Study On Component Optimization And Mechanism Of Chemical Mechanical Polishing Liquid For Copper

With the rapid development of integrated circuits,technology nodes are shrinking,and metal interconnection is becoming more and more complex,which puts forward higher requirements for the physical properties of interconnecting metals.Copper has low resistivity and superior resistance to electromigration,and has become the main interconnect material for integrated circuits.Chemical mechanical polishing is currently the main technology to achieve interconnect copper planarization.Chemical mechanical polishing is a processing technology that combines the chemical action of additives with the grinding of abrasive,and the polishing liquid is the key to affecting polishing.Most of the copper polishing solutions currently used have problems such as high cost,large pollution,and complex components.With the use of low-k media,low pressure polishing becomes a potential demand.Therefore,environmentally friendly and efficient polishing liquid is one of the keys to copper interconnect technology.In this paper,based on the good polishing effect,and guided by environmental protection and cost-effectiveness,the composition optimization and mechanism analysis of copper chemical mechanical polishing liquid are carried out.First,H₂O₂ and silica are selected as the oxidant and abrasive particles of the polishing liquid.Then,the chemical corrosion effects of different complexing agents on copper are analyzed by electrochemical polarization and static corrosion experiments.Combined with the results of polishing experiments,glycine is determined as a complexing agent.XPS proves that glycine and copper can form glycine-copper,which promotes the participation of copper element in the reaction,which is the reason for the maximum removal rate of the polishing liquid.The film-forming properties of different corrosion inhibitors are studied by electrochemical polarization,impedance and static corrosion experiments.It is found that BTA had a strong film-forming effect,which is the reason for the low removal rate of its polishing solution,while TAZ and PVP have weak passivation protection,and can obtain a large copper removal rate while ensuring good surface quality,and the two had a good synergistic effect.Therefore,the mixture of TAZ and PVP is selected as the corrosion inhibitor.Finally,the removal mechanism model of copper in chemical mechanical polishing is established,and the effect of each additive on copper and the planarization process are analyzed.After determining the additives in the polishing fluid,the influence of each component on the polishing effect is explored through single-factor experiments.The experiment find that with the increase of H₂O₂ concentration,the removal of copper increases and then decreases,the surface roughness decreases first and then stabilized,and the passivation effect of excess hydrogen peroxide is obvious.The increase of silica concentration make the removal first to increase and then stabilize,and the surface roughness first decreases and then increases.The increase of glycine concentration increases the removal rate of copper,and the surface roughness first decreases and then increases.At the same time,it is found that the hydrogen peroxide and glycine system has a better polishing effect when the p H is 7.5.With the increase of the corrosion inhibitor concentration,the surface roughness of the copper sheet decreases,and the removal rate decreases slowly.In order to comprehensively consider the removal rate and surface quality,based on the optimal range of a single factor,the optimal polishing liquid composition is obtained by orthogonal experiments,namely 4 wt.%hydrogen peroxide,6 wt.%silica,1 wt.%glycine,0.1 wt.%TAZ and 0.05 wt.%PVP,p H 7.5.the polishing liquid of this composition has good environmental performance and good chemical mechanical polishing effect.In order to give full play to the effect of the polishing liquid,the influence of the process parameters on the polishing effect is studied through a single-factor experiment.So that the process parameters can be matched with the liquid.Experiments find that increasing the flow rate of the polishing liquid,the rotational speed of the main disk,and increasing the polishing pressure can improve the polishing effect,but if it exceeds a certain range,it will bring more negative effects.The optimal process obtained in the experiment is that the polishing pressure is 13.8 k Pa,the speed of the main plate is 80 r/min,the flow rate of the liquid is 50 m L/min,and the black leather polishing pad is selected.Under these conditions,the surface roughness of the polished copper is 2.07 nm,the removal rate of copper is 1436 nm/min.