Research On Microchemistry And Material Removal During Cu CMP Based On ReaxFF

The invention and development of copper interconnect technology plays an important role in the development of integrated circuit technology.Among them,Chemical Mechanical Planarization/Polishing?CMP?is the most common technical means for obtaining global or partial planarization in copper interconnect technology.At present,the study on copper CMP is mainly using experimental research.However,the explanation of chemical reaction mechanism and material removal form in this process is not clear enough.Therefore,the reaction molecular dynamics method is used to monitor the CMP process in real time with visualization software.The microscopic chemical reaction,atomic bonding method and material removal are described from the atomic perspective.And to some extent,theoretical supplements are provided for experimental phenomena.The copper CMP model containing was constructed based on ReaxFF reaction molecular dynamics method.The microscopic chemical reaction of each substance and copper atom removal were studied by simulating copper CMP process.The results indicated that there are both atomic adsorption and dissociation adsorption between H₂O?H₂O₂ molecules and surface copper atoms,and the main products are Cu-H₂O and Cu-OH in the chemical reaction stage.The copper atoms are mainly removed in the state of clusters by the breakage of Cu-Cu bonds and Cu-O bonds during the sliding of the abrasive grains.The four simulations were carried out to investigate the microscopic chemical action of H₂O₂ and glycine in copper CMP with four different polishing slurry conditions:in pure water,in aqueous H₂O₂,in aqueous glycine and in aqueous H₂O₂+glycine respectively.The simulation results showed that the product on the copper surface in pure water state is Cu-H₂O,while they are mainly Cu-H₂O and Cu-OH in aqueous H₂O₂.And the increasing of H₂O₂ content can inhibite the molecular adsorption and promote the dissociative adsorption of H₂O molecules.When the glycine is added to the polishing slurry,the copper complex?Cu-C₂H₅O₂N?is formed,and the molecular adsorption of H₂O molecules are inhibited.In addition,H₂O₂ and glycine will cause some Cu atoms to form bumps on the surface,which is conducive to the atom removal,while there are no bumps of copper atoms in pure water.In terms of atomic removal,the amount of copper atoms removed is the least in pure water,while it is the most in aqueous H₂O₂+glycine.When the content of H₂O₂ in the polishing slurry is different,the amount of copper atom removal increases first and then decreases as the content of H₂O₂ increases.The reaction molecular dynamics method was used to simulate the Cu CMP process under different polishing pressure and polishing temperature.The results showed that with the increase of polishing pressure,the interface friction force and the number of removed atoms increased.When the polishing temperature increases,the chemical activity of slurry is promoted and the amount of Cu atom removal is increased.In order to verify the applicability of the reaction molecular dynamics method for simulating Cu CMP experiments,Cu CMP experiments under two polishing conditions were carried out.The experiment results showed that when H₂O₂ is added to the polishing slurry,the material removal rate can be increased and the surface roughness after polishing can be reduced.The simulation results also indicated that the addition of H₂O₂ in the polishing solution increases the amount of copper atom removal.