Investigation On Cu/Ru Galvanic Corrosion Of Barrier Layer Ru Chemical Mechanical Polishing For GLSI Multilayer Copper Interconnection

As the technology nodes of great large scale integrated circuits(GLSI)decrease to 7nm and below,ruthenium(Ru)has been condidered a candidate to replace the traditional barrier layer tantalum/tantalum nitride(Ta/Ta N)due to its excellent characteristics.Due to the large corrosion(gc)potential difference between the Ru and Cu,during the chemical mechanical planarization(CMP)of the barrier layer in the copper interconnect.The galvanic corrsion would be ocuured when contact with the slurry,it will affects the reliability and yield of the device.In this paper,the issue of Cu/Ru galvanic corrsion during Ru CMP applied in copper interconnect was studied,and the mechanism of Cu/Ru gc control is revealed.The main contents are as follows:(1)When potassium periodate(KIO₄)is used as an oxidant,the effects of KIO₄concentration and p H on galvanic corrosion between Cu/Ru was firstly studied,the results show that when the concentration of KIO₄is 20 m M and p H=8,the corrosion potential difference(?_Ecorr)between Cu/Ru are lager,it is about 0.565 V,and there is severe galvanic corrosion between Cu/Ru.Three kinds of inhibitors was applied to reduce gc,such as benzotriazole,1,2,4-triazole,2,2'-[[(methyl-1H-benzotriazol-1-yl)methyl]Amino]diethanol(TT-LYK)were compared,the results show that when TT-LYK is used as an inhibitor,the?E_corrbetween Cu/Ru is the smallest,indicating that TT-LYK has the best inhibition effect.Finally,the effect of TT-LYK concentration on Cu/Ru gc and its mechanism were studied.The experimental results show that the?_Ecorrbetween Cu/Ru decreases with increasing TT-LYK concentration.When the solution ratio is 5 wt%Si O₂,20 m M KIO₄,0.1 wt%TT-LYK,and the p H=10,the?_Ecorrbetween Cu/Ru is 0.017 V,and the CMP rates are 414(?)/min and 430(?)/min,respectively.At this time,the galvanic corrosion between Cu/Ru is controlled,and the removal rate selection ratio is desirable.(2)The effects of H₂O₂concentration and p H on galvanic corrosion between Cu/Ru were studied in H₂O₂-based slurry.The results show that the?E_corrbetween Cu/Ru in H₂O₂solution is small,but the CMP rate of Ru is too low(107(?)/min).The effects of three accelerator(potassium chloride,guanidine carbonate(GC),ammonium sulfate)on the corrosion and removal rate of Cu/Ru galvanic couple were compared,Finally GC was selected as the accelerator.The effects of GC and TT-LYK concentrations on Cu/Ru galvanic corrosion were studied.The results show that the addition of GC can increase?_Ecorrof Cu/Ru,and addition of TT-LYK makes Cu/Ru have a smaller?_Ecorr.When the solution composition is 5 wt%Si O₂,0.15 wt%H₂O₂,40 m M GC,0.1 wt%TT-LYK,and the p H=10,the?_Ecorrbetween Cu/Ru is-0.075V,the galvanic corrosion between Cu/Ru was contolled,and the CMP rates are 472(?)/min and 498(?)/min,respectively.Also has a good rate selection ratio.(3)Through electrochemical experiments and X-ray photoelectron spectroscopy(XPS)detection experiments,the control mechanism of Cu/Ru galvanic corrosion by TT-LYK was analyzed and studied.The results show that TT-LYK reacts with Cu and Ru,and the reactants form a dense passivation film on the surface of Cu and Ru by physical and chemical adsorption.The existence of the passivation film prevents further corrosion of Cu and Ru,thereby inhibiting galvanic corrosion between Cu/Ru.