Study On CMP Materials And Mechanisms Of Cu Interlayer Ruthenium Barrier Layer Based On H₂O₂ System

At present,the key technology nodes of Giga Scale Integration(GLSI)have been reduced to less than 7 nm.Traditional barrier material tantalum/tantalum nitride(Ta/TaN)has not been able to meet the development needs of integrated circuit(IC).Ruthenium(Ru)has become a research focus of new copper interconnect barrier materials due to its low resistivity and high reliability.However,due to the high hardness and chemical inertia of Ru,it is difficult to remove during chemical mechanical polishing(CMP),and the removal rate selectivity between many materials is difficult to control,which seriously affects the reliability and yield of the chip.In this paper,the removal rate selectivity and remove mechanism between the barrier layer material Ru,the wiring layer material Cu and the medium material TEOS(SiO₂ film)involved in the copper interconnect Ru barrier layer CMP of NH₄⁺-H₂O₂ slurry composed of new complexing agent NH₄⁺are studied in depth.The main contents are as follows:1.The effect of the synergistic effect of NH₄⁺and H₂O₂ on the removal rate of Ru/Cu/TEOS was studied.The study found that in the NH₄⁺-H₂O₂system,as the NH₄⁺concentration increased,the removal rates of the three materials increased.When the NH₄⁺ion concentration is 80 mM,the Ru removal rate can be increased from 130(?)/min to 690(?)/min.AFM test results show that the surface roughness of Ru after polishing is<1 nm;the removal rates of Cu and TEOS are also greatly improved.The stability results show that when the concentration of NH₄⁺is higher than 160 mM,the particle size of SiO₂ colloids will increase,gel phenomenon will occur,and the slurry will become unstable.2.In order to suppress the removal rate of Cu and improve the selectivity of the removal rate of Cu/Ru/TEOS,effect of a new inhibitor 2,2'{[(methyl-1H-benzotriazole-1-YL)methyl]imino}diethanol(TT)on Cu/Ru/TEOS removal rate was studied.The experimental results show that TT has a significant inhibitory effect on the removal rate of Cu,but has little effect on the removal rates of Ru and TEOS.By changing the TT concentration,H₂O₂ concentration,and NH₄⁺concentration,the selection ratio of Cu/Ru/TEOS removal rate can be controlled.When 80 mm NH₄⁺and 1000 ppm TT are added into 5 wt%SiO₂ and 0.15 wt%H₂O₂,the depth of dishing and erosion can be effectively reduced.3.The removal mechanism of Cu/Ru/TEOS by NH₄⁺and TT was studied.Surface elemental analysis(XPS)?electrochemical experiments,and Zeta potential test studies have shown that:NH₄⁺can be oxidized with Ru surface and H₂O₂ to form RuO₂/RuO₄^-/RuO₄^2-and other ruthenium oxides to form a complex reaction with Ru-NH₄ complex which is easily soluble in water,which can effectively improve the removal rate of Ru.NH₄⁺and Cu oxides also form complexes that are easily soluble in water,but undergo double hydrolysis with silicates formed by TEOS hydrolysis.The inhibitory effect of TT on Cu may be due to the formation of covalent and coordination bonds between TT and the metal surface through the lone pair of electrons in the three nitrogen atoms of the 1,2,3-triazole ring,and the formation of close adsorption on the metal passivation layer to protect the metal surface from further oxidation and inhibit metal removal;However,Ru and TOES are more inert than Cu,and relatively weak in passivation with TT,and have little effect on the removal rate of Ru and TEOS.