Preparation And Application Of CeO₂ Composite Abrasives In Chemical Mechanical Polishing

Chemical mechanical polishing(CMP),an essential part of IC manufacturing,enables ultra-precise surface processing and is the only commercial technology at present that can take into account local and global flattening of semiconductor wafer surfaces.However,with the reduction of chip feature size and the improvement of integration,higher requirements are put forward for the flatness of polished surface.Therefore,the synthesis of abrasives is no longer limited to a single material,and the preparation of high-efficiency and high-quality composite abrasives has certain scientific significance and practical application value.In view of this,we have established a complete CMP experimental platform,designed and synthesized new core-shell,porous and doped CeO2-based abrasives.Furthermore,the preparation and characterization of abrasives,the formulation and evaluation of polishing slurry,and the testing of polishing performance were investigated.The aim is to provide a systematic and complete program for the development of CMP materials and to optimize the performance evaluation system of polishing slurry.Details are as follows,(1)Core-shell abrasives:The polystyrene core was synthesized by emulsion polymerization,subsequently coated with CeO2 and doped with La,Nd,and Eu ions.The structural and optical characterization of the material were completed.Nd-doped abrasives were selected for polishing slurry,and the mechanism of surfactants to enhance the stability was explored.Subsequently,the effect of photocatalysis on the polishing rate of SiO2 was investigated by polishing experiments.Based on the structural defect characterization and radical trapping tests,possible polishing mechanisms were proposed.In this work,high performance CeO2 core-shell abrasives and environmentally friendly CMP slurry were obtained,and a complete scheme for material development was provided,which could be a guide to the design and synthesis of new CMP materials.(2)Porous abrasives:Monodisperse porous CeO2 nanospheres were synthesized by hydrothermal method and modified by Nd doping.The influence of doping amount and heat treatment on the morphology and structure of the abrasives were investigated.Structural and optical characterization verified the enrichment effect on surface defects(Ce3+,oxygen vacancies)by doping modification.Eventually,the effect of doping modification on material removal rate was investigated by polishing performance test.In this work,excellent doping and calcination processes were determined to provide feasible programs for the preparation and modification of porous abrasives.(3)Doped abrasives:La,Nd and Eu were doped into pure CeO2 by impregnation to explore the impact of ionic doping on the morphology and structure.Besides,the suspension stability of different CMP slurries was researched.In this work,we obtained highly dispersible CMP polishing solution,which is of reference value in the development of non-toxic and non-hazardous polishing slurry.