Study On The Removal Rate Selectivity Of Copper And Cobalt For Chemical Mechanical Polishing Of 20-14 Nm Integrated Circuit Copper Film

The technology node of integrated circuits continues to reduce,which puts forward higher requirements for the machining accuracy of multi-layer copper wiring applied in giant-large scale integrated circuits（GLSI）.Chemical mechanical polishing（CMP）is the most effective method to achieve global and local planarization of wafer surface in integrated circuits manufacturing,which combines chemical action and mechanical action.Slurry is one of the most important consumables in CMP process,and its performance directly determines the polishing effect and yield of wafer.As the technology node drops down to 20-14 nm,the polishing process of the copper film has changed from the traditional two-step process of bulk copper elimination and residual copper elimination to one step.For the copper film CMP,the removal rate of the barrier material cobalt should be close to zero while the interconnection material copper is removed at a higher removal rate,and the end point of copper film CMP should stop on the barrier material cobalt.Aiming at this problem,a series of experiments and theoretical analysis were carried out to study the influence of different components of slurry on the removal rate selectivity for copper to cobalt.The research results have certain guiding significance for the optimization and the final realization of localization of copper film slurry while obtaining high remocal rate selectivity for copper to cobalt.The specific results are as follows:1.TT-LYK as a new type of soluble corrosion inhibitor was proposed to solve the problems of loose passivation film formed by H₂O₂ on the surface of copper,difficult dissolution of traditional corrosion inhibitors and environmental unfriendly.Under glycine system slurry,TT-LYK can provide an ideal inhibition effect and there is a synergistic effect between TT-LYK and commonly used 1,2,4-triazole.Under the mixed TT-LYK-1,2,4-triazole inhibition in a certain proportion（1:1）,the inhibition effect on copper film was stronger（removal rate dropped to 1988 angstrom/min）and the surface roughness was lower（Sq=1.20 nm）.2.In view of the unclear control mechanism of the main components of slurry on the cobalt removal rate and the removal rate selectivity for copper to cobalt,the effects of different components（abrasive concentration,H₂O₂ concentration,corrosion inhibitor）and the p H value of slurry on the unmanageable cobalt removal rate were studied.The results showed that the removal rate of cobalt could be effectively reduced by lower abrasive concentration（0.50 wt%）,higher H₂O₂ concentration（30 ml/L）,higher p H value of slurry（10.50）,and the introduction of appropriate corrosion inhibitor（500 ppm TT-LYK）.Under this optimized slurry,the removal rate selectivity for copper to cobalt was 212:1,meeting the requirement of industrial application of more than 100:1.On this basis,through the mixed use of organic alkali TEAH and inorganic alkali KOH,the stability of the slurry can be improved（stable for at least 3days）while meeting the requirement of the removal rate selectivity for copper to cobalt.3.According to the requirements of environmental protection for slurry,a new green additive chitosan CTS was proposed on the basis of previous research.CTS with different concentrations can play the roles of bactericidal properties,improving dispersion,complexing metal ions,corrosion inhibition,reducing surface roughness in slurry,the introduction of appropriate amount of CTS can increase the removal rate selectivity for copper to cobalt from 24:1 to 67:1,and relevant mechanisms were analyzed.At the same time,the removal rate selectivity for copper to ruthenium can be increased from 123:1 to 451:1 when ruthenium is used as barrier material under lower technology nodes,which shows that CTS can be used as effective corrosion inhibitor of ruthenium.Such study provides theoretical guidance for its application in CMP industry.