs.The oxidant H₂O₂ used in alkaline polishing slurry,without metal ions pollution,has significant influence on the reliability.Therefore,the stability,reliability and planarization performance of alkaline copper CMP polishing slurry are the core technologies of the international research,and it is also the focus of this research.Firstly,the alkaline copper polishing slurry of FA/O-H₂O₂ system,which was self-developed by the Institute of Microelectronics of Hebei University of Technology,was researched.By combining the stagnant layer theory,preferential adsorption theory,chelation theory and self-passivation theory which were used in copper CMP process,the effects of polishing slurry composition and polishing process parameters on copper CMP rate and surface uniformity were studied.The effects of SiO₂ abrasive,nonionic surfactant,oxidant and the synergistic effect of FA/O chelating agent and oxidant on the planarization performance were analyzed,and the planarization mechanism under alkaline condition was discussed deeply.It can achieve a good planarization effect without the addition of the corrosion inhibitor BTA.Meanwhile,the instability mechanism of the alkaline polishing slurry of this system was also researched.It is concluded that the FA/O chelating agent with strong reducibility in the slurry is the most important factor which results in the instability of the polishing slurry due to the consumption and decomposition of H₂O₂ under the alkaline condition.This provides theoretical guidance for the stability of alkaline CMP polishing slurry.Secondly,aiming at the instability of alkaline copper polishing slurry of FA/O-H₂O₂system,the new weakly alkaline copper polishing slurry of Gly-BTA system was studied.Through the study of the composition of the polishing slurry,the optimum proportion was selected to meet the industrial technical requirements of copper wiring chemical mechanical planarization.The mechanism of the dissolution/passivation of glycine and BTA in the polishing slurry under weakly alkaline conditions was studied by dynamic electrochemical experiment,and the planarization mechanism model in polishing process was established.Meanwhile,the stability of the polishing slurry of this system was researched.The experiments were carried out from the aspects of the configuration process,the pH value of the polishing slurry and the component concentration of the polishing slurry,and the optimization of the process and proportion improved the stability of the polishing slurry.The planarization performance and the stability of the polishing slurry of this weakly alkaline copper polishing slurry have significantly improved,which has great engineering application value in promoting the industrialization process of the Cu CMP polishing slurry in multilayer copper wiring.