Study On Weakly Alkali-polished Slurry And Control Mechanism Of Planarization For Integrated Circuit Cobalt Plugs

At present,the integrated circuit is in the stage of large-scale(GLSI)development.Traditional tungsten plug can no longer meet the performance requirements of the device,and the cobalt(Co)material has become 7 nm due to its small resistivity and good trench fill ratio.Chemical mechanical planarization(CMP)is one of the key technologies to realize the application of cobalt plugs in integrated circuits,and the rough polishing step of cobalt is the key technical foundation for achieving the cobalt plug flattening,which directly determines the final CMP quality.However,there is lack of in-depth research on the rough polishing of cobalt plugs and its planarization mechanism at home and abroad,which needs to be further improved.This paper aims at the requirements of high-speed,low static corrosion and high planarization of integrated circuit cobalt plugs and the deficiencies of research at home and abroad.,the following research is carried out:In this paper,nano-silica(Si O₂)is used as the abrasive,hydrogen peroxide(H₂O₂)is used as the oxidant,and pentapotassium diethylenetriaminepentaacetic acid(DTPA-5K)is used as the complexing agent to achieve a high removal rate of integrated circuit cobalt plug(RR).Aiming at this system,the effect of H₂O₂and DTPA-5K synergism on Co removal rate and static corrosion rate(DR)was first studied.The results show that DTPA-5K can effectively increase Co RR,and as the concentration of DTPA-5K increases,Co RR increases first and then tends to be flat;as the concentration of hydrogen peroxide increases,Co RR increases first and then decreases.Secondly,electrochemical,X-ray photoelectron spectroscopy surface element analysis(XPS)and ultraviolet-visible spectroscopy analysis(Uv/vis)and other methods are used to reveal the mechanism of DTPA-5K complex removal by Co.The results show that as the concentration of DTPA-5K increases,the corrosion potential of Co decreases,the surface oxide layer becomes thinner,and Co RR is accelerated.Combined with XPS surface material analysis,after adding DTPA-5K,the surface produces[Co₄R(C₆H₅O₇)₂]²⁺,[Co₄R(C₆H₅O₇)₂]³⁺,the formation of these two substances has a great relationship with the high Co RR.In response to the DR and high planarization requirements of the cobalt plug,the corrosion inhibitor 5-carboxybenzotriazole(CBT)was introduced into the polishing solution to study the effect of CBT concentration on the polishing rate of cobalt,static corrosion and surface condition.The results show that as the concentration of CBT increases,Co RR and DR both decrease.Scanning electron microscope(SEM)and XPS were used to analyze the morphology and elemental analysis of the material surface,revealing the passivation mechanism of CBT on Co surface,indicating that the presence of CBT can form passivation on Co surface.The film effectively protects the surface of Co and inhibits the removal of Co.The sensitivity of CBT to process parameters is also studied,which shows that the suppression effect is better at low pressure and low speed,and the Co RR and process parameters exhibit non-linear changes,providing a theoretical and technical basis for the next generation of cobalt plug high flattening.