Study On The Selectivity Of Removal Rate Of Barrier CMP For Integrate Circuit Cobalt Plugs

In recent years,with the rapid development of GLSI,the process technology node has been upgraded to 7nm and below.The traditional plug metal tungsten can't meet the needs of modern industry because of its rapidly increasing resistance in the deposition process,so a new plug metal cobalt(Co)with low resistivity(6.63??·cm)can be used instead.Chemical mechanical planarization(CMP)is one of the key steps in IC manufacturing process,and it is the most effective way to achieve partial or global planarization of wafer surface so far.Barrier CMP is the last process of multilayer copper wiring,the unbalance of the removal rate of the barrier materials will directly lead to the reliability of the devices such as dished pits and etched pits.In order to improve the removal mechanism of barrier materials under the new technology node and reduce the removal rate selectivity of materials,the related theoretical analysis and experimental research are carried out in this paper.The main achievements are as follows:1.Aiming at the problem that the removal mechanism of Cobalt plug and barrier material is not perfect,the material removal and reaction process under different influencing factors are studied.The formation process of oxide on the surface of the material was studied by the theory of electrode potential,the wettability of the polished material was investigated by the means of contact angle characterization,the surface composition of the material was analyzed by X-ray photoelectron spectroscopy,finally,the removal mechanism of Co/Ti/TEOS in the potassium tartrate hemihydrate-hydrogen peroxide system's slurry was revealed.The results lay a theoretical foundation for reducing the removal rate selectivity of Co/Ti/TEOS.2.In view of the higher removal rate selectivity of Co/Ti/TEOS in the process of barrier polishing,the influence of potassium tartrate hemihydrate-hydrogen peroxide system's slurry on the polishing rate of various materials was studied.Tartaric acid can complex cobalt ion and titanium acyl ion;potassium ion can attract the negative charge around the silica sol particles;hydrogen peroxide can intensify the formation of passive film on the surface of Cobalt and accelerate the production of titanium acyl ion.The removal rate selectivity of Co/Ti/TEOS can be controlled by using the slurry' system.The dominance of different factors on the removal rate of Cobalt and Titanium was determined by orthogonal experiment.When the pH of the slurry is 10,the concentration of silica sol,potassium tartrate hemihydrate and hydrogen peroxide are 4wt%,2.5wt% and 0.15wt%,respectively,the removal rate selectivity of barrier is effectively reduced.The results provide technical support for the study of barrier CMP with 7nm node and below.3.In view of the poor surface quality of Cobalt plug after polishing,the influence of surfactant on the surface roughness of Cobalt was studied by using the theory of mass transfer and retention layer.After adding 0.8wt% of non-ionic surfactant(jfc-e)into the optimized slurry,the surface roughness(S_q)of Cobalt film was reduced from 2.34 nm to 0.39 nm,and the surface heterogeneity of Cobalt film was3.85%.The results of this experiment have certain guiding significance for the practical industrial application.