Study On Copper Interconnect And Tantalum Barrier CMP And Electrochemical Corrosion Characteristics

Chemical mechanical planarization(CMP)is one of the key processes for integrated circuit(IC)manufacturing,and it is the core technology for achieving local and global planarization of multilayer copper wiring.The barrier planarization is the last step in the copper interconnect CMP process,which determines the yield and reliability of IC devices.Tantalum(Ta)has high electrical conductivity and resistance to electromigration,and has good adhesion to Cu.It is widely used as a barrier material for copper interconnects.During the CMP process of the barrier layer,galvanic corrosion will be formed due to the different activities of the two metals,and corrosion on the copper surface will be generated in the presence of corrosive components in the CMP slurry,which affect device performance.To solve the problem of Cu/Ta galvanic corrosion,using FA/O II as a chelating agent,H₂O₂as an oxidant and various surfactants to control galvanic corrosion.Studies have shown that Cu and Ta corrosion increase with increasing FA/O II chelating agent concentration,and decrease with increasing H₂O₂content.The kinetic potential polarization curve(Tafel)shows that FA/O II can reduce the corrosion potential of Cu and Ta differently,which balanced the difference in corrosion potential of both,controlled galvanic corrosion.Open circuit potential(OCP)and electrochemical impedance spectroscopy(EIS)data show that FA/O II plays a role in passivating Ta surface and chelating Cu in the polishing slurry.Dynamic electrochemical analysis shows that the corrosion under polishing conditions is weaker than holding,which attribute to the removal of corrosion and oxidation products on the metal surface by mechanical friction of the polishing pad.When 20 ml/L FA/O II,0.1 ml/L H₂O₂,30ml/L JFCE,0.7 ml/L OA,10 ml/L HOU II,contained in slurry,the Cu/Ta corrosion voltage difference is the smallest,which is-2 m V,reduced galvanic corrosion.In order to solve the problem of Cu surface corrosion,a kind of fungicide 1,2-benzoisothiazolin-3-one(BIT)is used in this paper to reduce the surface corrosion during CMP.Experiments show that BIT can reduce the removal rate of Cu(from 316(?)/min to 210(?)/min),improve rate selection ratio to TEOS,and reduce dishing pits and erosion pits(reduced from 850±100(?)and 1100±100(?)to 350±100(?)and 400±100(?),respectively).By scanning electron microscope(SEM)observation of copper surface,it was found that the BIT can improve the copper surface corrosion.In order to explore its internal mechanism,a Fourier transform infrared absorption spectrometer(FTIR)and X-ray photoelectron spectroscopy(XPS)were used to study the copper surface.The results show that BIT can be adsorbed on the copper surface,thereby reducing the copper removal rate and improving Defects on the copper surface.Finally,the influence of CMP slurry abrasive concentration and polishing process parameters(polishing pressure,rotating speed,slurry flow rate)on the removal rate of Cu/Ta/TEOS was studied.The study found that as the concentration of Si O₂ increased,the removal rates of all three increased.Pressure of process parameters has a major effect on the removal rate of Cu/Ta/TEOS.The removal rate increases with the increase of pressure.