Study Of Planarization Of GLSI Multilayer Copper Wiring With Chemical Dominated Alkaline Polishing Slurry

The continuous development of great-large-scale-integrated circuit?GLSI?puts forward more stringent requirements for chemical mechanical planarization?CMP?:low mechanical strength,low roughness,high smoothness and high cleanliness.BTA?Benzotriazole?was added in the commercial slurry to achieve the planarization,resulting in high polishing mechanical strength,difficulty cleaning,equipment corrosion and high cost.It is a frontier technology in the field of microelectronics manufacturing to research the novel inhibitors-free alkaline slurries with the chemically dominant,simple process,low cost and environmental protection.Firstly,a theoretical model of copper slurry for planarization has been established in the energy and chemistry perspectives,respectively.And the self-passivation theory of alkaline polishing slurry has also been proposed,which explains why Cu₂O,CuO and Cu?OH?₂ are insoluble under inhibitors-free alkaline conditions and thus passivate the copper at localized valley area in CMP process.Under the guidance of the self-passivation theory,the optimum proportion of rough polishing and clearing polishing slurry containing FA/O chelator were determined through a large number of experimental studies,and a set of process parameter that matches the machine of 65nm industry product line has been optimized.Compared with the widely used glycine,the 65nm industry product line test results showed that the inhibitors-free alkaline slurries containing FA/O chelator could get the higher planarization efficiency,and the extension of dishing was effectively controlled,so the theory of self-passivation is proved.Secondly,the barrier slurry free of oxidizers and inhibitors has been developed by appling the theory of amination,mass transfer theory and complexing theory,and controllability and adjustability of removal rate selectivity for different materials has been realized.Compared with the commercial barrier CMP slurry of the 65nm industry product line,the parameters such as dishing,erosion,resistance,capacitance and leakage currents after polish are better than commercial ones.Besides,the barrier slurry free of oxidizers and inhibitors exhibits a stability having a long shelf life and is favorable for the post-CMP cleaning,which promotes barrier CMP requirements for 65 nm technology node.At the end,this thesis carried out studies aiming at the instability of the inhibitors-free alkaline copper slurry and large numbers of defects introduced by the barrier slurry free of oxidizers and inhibitors.According to the study,in addition to the decomposition of H₂O₂,the root cause of instability of slurry is the chemical reaction between H₂O₂ and FA/O chelating agent.AFM?atomic force microscopy?testing results demonstrated that defects on wafer surface polished with the barrier slurry without oxidizer and inhibitors are micro-scratches.The polishing results indicated that the root causes for micro-scratches are the large particle exceeding 0.5?m size in the slurry,and scratches are remarkably reduced by installing a 0.2?m size filter and choosing the abrasive of lower particle-size dispersity without affecting the CMP performance,then the polishing results meet the requirements of the 65nm industry product line.